equal pairs, each 0.2 m long. In order to make them visible the lengths of its sides alone.

ne. The exact arrangement of

at a distance they are painted alternatively black or white triangles to be adopted depends upon the shape and
and red and white or red, white and black successively. configuration of the ground, and the natural obstacles
When they are at a considerable distance red and white met with. If a point is located by the intersection of two
or white and yellow flag about 25 cm square should be arcs, its displacement due to errors in the radii is a
fastened at the top. minimum if the arcs intersect at 90°.The three sides of a
triangle being equally liable to error, each of the three
3 Ranging poles angles of a triangle should be nearly 60°. i.e. the triangle
The ranging poles are similar to the ranging rods. But should be equilateral. An equilateral triangle can
are of heavier section. They vary in length from 4-10 cm therefore, be more accurately plotted than an obtuse-
or more and are used in the case of very long line. angled triangle. Hence the best shaped triangle is
equilateral and it is desirable to approximate to this form
Chain Surveying in order that distortion due to errors in measurement and
plotting should be minimum.
Land Surveying: Land surveys are made for one or more
of the following purposes: The framework should, therefore, consist of triangles
which are as nearly equilateral as possible, such triangles
I To secure data for exact description of the boundaries being known as well conditioned, or well-shaped. A
of a piece of land (or tract). triangle is said to be well conditioned or well-proportioned
when it contains no angle smaller than 30° and no angle
II To determine its area.
greater than 120°. III - conditioned triangles (Fig 8) having
III To secure the necessary data for making a plan. angles less than 30° or greater than 120° should always
be avoided. If however, they are unavoidable, great care
IV To re-establish the boundaries of a piece of a land
must be taken in changing and plotting.
which has been previously surveyed, and
V To divide a piece of land into a number of units.

There are two general methods of land surveying

1 Triangulation and
2 Traversing

1 Triangulation Survey: Triangulation is the basis of

Chain and Compass Traversing: In traverse
trigonometrical or geodetical surveys. The term
surveying the directions of survey lines are fixed by
triangulation when used without qualification, denotes a
angular measurements and not by forming a network of
system of surveying in which the sides of the various
triangles as is done in chain surveying.
triangles are computed from
A traverse surveying is one in which the framework
i a single line measured directly, called the base line,
consists of a series of connected lines, the lengths and
and
directions of which are measured with a chain or tape,
ii the three angles of each triangle measured accurately and with an angular instrument respectively. The routine
with a theodolite. of chaining and offsetting is the same as in chain
surveying. The running of check lines is not necessary.
Chain triangulation or chain surveying: It is the system
of surveying in which the sides of the various triangles A traverse may be classed as (a) closed, and (b) unclosed
are measured directly in the field and no angular or open.
measurements are taken. The simplest kind of surveying
is the chain surveying. It is most suitable when. a Closed Traverse: A traverse is said to be closed when
a complete circuit is made, i.e. when it returns to the
I The ground is fairly level and open with simple details. starting point forming a closed polygon as in Fig 9., or
when it begins and ends at point whose positions on
II Plans are required on a large scale such as those of
plan are known The work may be checked and
estates, fields, etc.
“balanced”.
III The area is a small in extent.

It is unsuitable for large areas, and areas crowded with

many details or difficult or wooded country. The principle
of a chain survey is triangulation. It consists of the
arrangement of framework of triangles since a triangle is
the only simple plane figure, which can be plotted from

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.1.41 7
Construction Related Theory for Exercise 2.2.46
Draughtsman Civil - Compass surveying
Identification and Parts of instruments in compass survey
Objectives : At the end of this lesson you shall be able to
• state about traversing
• state types of compass
• name the prismatic compass and construction
• construction of survey’s compass.

Traversing The prismatic compass: It is the most convenient

portable magnetic compass, which can either be used
Traversing is that type of survey in which a number of as a hand instrument or can be fitted on a tripod. The
connected survey lines from the frame work and the main parts of prismatic compass are shown in Fig 3.
directions and lengths of the survey line are measured
with the help of an angle measuring instrument and a Construction (Fig3)
tape respectively. When the lines form a circuit which
ends at the starting point is called closed traverse. Fig 1.
If the circuit end else where it is said to be an open
transverse. (Fig 2)

Compass: A compass is a small instrument which

consists essentially of a magnetic needle, a graduated
circle and a line of sight. When the line of sight is directed • The prismatic compass consists of cylindrical metal
towards line, the magnetic needle points towards box (1) of 8cm to 12 cm diameter in the centre of
magnetic meridian and the angle which the line makes which is a pivot (2) carrying a magnetic needle. (3)
with the magnetic meridian is read at the graduated circle. which is already attached to the graduated aluminium
ring (4) with the help of an agate cap (5)
The compass cannot measure the angle directly. If it is
desired to find out the angle between the two lines, firstly • The ring is graduated to half a degree and is ready by
their angles with the magnetic meridian are determined a reflecting prism (6) which is protected from dust,
separately and the difference of the two valves is found moisture etc. by the prism cap (7)
which is equal to the angle between the lines. • Diametrically opposite to the prism is the object vane
(8) hinged to the box side and carrying a horse hair
Types of Compass: The two forms of the compass (9) with which an object is bisected.
commonly used are:
• The eye is applied at the eye hole below the sighting
1 The prismatic compass slit (10)

2 The surveyors compass • The graduations on the ring can be observed directly
by the eye after they are reflected from the diagonal
of the prism.

25
• The graduations can be made clearly visible by The bearing shows 330° at the observer’s end under the
adjusting the prism to the eye sight by the focusing prism (ie at the south end) (Fig 5)
screw (11)
• Both the horizontal and vertical side faces of the prism
are made convex to give magnified readings.
• To prevent undue wear of the pivot ,point the object
vane is brought down on the face of the glass cover
(12) which presses against a lifting pin (13)
• The needle is then automatically lifted off the pivot by
the lifting lever (14)
• To damp the oscillations of the needle, before taking
a reading and bring it to rest quickly the light spring
break (15) attached to the inside of the box is brought
in contact with the edge of the ring by gently pressing
inward the brake pin (16)
• If the bearings of very high (or) very low objects are Surveyors Compass: It is similar to prismatic compass
taken the reflecting mirror (17) which slides on the except with a following few modification (Fig 6)
object vane is tilted and image is bisected by the horse
hair.
• A pair of sun glasses (18) shall have to be inter
proposed between the slit and colored vane when the
sun or luminous of objects is to be bisected.
• A metal cover fits over the glass cover as well as the
object vane when the compass is not in use.
• In the prismatic compass (Fig 4a) graduations are
marked on the ring in a clockwise direction with 0 or
360 at south end of the needle.
• So that 90 is marked at the west 180 at the North and
270 at the east.
• The figures are written upside down as in Fig (4b)

– The graduated ring is directly attached to the circular

box and not with the magnetic needle.
– The magnetic needle floats freely over the pivot.
– No prism is attached to the eye vane and it is having a
narrow vertical slit.
– Readings are taken directly with naked eye against
the north end of the needle.
– The right is graduated in quadranted system of having
0° at north and south ends, 90ˆ at East and west
ends. Fig 6a shows when the line of sight towards ‘B’
and the bearing is N 30° E.

Bearing of a line: It is the horizontal angle which a line

make with some reference direction also known as
meridian. The reference direction may be any of the
following (Fig.7)
• The greatest advantages of prismatic compass is that – True meridian
both sighting the object as well as reading circle can
be done simultaneously without changing the position – Magnetic meridian
of the eyes. – An assumed meridian

26 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.2.46
Comparison between prismatic compass and surveyors compass

No Item Prismatic compass Survryor’s compass

1 Magnetic needle The needle is broad type and needle The needle is of edge bar type of
does not act as index. needle and acts as the index also.
The graduated ring is attached to the
2 Graduated ring The graduated ring is attached with box and not the needle. The ring ro-
the needle. The ring does not rotate tates along with the line of sight.
along with the line of sight.
The graduations are in Quadrantal
The graduations are in whole circle bearing system having 0°at North
bearing system, having 0° at south system having 0°at North and South,
end 90°at west, 180° at North and 90° at East and West. East and west
270° at East. are interchanged.
The graduations engraved are in- The graduations engraved are erect.
verted.

3 Sighting vane The object vane consists of metal The object vane consists of a metal
vane with a vertical hair. vane with a vertical hair.

4 Reading The reading taken with the help of a The reading is taken by directly see-
prism provided with the eye vane. ing through the top of the glass.
Sighting and reading can be done Sighting and reading cannot be done
simultaneously from one position of simultaneously from one position of
the observer. the observer.

5 Tripod It is used with or without Tripod. It cannot be used without a Tripod

An assumed or Arbitary meridian: Arbitary meridian is

any convenient direction towards a permanent and
prominent mark or signal such as a church spire or top of
a chimney. Such meridians are used to determine the
relative positions of lines in a small area.

Arbitary Bearings: Arbitary bearings of a line is the

horizontal angle which it makes with any arbitrary meridian
passing through the one of the extremities or the horizontal
angle between a line and this arbitrary meridian is called
arbitrary bearing of the line.
True Meridian: The meridian of a place is a direction Designation of Bearings: The bearings are expressed
indicated by an imaginary circle passing round the earth in the following two ways.
through that place and the two north and south poles.
– Whole circle bearings.
True Bearing: The horizontal angle between a line and
the true meridian is called true bearings of the line. It is – Quadrantal bearings.
also called as azimuth.
Whole Circle bearing (W.C.B): In this system, the
Magnetic Meridian: The direction indicated by a freely bearings of a line, is measured from the magnetic north
suspended and properly balanced magnetic needle in clockwise direction. The value of the bearing thus varies
unaffected by local attractive forces is called the magnetic from 0° to 360°. The prismatic compass measures the
meridian. bearings of lines in the whole circle system.

Magnetic Bearings: The horizontal angle which a line Referring Fig 8 the W.C.B of AB is θ1; of AC is θ1 and
makes with this meridian is called magnetic bearings or AC is θ2; AD is θ3 and of AF is θ 4.
simply bearings of the line.

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.2.46 27
 trigonometrical function is known as reduced bearing
(R.B)

i Referring Fig 8, W.C.B system, the conversion of

W.C.B into R.B can be expressed in the following table.
Table 1
Line W.C.B Rule for R.B Quadrant
between

AB 0° and90° R,B = W.C.B NE

AC 90º and R,B =180º - SE

180º W.C.B
AD 180º and R.B = W.C.B - SW
270º 180º
AF 270º and R.B = 360º - NW
360º W.C.B
The Quadrantal bearings: In this system, the bearings
of a line is measured east ward or westward from north
ii Referring Fig 9 the conversion of R.B into W.C.B can
or south whichever is nearer. Thus both North and South
be expressed in the following table.
are used as reference meridians and the directions can
be either clockwise or anticlockwise depending upon the Table 2
position of the line. These bearings are observed by
surveyors compass. Line R.B Rule for W.C.B W.C.B between
AB NαE W.C.B = R.B 0 AND 90
Referring Fig 9 the QB of the line AB is ∝ and it is written
as N∝ E AC Sβ E W.C.B = 180- R.B 90 AND 180
AD SθW W.C.B = 180+ R.B 180 AND 270
AF N φW W.C.B = 360 - B 270 AND 360

Fore Bearings and Back Bearings: Every line has two

bearings, observed one at each end of the line. The
bearing of a line taken in the progress of the survey or in
the forward direction is the fore or forward bearing (F.B)
of the line. While its bearing taken in the reverse or
opposite direction is known as reverse or back bearing
(B.B)

Whole Circle bearing system

Fig 10 shows. The bearing of line AB expressed in the

direction A to B is the F.B of AB.

The bearing of Line AC is band it is written as S β E.

Similarly, the bearing of line AD and AF are written as S θ

W and N φ W

Conversion of Bearings from one system to other

system

Reduced bearing

When the whole circle bearings exceed 900 , then it is

to be converted or reduced to quadrantal bearing system
which has the same numerical values of the

28 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.2.46
Plotting of a compass traverse

Before plotting traverse on the drawing sheet, first to draw

a rough sketch on the paper.

From this we can able to know the size and shape of the
plan and also the best way to arrange it on the drawing
sheet.

From the observed bearings, corrected bearings are

calculated before plotting.

The following methods are used for plotting a traverse

survey.

By parallel meridian through each station (Fig 1)

From the corrected bearings, the included angles are
calculated.

From the starting station A, draw a line representing the

magnetic meridian.

From A, draw the bearing of the line AB, and cut off the
length AB according to scale, thus fixing of the station ‘B’

From B draw the included angle ABC.

The same process may be repeated at each successive

stations.

By paper protractor (Fig.3)

First fix the position of the starting point P on the paper.

From this point P draw the magnetic meridian.

Plot the bearing of the line PQ with the protractor.

Cut the length of the line PQ with suitable scale.

Now the station point Q is fixed.

From Q, draw a line which is parallel P to magnetic

meridian.
First mark any point ‘O’ on the paper and draw the bearing
of each line with reference to the magnetic meridian by
Plot the bearing of the line QR and cut off the length of
using large circular paper protector is shown in Fig a.
line QR.
Transfer the direction of all the lines to their proper
Repeat the same process until all the lines are drawn.
positions and taking length of each lines is shown in
If the traverse is a closed one the last line must coincise Fig b.
with the starting station P.
By rectangular co-ordinate method (Fig 4)
If not the error is called as closing error.
Firstly, the points of traverse are plotted by their
By included angle method (Fig 2) coordinates with respect to x-axis and y-axis. The x axis
and y axis are intersecting at ‘O’
Before plotting the included angle method of the corrected
bearings are calculated first, from the observed bearings. • The line OX is representing the magnetic meridian.
• Every point is plotted independently with reference to
the axes.

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.2.47 - 50 53
 Adjustment

1 Draw a straight line AA’ equal to the perimeter of the

traverse to a suitable scale.
2 Draw A’A” parallel and equal to the closing error AA’
Firstly, the co-ordinates of each point are calculated. and join AA”.
3 Draw a parallel line through B, C, D and E to meet the
This method is mainly used in plotting of traverse by using B’, C’, D’ and E’
Theodolite instrument.
4 Draw parallel lines through the plotted station B, C, D
• It is more accurate method of plotting. and E and plot the errors equal to BB’, CC’, DD’ and
EE’ in direction parallel to A’A”.
• In this method the errors are not accumulate.
5 Join the points AB’C, D’E A to get the adjusted traverse.
Closing Error and its graphical Adjustments: While
plotting a closed traverse the starting and the ending Sources of Error in Compass Survey:
points will coincide otherwise if the ending points fails to
meet with the starting one is called the closing error or The errors in compass instrument may be:
error of closure.
1 Instrumental errors.
The closing error occurs due to wrong 2 Errors due to manipulation and sighting.
measurement of lengths and bearing of lines
in the field are due to faulty plotting. 3 Errors due to external influence.

When the closing error exceeds permissible I Instrumental Error:

limit, the field work is repeated. But the error
is found to be within the permissible value, the 1 The needle not being straight.
traverse may be adjusted. 2 The pivot being bent.

When the angular and linear measurements are of equal 3 The needle having lost is magnetism.
precision graphical adjustment of the traverse may be 4 The pivot point being blunt.
used. This method is based on the Bowditch’s rule.
5 The needle neither moving quite horizontally nor
The correction may be applied both lengths as moving freely on the pivot due to the dip of the needle.
well as to bearings of the lines in proportion to 6 The plane of sight not being vertical.
their lengths. 7 The vertical hair being to thick or loose.

The adjustment of a compass traverse graphically, may 8 The line of sight not passing through the centre of the
graduated circle.
be made as under.
II Errors due to manipulation and slighting
Procedure (Fig 5)
1 Inaccurate centering of the compass
Let ABCDEA be a closed traverse as plotted from the
observed magnetic bearings and linear measurements 2 Carelessness in reading
of the traverse lengths. A is the starting station and A is
3 Carelessness in recording
the location of the station a as plotted. Hence, A’ A is the
closing error. 4 Improper bisecting and ranging.
5 Inaccurate levelling.

54 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.2.47 - 50
III Errors due to external influences. To ascertain if the needle is sluggish, take a reading
in any position of the needle being in rest. Then
1 Variations in declination displace the needle by bringing near it a piece of steel
or bunch of keys etc. and let it come to rest and then
2 Local attraction again take the reading.
3 Magnetic changes. The reading will be the same if there is no friction on
the pivot and the needle is not sluggish. If reading is
4 Irregular variations due to magnetic storms not the same, then the pivot point should be sharpened
earthquakes etc. by a fine oil stone and the needle should be
remagnetised by a bar magnet.
Testing and adjustments of the compass
3 To see if the sights are fixed diametrically opposite to
The compass should be tested and adjusted as explained each other, stretch a fine horse-hair between the
below. sights. It will pass over the N and S marks.
4 To detect if there be any error due to careless working
1 When the compass is levelled the needle or ring
on external influence, take the fore and back bearing
should be horizontal if not, slide the rider on the higher
of a line and this differ exactly by 180º if the work is
end of the needle to make it horizontal.
correct and there is no external influence.
2 The needle should be sensitive so that it may not come
to rest in a direction other than the magnetic meridian.

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.2.47 - 50 55
Construction Related Theory for Exercise 2.3.51 - 2.3.52
Draughtsman Civil - Plane table surveying
Instrument used in Plane table surveying
Objectives : At the end of this lesson you shall be able to
• state plane tabling
• name the Instruments and Accessoriees used in plan tabling
• state the construction and and uses of Instruments and Accessories of plane tabling
• explain about Levelling, centering and orientation in plane tabling
• explain the methods of plane tabling.

Plane tabling: Plane tabling is graphical method of

surveying in which field observations and plotting are done
simultaneously on a plane table.

It is most suitable for filling in the various details between

the stations previously fixed by triangulation.

It is commonly used for preparing small scale mapping

or medium size mapping. This type of survey is employed
when great accuracy is not required such as
Topographical surveys.

Instruments used in plane tabling

- Plane table with Tripod

- Alidade
Accessories used in plane tabling
- Spirit level
- Trough compass
- Plumbing fork with plumb-bob & water proofing cover.

Plane Table with Tripod etc: Plane table is made of

well-seasoned good quality teak or pine wood and is
available in different sizes.

- Small: 50cm x 40cm x 1.5cm

- Medium: 50cm x 50cm x 1.5cm
- Large: 75cm x 60cm x 1.5cm

It is mounted on a Tripod in such a way that it can be – Plain Alidade

levelled, rotated about a vertical axis and clamped in any
position. The upper surface of the board must be perfectly
– Telescopic alidade
plane. The tripod is generally of the open frame type and Plain Alidade:Itconsists of a metal or wooden rule with
can be folded (Fig 1) for convenience of transportation. two vanes at the ends. Vanes are hinged and can be
folded on the rule when the alidade is not in use (Fig 2)
Qualities of a Good Plane Table:
One of the vanes known as sight vane is provided with a
- The butterfly nuts which clamp the legs to the clamping narrow slit with three holes, one at the top, one at the
head should not be free. bottom and one in the middle.
- The clamping assembly should fit the plate at the
bottom of the plane table. The other vane which is known as object vane is open
and carries a hair stretched between the top and bottom
The Alidade:The Alidade is a straight edge with some of the slit. With the help of the slit, a definite line of sight
form of sighting device. Two types of alidades are may be established parallel to the ruling edge of the
generally used. alidade. The alidade can be rotated about the point which

56
represents the location of the instrument station on the Telescopic Alidade: It is generally used when it is
sheet so that the line of sight passes through the station required to take inclined sights. The telescope increases
sighted. The two vanes should be perpendicular to the the range and accuracy of the sights. It consists of a
ruler as well as surface of the plane table. The working small telescope with a level tube. A graduated scale is
edge of the alidade is called fiducial edge. mounted on a horizontal axis. The horizontal axis rest
on a A-frame which is supported on a heavy metal ruler.
The plain alidade can be used when the elevations or One side of the ruler is used as working edge. (Fiducial
depressions of the objects are low. edge) along which lines may be drawn. The angles both
elevation and depression can be read on the vertical circle
(Fig 3).

Sprit Level:A spirit level consists of a small metal tube

which contains a small bubble at centre. The Base of
spirit level must be flat so that it can be laid on the table.
When table remains central, the table is truly level (Fig 4)

Trough compass or magnetic compass: A box

compass consists of a magnetic needle pivoted at its
centre freely. It is used for making the direction of the
magnetic meridian on the sheet. So it is also used for
orienting the plane table to magnetic north. Both the
edges of a compass are straight, and bottom surface is
flat. The magnetic needle should be fairly sensitive and
play freely (Fig 5)

Plumbing fork with bob: The fork consists of a hair pin

shaped light metal frame having two arms of equal length,
in which a plum-bob is suspended from the end of the
lower arm (Fig. 6)

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.3.51 - 52 57
The fitting can be places with the upper arm lying on the
top of the table and the lower arm below it, the table being
centered when the plumb-bob hangs freely over the
ground mark and the pointed end of the upper arm
coincides with the equivalent point on the plan.

It is used for centering the table over the point or station

occupied by the plane table when the plotted position of
that point is already known on the sheet. In the begining
of the work it is meant for transferring the ground point
on to the sheet so that the plotted point and the ground
station are in the same vertical line.

Setting up the plane Table

The setting up the plane table involves three operations.

1 Levelling the plane Table Orienting the plane table: It is the process of putting
2 Centering the plane Table the plane table in to some fixed direction so that the line
representing a particular direction on the plan is parallel
3 Orienting the plane Table. to the direction on the ground. Orientation is necessary
Levelling the plane Table: In this operration, the table when more than one instrument station is to be used. If
top is made truly horizontal. For rough and small scale orientation is not done, the table will not be parallel to
works, levelling of table can be done by eye estimation, itself at different positions resulting in an overall distortion
and for large scale works levelling of table can be done of the map. The process of centering and orientation
by using spirit level. The levelling is specially important are dependent on each other. For orientation, the table
in hilly terrain where some of the control points are will have to be rotated about its vertical axis, thus
situated at the higher level and some other at lower level disturbing the centering.
(Fig 7).
Orientation by back sighting (Fig 9)

The table is set up on the station B and it is represented

as ‘b’ on the paper which is plotted by means of a line ab
from the back station A. Now, the orientation is bringing
ba on the paper over. BA on the ground. Placing of alided
on ba, turn the table till the station ‘A’ is bisected. The
clamp the load in this position.

Orientation by magnetic needle

For orientated the table at any station other than the first
station, but the trough compass on the meridian already
drawn on the paper at the first station and turn the table
till the ends of the needle are opposite the zeros of the
scale towards north – south direction. At this position
clamp the board. This is the quick method but unsuitable
Centering the plane Table: In this operation, the for magnetic area.
location of the plane table station, on the paper is brought
exactly vertically above the ground station position. For
rough works exact centering of the station is not
necessary but for large scale maps and accurate works
exact centering is required . (Fig 8)

58 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.3.51 - 52
Method of plane table survey
Objectives : At the end of this lesson you shall be able to
• methods of plane table survey
• radiation method of plane table survey
• intersection method of plane table survey.

The following arethe four methods of plane table survey.

Note: This method is suitable for the survey
of small areas which can be commanded from
• Radiation
single station.
• Intersection
·It is also useful in combination with other methods for
• Traversing
surveying details within a tape length from the station.
• Resection
Intersection Method:
Radiation Method
• In this method of the positions of the points are fixed
The Plane table is set up at only one station and various on the sheet by the intersection of the rays drawn
points are located by radiating lines drawn from the from two instrument stations.
instrument station to each of the points and plotting to
• The line joining these two stations are termed as base
scale along the ray drawn with the distance measured
line.
from the station to the point sighted.
• This is the only linear measurement taken in the field.
(Fig 1)
• It is largely employed for locating details and for
locating the points to be used subsequently as
instrument stations.
• It is also used for plotting the distant and inaccessible
objects, broken boundaries, river etc.
• It is more suitable for surveying hilly country where it
is not possible to measure the horizontal distances,
difficult to measure the horizontal distances.

Procedure (Fig 2)

• Select a point P such that all the points to be located

are visible from the point.
• Set up and level the table at P and clamp it.
• Select a point ‘p’ on the sheet and make it vertically
above ‘P’ on the ground by the use of ‘U’ frame.
• The point ‘p’ represents on the sheet as the station
‘P’ on the ground.
• Mark the direction of the magnetic meridian with the
trough compass in the top corner of the sheet.
• With the alidade touching ‘p’ sight the various points
A, B, C, D and E etc to be located and draw radial
lines towards them along the fiducial edge of the
alidade.
• Select two points A and B on the ground, so that all
• Measure the radial distance PA, PB, PC, PD and PE
points to be plotted are visible from both the station.
with the tape.
• Set up and level the plane table at station A and mark
• Plot the distance to scale along the corresponding
a suitable point ‘a’ on the paper, so that it is vertically
rays. Join the points a, b, c, d, e on the sheet.
above the instrument station A on the ground.
• Mark the direction of magnetic meridian on the top
corner of the sheet by means of a trough compass.

Construction: Draughtsman Civil - (NSQF LEvel -5): Related Theory for Exercise 2.3.51 - 52 59
• With the alidade touches on the point ‘a’ sight the • Orient the table by placing the alidade along ‘ba’
station B and other points 1,2,3 etc to be located and turning the table till the line of sight stricks ‘A’ and
draw rays towards them. clamp it.
• Make the respective lines by letter b, 1,2,3 etc to avoid • With the alidade pivoted on ‘b’ draw rays sighting
confusion. towards the same objects (ie) 1,2,3,4 etc.
• Measure the base line AB with a steel tape or chain • The intersections of these rays with the respective
cut off distance ‘ab’ to scale along the ray from ‘a’ B. rays from “a” determine the positions of the object
1,2,3,4 on the sheets.
• This is the position ‘b’on the sheet of the station ‘B’
on the ground.
• Shift the instrument and set it up and level at ‘B’ such
that the point ‘b’ is exactly above the point B on
theground.

Traversing method of plane table survey

Objectives : At the end of this lesson you shall be able to
• state traverse method of plane table survey
• conduct traverse method of plane table survey.

Traversing • Measure the distance AB and Scale off ‘ab’. Thus

fixing of the position of ‘b’ on the sheet which
• This is main method of plane tabling and similar to represents the station ‘B’ on the ground.
that of compass or Theodolite traversing.
• Locate the near by details by offsets taken in the usual
manner or by radiation and distant objects by
• It is used for running survey lines of a closed traverse
intersection method.
or open traverse.
• Shift the table and set it up at ‘B’ with ’b’ over ‘B’ and
• The details may be located by offsets taken in the
orient it by placing the alidade along ba, turning the
usual manner (i.e.) by the radiation or by inter section
table till the line of sight strikes ‘A’ and then clamp it.
method of plane tabling.
• With the alidade touching ‘b’ sight ‘C’ draw a ray.
Procedure
• Measure the line BC and cut off ‘bc’ to scale.
• Select the traverse station A, B, C, D etc. on the • Locate the surrounding details are taken before in
ground. station ‘B’.
• Set up the table over one of them say ‘A’ select a • Proceed similar to the other stations, in each case
point ‘a’ suitably on the sheet. Level and centre the orienting by a back sight before taking the forward
table over ‘A’. sight until all the remaining stations are plotted.
• Mark the direction of the magnetic meridian on the
Check
top corner to the sheet by means of the trough
compass.
• Intermediate checks should be taken wherever
• With the alidade touching ‘a’ sight ‘B’ and draw a ray. possible. If ‘A’ is visible from C, the work done, up to
‘C’ can be checked by sighting ‘A’ with the alidade
touching ‘C’ and noting if the edge touches ‘a’ similarly
other check lines DB, EC etc can be used to the check
the work.
• When no other stations are visible from the station
occupied, take some well-defined object such as
corner of a building which has been previously fixed
on the sheet and it should be used to check the work.

60 Construction: Draughtsman Civil - (NSQF): Related Theory for Exercise 2.3.51 - 52

Resection method of plane table survey
Objective : At the end of this lesson you shall be able to
• state the resection method of plane table survey

Resection Method • With the alidade touching ‘b’ sight the station ‘C’ which
is to be plotted by resection and draw a ray.
• It is used for locating the station points only.
• Estimate the distance BC by judgement only and
• The main feature of resection is that the point plotted move the point ’C’ and along a ray to represent the
on the sheet is the station occupied by the plane table. approximate position of ‘C’
• After stations are fixed the details are taken by • Shift the table and set it up with C, on the ground
radiation or intersection, or sometimes both. point ‘C’.
• Select a base line AB on the ground. • Orient the table by taking back sight on ‘B’ and clamp
it.
• Measure the distance accurately and then plot ‘ab’
in a convenient position. • With the alidade pivoted on ‘a’ sight the station ‘A’
and draw a ray.
• Set up and level the table at ‘B’ so that ‘b’ lies vertically
above B and orient the table by placing the alidade • The point of intersection of this ray and that previously
along ‘ab’ and turning the table till ‘A’ is bisected and drawn from ‘b’ gives the required point ‘C’ (i.e.) true
then clamp it. position of ‘C’.
• It necessary locate the other station in the above
manner. It is also know as back ray method.

Construction: Draughtsman Civil - (NSQF Level 5): Related Theory for Exercise 2.3.51 - 52 61
Construction Related Theory for Exercise 2.4.53 & 2.4.54
Draughtsman Civil - Levelling and contouring
Principle of levelling - Auto level - Dumpy level- Tilting level
Objectives : At the end of this lesson you shall be able to
• describe the principle of levelling
• list the instruments required for levelling
• explain the parts of a level.

Principle of levelling movement of this tubes, telescopes are classified into

two categories such as:
Principle of levelling is to obtain a horizontal line of sight
1 External focusing telescope
from which vertical distances of the points above or below
this line are found. They are achieved with the help of a 2 Internal focusing telescope
level and a levelling staff respectively.
1 External focusing telescope: In this type of
telescope, the body consists of two tubes, one of
Instruments required for levelling
which is capable of sliding axially within the other by
means of rack and pinion arrangements. This action
Two instruments are required for levelling namely
of sliding takes place by operating a focusing screw
1 a level and available in the telescope. As one of this tube moves
out of the other and the length gets altered, the
2 a levelling staff telescope is known as external focusing telescope.

1 The level 2 Internal focussing telescope: In this type of

telescope, out of two tubes on slides into the other,
Level is an instrument used for furnishing a horizontal the outer tube is fitted with both the eyepiece and
line of sight. The essential part of a levelling instrument object glass at its either end. The other interior tube
are the following. carries a double concave lens, which moves inside
to and fro between the diaphragm and the object
1 Levelling head glass. As the movement of inner tube is within the
outer one and the length remains same, the telescope
2 Limb plate is known as internal focusing telescope.
3 Telescope 3 Bubble Tube: A bubble tube consists of a sealed
4 Bubble tube curved glass tube set in a brass tube with plaster of
paris. It is nearly filled with alcohol or either or a
5 Tripod stand mixture of two, and the remaining space is occupied
by air bubble. The tube is graduated on both the
1 Levelling head: A levelling head consists of a tribrach
directions from its centre, which enables to centre
plate having three arms each carrying a levelling
the bubble by operating the foot screws available in
screw in the ball and socket arrangement. These
the levelling head. One division on graduation is
levelling or foot screws are used to bring the telescope
equals to 2 mm. The bubble tube is attached to the
bubble to the centre of its run. It is also an outer follow
top of the telescope by means of capstan headed
conical socket into which fits the inner solid spindle
nuts, it is also otherwise known as ‘level tube’ and
of the telescope, thus representing its vertical axis.
used for levelling up the instrument. In levelling up
The levelling head has an arrangement to fix the
operation bubble in the bubble tube is brought to the
instrument over the tripod.
centre (highest point) and a line tangential to the
curvature of the tube at that point is known as bubble
2 Limb Plate: A limb plate is the one to which the
line. The bubble line is horizontal when the bubble is
telescope is fixed by means of standards or supports.
in the centre.
The lower portion of the limb plate has a solid spindle
which fits into the hollow socket of the levelling head. 4 Tripod Stand: A tripod stand is the one, which
This spindle freely revolves in the outer socket and supports the instrument when in use. It consists of
locked at the bottom by means of a locking nut. three legs either solid or framed one. These legs are
made of mahogany wood and its lower end is fitted
3 Telescope: A telescope is an essential component
with a pointed steel shoes so that it can be firmly
part, which provides the basic line of sight for making
pressed into the ground. The tripod should be rigid
observations in the levelling operation. Telescope
and if it has any looseness it affects the position of
consists of two tubes, one slides into the other and
instrument. The tripod head, as its top carries external
fitted with lens and a diaphragm having cross hairs.
threads to which internal threads of the instrument is
Depending upon the arrangements made for the
fitted.

69
Types of Levels The Y level is a very delicate instrument. It consists of
many loose and open parts, which are liable to frictional
There are various types of levels, viz. wear. The telescope can be removed from the Y
supports, and reversed end for end. It can also be
1 The dumpy level revolved about its longitudinal axis in the Ys.
2 The wye or Y level 3 The cooke’s reversible level
3 The cooke’s reversible level
The cooke’s level combines good features of both the
4 The cushing’s level dumpy and Y levels. By slackening the stop screw the
5 Tilting level and telescope can be rotated about its longitudinal axis in its
sockets and can also be withdrawn from its sockets and
6 The automatic level replaced and for end. (Fig 3)
1 The dumy level (Fig 1)

4 The cushing’s level

In the case of the crushing’s level, the telescope can

neither be removed from its socket, nor can it be revolved
about its longitudinal axis. However, the eye-piece
The dumpy level is simple, compact, and stable. The (carrying with it the diaphragm) and the object glass are
telescope is rigidly fixed to its supports and, therefore, removable, and can be interchanged to reverse the
can neither be rotated about its longitudinal axis, nor can telescope end for the end, both collars being exactly alike.
it be removed from its supports. It has greater stability of Similarly, the eye-piece end can be rotated in its fitting.
adjustments than the Y level.
5 The Modern (Tilting) Level
2 The Wye or Y level (Fig 2)
In the case of this instrument the telescope has a small
motion about a horizontal axis. It is, therefore, known
as the tilting level. The main peculiarity of this level is
that the vertical axis need not be truly vertical, since the
line of collimation is not perpendicular to it. The line of
collimation, is however, made horizontal for each pointing
of the telescope by means of a tilting screws. It is mainly
designed for precise levelling work. (Fig 4)

6 The automatic level

The automatic level also designated as self aligning level.

The fundamental difference between the self alignment
level and the classic spirit level is that, in the former the
line of sight is no longer levelled manually using a tubular
spirit level but is levelled automatically. Within a certain
tilt range this is achieved by an inclination compensating
device called tilt compensator suspended like a
pendulum and inserted in the path of light rays through
the telescope. (Fig 5)

70 Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.4.53 & 54
 Advantages of using auto level

1 Operational comfort: Measurement is not fatiguing

Control of level which is so try to the eyes, nerves
and hands is eliminated. The automatic level does
not require any protection from the sun.
2 High precision: Mean elevation error on invar staff
graduated to 5mm divisions varies between+ 0.5 to
0.8 mm per km of forward and backward levelling.
3 High speed: Time required for levelling work is about
50% of that required with ordinary level. This is an
advantage where work is to be carried out in a limited
time. Errors due to settlement are thereby eliminated.
4 Freedom for errors: The accuracy of a single
measurement is increased by an erect telescope
image, the levelling rods with erect figures in proper
sequence, freedom from fatigue, the possibility of
forgetting to get the bubble in the centre as well as
simple and quick means of operation.
5 Freedom from external influences: The external
influences like marshy ground, rain, wind, sun, loss
of light due to clouds, magnetic fields, continuous
vibrations, transport vibrations, have no influence of
the levelling work.
6 Range of application: The level can be used on
medium and large sized projects and setting Bench
Marks of the 3rd to 1st order.

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.4.53 & 54 71
Construction Related Theory for Exercise 2.4.61
Draughtsman Civil - Levelling and contouring
Introducing to contouring
Objectives : At the end of this lesson you shall be able to
• define contouring
• explain the terms used in contouring
• narrate the characteristics of contour.

Introduction Scale of the Map

Relief The contour intervals kept inversely proportional to the

scale of the map. Smaller the scale of map, larger the
The topographical map showing the configuration of the contour interval. On the other hand, if the scale of the
earth’s surface by the use of suitable symbols is called map is large, the contour interval should be small.
relief. Contour lines are used for representing relief.
Purpose of Map & Extent of Survey
Contour Line
For small extent of survey and for detailed design work
contour interval should be small. For large extent of
A contour line is an imaginary line of constant elevation
survey, the contour interval shall be large. For the survey
on the ground surface. It may be the line of intersection
of canal, railway, road etc. If the work is very important,
of level surface with good surface.
contour interval should be less and vice versa.
E.g show line of still pond or a lake.
Nature of the ground
Contouring The contour interval generally depends upon the
topography of the terrain. In flat ground contour interval
The process of locating the contour lines on the surface is small so that it will be suitable to depict the general
of the earth or on the plan or map is known as contouring. nature of the ground. Whereas in hilly areas can be
depicted with contours at larger interval.
Contour interval
Availability of time and fund
The vertical distance between two consecutive contours
is called contour interval. It is kept constant for a contour If the time and fund available is less, large contour interval
plan to correctly represent the topography of the terrain. is adopted or vice versa. This is due to the fact that the
greater the interval, the smaller is the amount of field
Horizontal equivalent work, reduction and plotting required in the preparation
of the plan.
The least horizontal distance between two consecutive
contours is called horizontal equivalent. It is different at The contour interval for general topographical may be
different part of the contours and it depends upon the computed by the following rule.
slope of the ground. It is usually less in hills than in plains.

Factors for deciding contour interval

Contour interval on a map is decided on the following

considerations.

Considering the above factors, the contour intervals

recommended for the contour plans for various purposes
are as follows.

94
 S No. Purpose of Survey Scale Contour Interval in Metre

1 Building site 1c m = 10 m or less 0.2 to 0.5

2 Town planning schemes, 1 cm = 50 m to 100 m 0.5 to 2

reservoirs landscape grading

3 Location surveying 1 cm = 50 cm to 200 m 2 to 3

4 For general topographical 1 cm = 100 m or more 3 m & above

work

Uses of contours
Objectives: At the end of this lesson you shall be able to
• explain the uses of contour
• explain the methods of contouring

Uses of contour maps Methods of Contouring

• To study the general character of a tract of land without The method of locating contours may be classified into
visiting the ground if the countour map of the area is two Direct method and indirect method.
available.
Direct Method
• To decide the most economical and suitable site for
engineering works such as canals, sewers, reservoirs,
In this method, the contours to be located are directly
roads, railway etc.
traced out in the field with a level or hand level by marking
• To determine the capacity of the reservoirs and the various points along a contour. These points are then
catchment area of a drainage basins. surveyed and whose positions are plotted. The line joining
these points gives the required contour.
• To compute quantity of earth work required for filling
or cutting along the proposed alignment of the project
This method is very slow and tedious , but it gives very
such as canals, roads etc.
accurate results. It is used for small areas and for works
• To ascertain the invisibility of points. of high precision.
• To trace gradient for the road alignment.
In this method, first a temporary BM is established in the
• To draw longitudinal section and cross section to area where contouring is to be done by running fly levels
ascertain the nature of the ground in any desired from a permanent BM. Then the level is set up at a
direction. position from where maximum area can be visible. For a
BS reading is taken on the BM. From that calculate the
• To decide the best positions for the guns, the line of
height of instrument. To locate the points along a
march and campaining grounds by the army
particular contour, required staff reading is calculated by
commanders during wars.
subtracting the reduced level from the height of
instrument.
Locating Contours
Then contour points are located by moving the staff up
The location of contour on a map can be plotted only
and down along the slope until the desired staff reading
after knowing the horizontal position and vertical elevation
is obtained. The points are surveyed and whose positions
of the points consisting of the contours. The fixing of the
are plotted on the plan.
horizontal position of the points is known as horizontal
control and it depends upon the size, shape and
Direct method by radial line
importance of work. It may be carried out either by chain
survey or compass survey or plane table survey. For
In this method, contour points are located along the radial
small areas, chain survey is adopted and for large areas
lines from a common point at the centre.
traversing is adopted.
Select a point at the centre of the area to be surveyed so
The fixing of the vertical height of points is known as
that all the points can be commanded from that point
vertical control and it is carried out by the process of
and their relative positions are fixed by measuring the
levelling.

Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.4.61 95
horizontal angles or bearing. Place the levelling Hold the staff vertically and move up and down along
instrument over the selected point and find the height of these radial lines until desired staff readings for their
instrument with reference to the temporary BM respective contours are obtained. The positions of these
established on the contour site. Calculate the staff points obtained are located by measuring their distances
readings required, to locate the points along various from centre point. Join the points of same elevations to
contours of different reduced levels. get the required contours.

96 Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.4.61
Construction Related Theory for Exercise 2.5.69
Draughtsman Civil - Theodolite
Introduction to theodolite
Objectives: At the end of this lesson you shall be able to
• explain the uses of theodolite
• explain the classify theodolite
• explain the designate theodolite.

Introduction A theodolite is said to be non-transit one if its telescope

cannot ne revolved through 1800 in a vertical plane about
Theodolite is primarily used for measuring horizontal and its horizontal axis. Non transit theodolities are obsolete
vertical angles. It was invented by Roemer, a Danish nowadays
astronomer in 1690. The instrument was used to observe
astronomical observations. Later it was modified to suit Designation of theodolite
the surveying requirements. It is primarily used for
measuring horizontal angels. Later further aditions were The size of a theodolite is defined by its diameter of the
made to make possible of several uses such as graduated circle of the lower plate. For example, a 25cm
prolonging a line, establishing line, levelling, measuring theodolte means the diameter of the lower graduated
the distance indirectly (tacheometry) etc. circle is 25cm.

It is sometimes referred to as universal instrument.

Theodolite is very useful instrument for engineers.

Classification of theodolite

Theodolites may be classified into the following two types.

1 Transit or engineer’s theodolite and

2 Non – transit theodolite.

A theodolite is said to be transit one when its telescope

can be revolved through 1800 in a vertical plane about
its horizontal axis, thus turning the telescope in exactly
opposite direction. All modern theodolites are transit type.

111
Types of doors - I
Objectives: At the end of this lesson you shall be able to
• define doors & windows
• explain the features & location of doors & windows
• enlist the technical terms
• determine size of doors
• explain door frame
• enumerate types and classifications of doors
• explain types of doors according to arrangement of components Introduction.

A door or window is an unavoidable part of building, which The frame is secured to the wall opening with the help of
may be a frame work of wood, steel, glass to give access hold fasts. And window shutters are held in position by
to men, materials, light and ventilation. the window frame.

Definition Location of doors and windows

Door may be defined as an openable barrier secured in The following points should be kept in mind while locating
a wall opening. A door is provided to give an access to doors and windows.
the inside of a room of a building.
1 The number of doors in a room should be kept
Basically a door consists of two parts: minimum since large number of doors causes
obstruction and consume more area in circulation.
1 Door frame and
2 The location of door should meet functional
2 Door shutter. requirements of a room. It should not be located in
the centre of the length of a wall. A door should
The door shutter is held in position by the door frame preferably be located near the corner of a room, nearly
which in turn is fixed in the opening of the wall by means 20cm away from the corner.
of hold fasts.
3 If there are two doors in a room, then they should
A window is also a vented barrier secured in a wall preferably be located in opposite walls facing each
opening. The function of the window is to admit light and other, so as to provide good ventilation and free air
air to the inside of building and to give a view to the circulation in the room.
outside. 4 The size and number of windows should be decided
on the basis of important factors, such a distribution
A window also consists of two parts: of light control of ventilation and privacy of occupants.

1 Window Frame. 5 The location of a window should also meet the

functional requirements of the room such as interior
2 Window shutter. decoration, arrangement of furniture etc.
6 A window should be located in opposite walls, facing
door or another window, so that cross ventilation is
achieved.
7 From the point of a view of fresh air, a window should
be located on the northern side of a room or located
in the prevalent direction of wind.
8 The Sill of a window should be located about 70cm-
80cm above floor level of the room.

164 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.6.78
 Technical terms

Sl No. Terms Figure

1 Frame: It is an assembly of
horizontal and vertical members
forming an enclosure to which the
shutters are fixed.
2 Shutters: Openable part of a door
or window.
3 Head: Topmost horizontal part of a
frame.
4 Sill: Lowermost horizontal part of a
frame.
5 Horn: Horizontal projection of head
or sill.
6 Style: Vertical outside member of the
shutter frame.
7 Top rail: Top most horizontal
member of a shutter.
8 Lock rail: Middle horizontal member
of door a shutter.
9 Bottom rail: Lower most horizontal
member of a shutter.
10 Cross rail: Additional horizontal rails,
fixed between the top and bottom
rails of a shutter.
11 Panel: Area of shutter enclosed
between the adjacent rail and styles.
12 Mullion: Vertical member of a
frame, which is employed to sub-
divide a window or a door.
13 Transom: Horizontal member of a
frame which is employed to sub-
divide a window opening horizontally.
14 Hold fast: Mild steel flats, generally
bent into Z-shape, to fix or hold the
frame to the opening.

Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.78 165
 Sl No. Terms Figure
15 Rebate: Depression or recess made
inside the door frame, to receive the
door shutter.
16 Sash: Special type of frame, made
of light sections and designed to carry
glass.
17 Louvers: A piece of timber which is
fixed is in inclined position within a
frame.
18 Architrave: A strip of wood, usually
moulded or splayed which is fixed
around the sides and head of
opening

Size of Doors c 1.20m x 2.25m

Indian standard Instituion recommends that the size of
The size of door should be such that it would allow the
door frame should be derived after allowing a margin of
movement of largest object and tallest person likely to
5mm all round an opening for convenience of fixing. The
use. As a rule, the height of door should not be less than
width and height of an opening is in directed by no.of
1.80M. The width of door should be such that two
modules where each modules is of 100mm.
persons can pass through it walking shoulder to shoulder.
The common widths – height relation used in india is as
For example a designation of 8 DS 20 denotes a door
follows.
opening having width equal to 8 modules (is 8x 100=800
mm) and height=20 modules (is 20 x 100 = 2000 mm)
1 Width = 0.40 to .0.60 height
with single shutter.
2 Height= (width +1.2) metre.
The letter ‘D’ denotes a door opening and letter‘s’ stands
The following are the generally adopted sizes of doors for single shutter. Illrly the designation 10DT 21 of door
for various types of buildings. opening denotes.

I Doors of residential building. Width of opening = 10 x 100 = 1000 mm

a External door = 1.00 x 2.00m to 1.10 x 2.00m Height of opening = 21 x 100 = 2100 mm
b Internal door = 0.90 x 2.00m to 1.00 x 2.00 m
D - Stands for door, T-stands for double shutter. The
c Doors of bathrooms and closets thickness of shutter shall be 20,25 or 30 mm depending
= 0.70 x 2.00 to 0.8 x 2.00m upon size.

d Carriage of cars Door frame

= 2.25m (height) x 2.25m width
to 2.25m (height) x 2.40 width A door frame is an assembly of horizontal and vertical
members forming an enclosure to which door shutters
II Public building such as schools, hospitals, libraries, are fixed. The vertical members are known as jambs,
etc. posts, while the horizontal top member connecting the
a 1.2m x 2.00m posts is called the head which has horns on both sides.
The size of the frame is determined by allowing a
b 1.2m x 2.10m
clearance of 5 mm to both the sides and top of an opening
166 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.6.78
Door frame are made of following matrials. Out of these, timber frames are more commonly used.
However in factories, workshops etc steel frames are
1 Timber used. Aluminium frames are costlier and are used only
2 Steel Section. for residential buildings where more funds are available.
With the increasing cost of timber, concrete frames are
3 Aluminum section. more popular in urban areas.
4 Concrete.
5 Stone.

Classifications
According to arrangement On the basis of method On the basis of working Metal doors
of components of manner of Construction operation
Battened and ledged doors Framed and paralled Revovling door Mild steel door
door
Battened ledged and braced Glazed or sash door Sliding door Corrugated steel
doors door
Battened ledged and framed Flush door Swing door Hollow metal door
Battened ledged, braced Louvered doors Collapsible door Metal covered
and framed doors plywood door

Wire gauged doors Rolling steel shutter door

Battened and ledged doors (Fig 4) Battened ledged and braced doors (Fig 5)

This is the simplest type doors, specially suitable for These doors are similar to ledged doors except that
narrow opening when strength and appearance are not diagonal members known as braces are provided as
important. These doors are formed of vertical boards shown in figure. The braces are generally 10cm – 15
known as battens which are usually tongued and grooved cm wide and 30 mm thick. The brace give rigidity to the
and are fixed together by horizontal supports known as door and hence doors of this types are useful for wide
ledges. Batterns are 10-15cm wide and 20mm-30mm opening. It should be noted that braces must slope
thick. Ledges are generally provided at the top, middle upwards from the hanging side as they have to work in
and bottom. The door is hung to the frame by means of compression and not in tension.
T-Hinge of iron.

Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.78 167
Battened ledged and framed doors Battened ledged framed and braced doors

In this type of doors a frame work for shutters are This is just similar to the battened ledged and framed
provided to make the door stronger and better in doors, except that brace are introduced. This type of door
appearance as shown in figure. Styles are generally 10cm is durable and stronger and hence it can be used for
wide and 40mm thick. The ledges are provided as usual. external use. The brace must stop upward from hanging
The total thickness of styles is made equal to the side.
thickness of ledges & thickness of batterns.

Types of doors - II
Objectives: At the end of this lesson you shall be able to
• explain types of door according to manner of construction (framed and panelled door, glazed or sash door)
• explain types of door according to manner of construction (flush door, louvered door and wire gauged door)

Framed and panelled door (Fig 1) Features of framed and panelled door

The styles are made continuous from top to bottom that

is they are in single pieces.

Various rail (in top rail, bottom rail and intermediate rail)
are jointed to the styles at both the ends.

The styles and rails are jointed by tenon and mortised

joints.

The bottom and lock rail are made wider than top and
frieze rails.

The entire frame is grooved on all the inside face to

receive panels.

Additional timber beading is provided on one or both the

sides to improve the elevation of the door.

The minimum width of the style is kept as 100mm. The

minimum width of bottom rail and top rail is kept as
150mm.
These type of doors are widely used in almost all types
of buildings since they are strong and give better If panels are made timbers, its minimum width should
appearance than battened doors. This door consists, of be 150mm and minimum thickness should be 20mm.
frame-work in the form of vertical members called styles
and horizontal member called rails which are grooved However the maximum area of single panel of timber
along the inner edge of the frame to receive the panels. should not be more than 0.5m2. These districtions do
The panels are made from timber, plywood, block boards, not apply to panel of plywood, particles boards on hard
A.C sheet or even glasses. Panalled doors are of various board.
types such as.
Glazed or sash door (Fig 2)
Single panelled doors
Glazed or sash door are provided where additional light
Two panelled doors is required to be admitted to the room through the door
or where the visibility of the interior of the room is required
Three panelled doors from the adjacent room. Such doors are commonly used
in residential as well as public buildings like hospitals,
Multiple panelled doors schools colleges etc. The doors may be within fully
glazed or they may be partially glazed and partially
Panelled doors may contain single leaf for small opening paneled. In the letter case the ratio of glazed portion to
or may contain two leaves for wider openings. In double the paralled portion is kept 2:1 is bottom 1/3rd height is
leaf door each leaf has separate frames each hinged to paralled and top 2/3 height is glazed. The glass is
the corresponding jamb post of the door. required into the rebate provided in the wooden sash
bars and secured by rails and putty. Partially glazed doors

168 Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.78
are sometimes provided with styles which gradually get grains of core at right angles to that of the cross bands.
diminished at lock rail to improve the elevation or to Such doors are quiet strong but are heavy and require
permit more area for the glazed panels. Such style which more materials.
decrease in width at lock level are called diminishing
style or gun stock rail or gun stock style.

Flush Door

Flush doors are becoming popular these days because

of their pleasing appearance, simplicity of construction,
less cost, and greater durability. They are used both for
residential as well as public and commercial buildings.
These doors consist of solid or semi-solid skeleton or
core covered both sides with plywood, or veneers etc.
This door presents a flush and joint less surface which
can be neatly polished.

Flush dooors are of two types

a Solid core or laminated core flush door

b Hollow core or celluar core flush door (framed)

a Solid core or laminated core flush door

(Fig 3 & 4)

Solid core flush door consists of framework in the form

of styles, top and bottom rails of not less than 75 mm
width. The inner space of the frame is provided with block b Hollow or cellular core flush door (Framed flush
board or particle board. door) (Fig 5)

In the laminated core flush door the wooden strips of A hollow core flush door consists of frame made up of
maximum width 25mm are glued together and length of styles, top and bottom rails and a minimum of two
each strip is equal to the length of the laminated core. It intermediate rails, each of minimum 75 mm width. The
is housed in the outer frame made of styles, top and inner spaces of the frame is provided with equally spaced
bottom rails of not less than 75 mm width. battens each of minimum 25 mm width, such that the
area of voids is limited to 500 cm2.
In each type of core, plywood sheets are glued under
pressure to the assembly of core housed in the frame A cellular core flush door consists of frame work made
on both faces. Alternatively separate cross bands and of style, top and bottom rails each of 75 mm width. The
face veneers can be glued on both the faces, with the
Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.6.78 169
voids space is filled with equally spaced battens of wood Louvered doors permit free circulation of air through them
or plywood, each of minimum 25mm width. The battens and at the same time maintain the privacy of the room.
are so arranged that the voids space between the However these doors catch dust which is very difficult to
adjacent vertical and horizontal batterns does not exceed be cleaned. These doors are generally used for latrine
25 cm2 in area. Total area of voids does not exceed 40% and bathrooms of residential and public buildings. The
of the area of the shutter. doors may be either louvered to its full height or it may
be partially louvered and partially. Panelled. The louverds
are arranged and partially paneled. The louvers are
arranged at such an inclination that vision is obstructed
while they permit free passage of air. This is achieved
by fixing the upper back edge of a louver, higher than
the lower front edge of the louver just above it. Louvers
may be either movable or fixed. In the case of movable
louvers, a vertical piece of timber is provided to which
louvers are attached through hinges. The movement of
louver is activated by the vertical piece of timber. Louvers
may be made of either timber or glass or plywood.

Wire gauged doors (Fig 7)

In both types, shutters are formed with, plywood sheets

or cross bands and face veneers which are glued under
pressure to both the faces of core.

Louvred or Venetian Door (Fig 6)

These types of doors are provided to check the entry of

flies, mosquitoes, insects etc. Wire mesh is provided in
the panels and therefore they permit free passage of air.
Such doors are commonly used for refreshment room,
hotels, cup-boards containing estables in sweet shops
etc. The door is formed of wooden framework consisting
of vertical styles and horizontal rails and the panel
opening are provided with fine mesh of galvanized wire
gauges. The wire gauge is fixed by means of nails and
timber beadings. Generally the door has two shutter is
fully panelled and the outer shutter has wire gauged
panels.

170 Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.78
Types of doors - III
Objectives: At the end of this lesson you shall be able to
• explain types of doors according to working operation.

1 Revolving Doors (Fig 1) In this type of door, the shutter slides on the side with
help of runner and guide rails. The shutter may be of
one or several leaves and can slide either on one side or
both the sides. Cavities may be provided in the wall to
receive the door in an open position or it may be simply
lie touching the wall. As sliding door does not cause any
obstruction during movement, it is used for entrance of
godowns, sheds, shops, show rooms etc. It is provided
with handles, locking arrangement, stopper etc.

Swing Door (Fig 3)

Such doors are provided only in public buildings such as

libraries, museums, and banks etc. where there are
contant visitors. Such doors provide entrance to one
person and exit another person simultaneously and close
automatically when not in use. This door is also suitable
for air conditioned buildings and buildings at places where
strong breeze blow throughout the year, since the door
is so assembled that it excludes the wind drought. The
door many consist of centrally placed mullion to which
four radiating shutters are provided. The mullion or
vertical timber is supported on ball bearings at the bottom
and has bush bearing at the top so that it rotation is A swing door has its shutter attached to the door frames
without any jerk, friction and noise. The shutters may be by means of special double action spring hinges so that
fully glazed, fully paneled or partially glazed and partially the shutter moves both inward and outward as desired.
parelled. The shutters and the mullion are enclosed in a Generally such doors have single leaf, but two leaves
vestibule. Vertical rubber piece are provided at the can also be provided. Such doors are not rebated at the
rubbing ends of shutters to prevent draught of air. The meeting styles. The closing edge of which should be
radiating shutter can be folded when traffic is more. The segmental when the door is to be used, a sight push is
opening can also be closed. made and the action of spring brings the shutter to closed
position. The return of the shutter is with force and hence
Sliding Door (Fig 2) in order to avoid the accident, either the door should be
fully glazed or a peep hole should be provided at the
eyelevel as shown in figure 3.

Collapsible Steel Door (Fig 4)

A collapsible door may consist of a mild steel frame. Two

vertical pieces of mild steel channels about 15 to 20 mm
wide are jointed together with the hollow portion of the
channel insides; so that a vertical gap is created. Such
channel units are spaced at 100-120 mm apart and are
braced with flat iron diagonals 10-20mm wide and 5 mm
thick. These diagonals allow the shutter to open out or
get closed. The door can be opened or closed by a slight
push or pull. A collapsible door thus work without hinges.
It is used for compound gate, residential building, sheds,
godown etc.

Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.78 171
 A rolling steel shutter may consist of a frame, a drum
and a shutter of thin steel plate or iron sheet of thickness
about 1mm. Grooves of about 25 mm thickness are left
in the frame. A horizontal shaft and springs are provided
in the drum at the top. The diameter of drum is about 20
cm – 30 cm. The shutters are usually rolled in turns.
Thus a slight push or pull will open or closed the shutter.

Rolling steel shutter doors are sufficiently strong and they

can be easily rolled up or down. They cause no
obstruction to the floor as well as openings. Rolled steel
shutter door are usually provided for garages,
showrooms, shops, godowns etc. They provide security
against fire, but the appearance is not good. They cause
noise in movement.

Rolling Shutters are two types:

i Pull push type rolling shutters provided for door

opening area less than 10m2
ii Mechnical gear type rolling shutters provide for door
opening are greater than 10 m2

Rolling Steel Shutter (Fig 5)

172 Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.78
Construction Related Theory for Exercise 2.6.79 & 2.6.80
Draughtsman Civil - Carpentry joints

Windows and ventilators

Objectives: At the end of this lesson you shall be able to
• enumerate factors for selection of size, location & no. of windows in a room
• describe Indian standard recommendations of windows
• explain different types of windows and ventilators.

Introduction Based on these factors the following thumb rules are in

use.
Windows: Windows are necessary for ventilation and
lighting. These are usually glazed with clear or opaque 1 Breath of window = 1/8 (Width of room + Height of
glasses. As already stated, not less than 10 t0 15 percent room)
of the floor area of a room is given to windows opening
2 The total area of window opening normally varies from
to the outside. The smaller the floor area, the larger will
10-12% of the floor areas of the room depending upon
be the percentage.
the climatic conditions.
Ventilators 3 The area of window opening should be at least 1 sq.m
for every 30-40 cubic metre of the room volume.
Ventilators are windows of small heights and they are
4 In public buildings, the minimum area of window
fixed at the top of door or window. The ventilators are
should be 20% of floor areas.
provided with glass panels and steel grill is fixed in
ventilator for the purpose of safety. 5 For sufficient natural light, the area of the glazed panels
should at least be 8-10% of the floor area.
Windows
Indian standard recommends that the size of window
The selection of size, shape location and no. of windows frame. Should be derived after allowing a margin of 5
in a room depends upon the following factors. mm all round an opening for convenience of fixing. The
width and height of an opening is indicated by a number
1 Size of the room of modules, where each module is of 100 mm. A
2 Location of the room designation 6ws 12 indicates a window opening with
single shutter having width equal to 6 modules.
3 Utility of the room
4 Direction of the wall It, 6 x 100 = 600 mm
5 Direction of the wind And height equal to 12 modules
6 Climatic conditions such as humidity, temperature etc.
It, 12 X 100 = 1200 mm
7 Requirement of exterior view
8 Architectural treatment to the exterior of the building. Indian standard recommendations for size of opening
size of frame and size of window shutters are given
below:

Sl No Designation Size of Opening Size of Window frame Size of window shutters

1 6 WS 12 600 x 1200 590 x 1190 560 x 110

2 10 WT 12 1000 x 1200 990 x1190 460 x 1100
3 12 WT 12 1200 x 1200 1190 x 1190 560 x 1100
4 6 WS 13 600 x 1300 590 x 1290 560 x 1200
5 10 WT 13 1000 x 1300 990 x 1290 460 x 1200
6 12 WT 13 1200 x 1300 1190 x 1290 560 x 1200

173
Types of Windows

The Common Verities of windows used in building

construction are as follows:

1 Fixed Window
2 Pivoted window
3 Double hung window
4 Casement window
5 Sliding window
6 Sash window
7 Louvered window
8 Metal window
9 Bay window
10 Clerestorey window
11 Dormer window
12 Corner window
13 Gable window
14 lantern window
15 Sky lights
16 Ventilators
17 Combined windows and Ventilators.

Fixed Window (Fig 1)

These windows are provided for the only purpose of

admitting light and providing vision in the room. This
window may consist of a window frame to which shutters
are fixed. No rebate are provided to the window frame.
The shutters are fully glazed.

Pivoted window (Fig 1)

In this type of window the shutter is capable of rotating

about a pivot fixed to window frame. The window frame
has no rebate. The shutter can rotate horizontally or
vertically depending upon the position of pivot.

Double – hung window (Fig 2)

This type of window consist of a pair of shutters arranged

Casement window (Fig 3)
one above the other which can slide vertically within the
grooves provided in the frame. A pair of metal weights
Window where shutters open like door are called
connected by chain passing over pulleys, is provided for
casement windows. The window has a frame which is
each shutter. By this arrangement the window can be
rebated to receiving the shutters. The shutters consist
opened at top or bottom to the desired extent by pulling
of style, top rail, bottom rail and intermediate rail, thus
the metal weight suitably. Thus in this type of window, it
dividing it into panels. The panel may be glazed or
is possible to have controlled ventilation. In addition,
unglazed or partially unglazed. In case of windows with
the shutter can also be cleaned easily. double shutters, the outer shutter may have wire-gauged
panels.

174 Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.79 & 80
Sliding Window Steel window can be fixed direct in the masonry opening
in the wall or it may be fitted in a wooden frame fixed in
In this type of window the shutters move on roller and a window opening in the wall. It should be ensured that
can slide horizontally or vertically similar to slding door. no load of the wall etc, is transferred to the window frame.
For this it is usual practice to keep the size of the window
Sash or glazed window opening slightly more than that of window frame. Also
the frame may be fixed in the opening after the masonry
In this case the window shutter consists two vertical work is complete.
styles, top and bottom rails. The panel space of window
shutter between the style and rail is fixing divided by sash Method of fixing metal windows (Steel windows)
bars into panels of small size for fixing glass panels. The
glass panels are secured in position either by putty or by The prepared opening in which steel window frame is to
fillets, known as glazing beads. be fixed is cleaned and exact position of the window
frame is maked by drawing lines.
Louvered window (Venetian window) (Fig 4)
The distance of fixing holes on the frame are measured
In this type of windows the lowers are provided as in the and these positions are marked on the chalk line drawn
case of louvered doors. They allow free passage or air in the opening.
when close and at the same time they maintain sufficient
privacy. The shutter consists of top rail, bottom rail and Holes are cut in brick masonry of size 5 m2 and 5-10cm
two styles; which are grooved to receive the louvers. The deep to accommodate hold fast or legs. In case of stone
economical angle of inclination of the louvers is 450 and masonry or R.C.C work where it is difficult to cut holes
they are generally fixed in position. for legs, wooden plugs are embedded at appropriate
places during the construction itself. The window frame
Metal window is then fixed to these plugs with the help of galvanized
iron or wood screws.
These are now a day’s widely used especially in public
buildings. Windows are made of metals like mild steel, The frame is placed in the opening and position is
glavanised mild steel, aluminimum, bronze, stainless adjusted in correct alignment by striking wooden wedges
steel etc. Bronze, aluminium and stainless steel are in correct position. Since there is a little gap between the
considered to be the best as they process high degree opening and window frame temporary wooden wedges
of elegance, finishing, durability and are dust-proof as can be easily driven after adjusting the window in correct
well. Mild steel being cheapest of the above metals, steel alignment the legs are screwed light in the frame.
window works out to be the most economical. Hence
steel windows are extensively used in all types of Legs are grouted into the holes with cement mortar. After
buildings. grout has set, wooden wedges are removed and space

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.6.79 & 80 175
between the opening and frame is filled with cement
mortar.

Following precaution is to be taken in metal

windows:

The members of the frame and sash should be properly

welded at corners.

Precaution should be taken to prevent the corrosion of

metal windows. Clere – storey window (Fig 6)

Glasses panels should be properly fixed. These windows are provided near the top of main roof.
The pivoted windows are used for this purpose. The
The metal frame should be embedded in cement or clere-storey windows provide ventilation to the inside of
bituminous mastic to prevent the entry of moisture on the room where the front is blocked by veranda and
rain water. improved the appearance of the building.

It is advisable to check and slightly adjust the movement

of shutter before erecting the window in the opening.

The handles to the window should be fixed before doing

the glazing work.

Scaffolding members or any other support should not

be tilt down the metal windows. Otherwise the window
will be damaged.

The masonry opening to receive the metal window should

be prepared in proper level and plumb.

Following are the advantages of steel windows over

wooden windows

The steel windows are factory made products and hence

they possess greater precision as compared to the
wooden windows.

The steel windows are not subjected to contraction and

expansion due to whether effects as sin the case of
wooden windows.

The steel windows exhibit elegant appearance. Dormer Window (Fig 7)

The members of steel windows are narrow and hence

the steel windows admit more light and ventilation for
the same area as compared to the wooden windows.

The steel windows are highly termite proof and fire proof.

Steel windows are more durable and stronger as

compared to wooden windows.

Bay windows (Fig 5)

Bay windows project outside the external walls of a room.

This projection may be triangular, circular, rectangular
or polygonal in plan. Such a window is provided to get
an increased area of opening for admitting more light
and air. They also provide extra space in the room, and A dormer window is a vertical window built in the sloping
improved the overall appearance of the building. side of the pitched roof. This window is provided to
achieve proper ventilation and lighting of the enclosed

176 Construction: Draughtsman Civil - (NSQFLevel -5): Related Theory for Exercise 2.6.79 & 80
spaces below the roof. Dormer window also serves as These are the windows which are fixed on flat roofs to
an architectural feature of the building. provide light to the inner portion of the building where
light coming from the windows in external wall is in
Gable Window (Fig 7) sufficient. They may be square or rectangular or curved.
Glass panels are generally fixed; but if ventilation is
The windows provided a in the gable end of a pitched required in addition to light, then pivot window may be
roof are known as a gable windows. provided.

Corner window (Fig 8) Sky light (Fig 10)

A sky light is provided on a sloping roof to admit light.

The window project above the sloping surface and is
parallel to the sloping roof surface. The sky light is
provided with a view to permit the room below to be fully
lighted with natural light. The opening for sky light is made
These windows are provided at the corner of the room by cutting the common rafters.
and thus they have two faces and two directions. Due to
this there is entry of light and air from two directions and Ventilators
in many cases the elevation of the building is also
improved. However special lintel will have to be casted Ventilators are small windows fixed at a greater height
at the corner and jamb posts of the window at the corner than the window, generally about 30-50cm below the roof
will have to be made of heavy section. level. The ventilator has a frame and a shutter generally
glazed and horizontally pivoted. The top edge of the
Lantern Window (Fig 9) shutter open inside the bottom edge open outside so
that rain water is excluded.

Ventilators combined with window or door

Ventilators may be provided in continuation of a door or

a window at its top. Such a ventilator is known as Fan-
light. The construction of a fan light is similar to sash
window. Such a ventilator is usually hinged at top and
can open out. Alternatively, the ventilator shutter can he
hinged at the bottom.

Construction: Draughtsman Civil - (NSQF Level -5): Related Theory for Exercise 2.6.79 & 80 177
Stairs
Objectives : At the end of this lesson, you shall be able to,
• define stair, stair case
• enlist the technical terms
• define the different types of slip.

Introduction

A stair is a convenient means of access between the floors

of a building. It is constructed to provide ready, easy,
comfortable and safe ascent/descent with series of steps
that are neither laborious nor difficult to climb within an
enclosure called stairwell (Staircase).

Definition

A stair is defined as a series of steps suitably arranged

for the purpose of connecting different floors of a build-
ing. It is provided to afford the means of ascending and
descending between floors and landing. The room or
enclosure of a building in which the stair is located is
known as stair case. The opening or space occupied by
the stair is known as stair way. It should be suitably lo-
cated to provide easy access to all the rooms.

The definitions of technical terms used in connection with

the stair are:-

Sl.No Terms Definition

1. Tread The horizontal upper portion of step

2. Going Horizontal distance between faces of two consecutive risers.

3. Riser The vertical front member of step

4. Rise Vertical distance between two successive treads

5. Flight Series of step between landings

6. Nosing The projecting part of the tread beyond the face of riser

7. Scotia Additional moulding provided under the nosing to improve the elevation of step and to
provide extra strength to nosing end

8. Walking Line The approximate line of movement of people on a stair. It may be 45 cm from the
centre of handrail.

9. Head room The vertical distance between the nosing of one flight and the bottom of the flight
immediately above.

232 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.9.85
10. Run Total length of stair in a horizontal plane. It includes the lengths of landings also.

11 Soffit The under surface of stair

12 Waist The thickness if structural slab in case of RCC stair

13 Stringers Inclined member in wooden stairs acting as wooden beams to support the steps.

14 String The inclined member of a stair which supports the ends of step is known as string.

a Cut or In the cut or open string, the upper edge is cut away to receives the ends of steps as
open string. shown in fig 3.

b A closed In the closed or housed string, the ends of steps are housed between straight parallel
or housed edges of the string as shown in fig 3.
string.

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.9.85 233
 15 Pitch The angle of inclination of stair with the floor.

16 Landing Horizontal platform between two flights to change of direction and to take rest for users.

17 Baluster The vertical member fixed between string and hand rail to give support to hand rail

18 Handrail The inclined rail over the string

19 Newel post Vertical member placed at the end of flights to connect the ends of string and handrail.

20 Balustrade The combined frame work of hand rail and baluster.

or Barrister

STEPS: It is a portion of stairs which permits ascent or decent it comprises of a tread and riser. A stair is composed
of a set of steps.

Types of steps (Fig 4)

Sl. no Terms Definition

1 Flier Ordinary step of rectangular shape in plan

2 Bull nose step It forms a circular quadrant in plan and provided at the bottom of flight

3 Commode step This step has a curved rise and tread

4 Dancing step Step do not radiate from common centre

5 Round ended step Similar to bull nose step except that its ends are semicircular in plan

6 Splayed step One end or both ends splayed in plan.

7 Winder Tapering step and used to change the direction of flight

234 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.9.85
Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.9.85 235
Construction Related Theory for Exercise 2.9.86
Draughtsman Civil - Vertical movement

Classification of stairs according to shape

Objectives : At the end of this lesson, you shall be able to
• classify the means of vertical transportation
• explain types of stairs according to shape.

Means of transportation between the floor

Ramp Ladder Stair Escalator Lift

According to materials used According to shape

Brick Wooden Stone Metal R.C.C Straight Turning Circular Geometrical

stair stair stair stair stair stair stair or Spiral stair
stair

Quater Half turn Three quarter

stair stair stair

Bifurcated
stair
Dog- legged Open newel
stair stair

Stair

Types of stairs

Stairs are classified as follows.

A Straight stair
B Turning stair
C Circular or spiral stair
D Geometrical stair B Turning stair : In case of turning stair the flights takes
turn.
A Straight stair : In case of straight stair all steps leads The usual type of turning stair are described below.
in one direction only. This type of stair may consist of one
or more flights and they are used when space available 1 Quarter-turn stair
for staircase is long but narrow in shape. (Fig 1)

236
C Circular helical or spiral stair (Fig 7) D Geometric Stair (Fig 8)

These stairs have any geometrical shape and they do

not require newel post. The handrail of a geometrical stair
continuous without interruption and without any angular
turns. Considerable skill is required for the construction
of a geometrical stair and it is found that a geometrical
In this type of stair, the steps are radiate from the centre. stair is weaker than corresponding open-newel stair.
The flights consist of winders only and they may be con-
tinued through any desired number of turns. Spiral stair
may be constructed of cast-Iron, Mild steel, concrete.
Usually the structural design and construction of spiral
stair are complicated in nature. For concrete spiral stair,
steel reinforcement is heavy and framework is compli-
cated so it is expensive. Spiral stair is useful where space
available is limited and where traffic is less.

Classifications stair according to material and requirements of good stair

Objectives : At the end of this lesson, you shall be able to,
• classify the stair according to materials
• explain the requirements of a good stairs
• design the stair case as per the given data.

Introduction Stone Stair

Any well planned stair should meet the following criteria The stone to be used for the construction of stair should
for easy, quick and safe ascent/decent. be hard, non-absorbent and they should possess enough
resistance to the action of fire. These stairs are used for
Classification of stair according to materials used ware houses, work shopes etc.

Following are the materials which are commonly used in Construction

the construction of a stair
A stone step may be constructed in any one of the follow-
1 Stone stair ing ways.
2 Wooden stair
a Rectangular step (Fig 1)
3 Brick stair
4 Metal stair In case of a rectangular step the arrangement is made of
as shown in figure. The overlap is about 25 mm to 40
5 R.C.C stair
mm. This arrangement results in considerable saving in
labour of cutting and dressing stone.

238 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.9.86
Construction Related Theory for Exercise 2.10.88
Draughtsman Civil - Roof & roof covering

Roofs
Objectives : At the end of this lesson, you shall be able to
• define Roof
• identify the components of roof
• classify the roof
• forms of pitched roof
• explain the pitched roof.

Introduction Span: Horizontal distance between internal faces of wall

Roof is the uppermost part of the building, which is sup- Rise: The vertical distance between top of ridge piece
ported on structural members and covered with a roofing and wall plate
material. Basically roof consists of trusses, portals,
beams, slabs, and domes. The roof covering may be AC Ridge: Wooden member provided in ridge line
sheet, G I sheet, Wooden shingles, tiles etc.
Rafters: Members which support extend from eaves to
Definition ridge

A topmost covered structure provided over a building to Common Rafter : Rafter which supports roofs covering
protect from rain, snow, sun, and wind is called Roof. and extend from eaves to ridge

Elements of roof (Figs 1 & 2) Principal rafter: Rafter which supports purlins

Jack rafter: Rafters shorter than common rafter

Hip rafter: Rafter provided on the junction of two slopes

Batten: Wooden plank on which roof covering is fixed

Cleat: Small wooden blocks fixed on principal rafter to

prevent purlin from sliding.

Pitch: The inclination of roof

Purlin: The member fixed on principal rafter along the

length of roof to carry common rafter or roof covering

Eave Board: Projection of roof beyond the surface of

wall is eave and the wooden board which covers the ends
of common rafters.

Valley: When two slopes meet together makes an inter-

nal angle

Wall plate: A long wooden member embedded on top of

wall to receive common rafter

Barge board: The wooden planks or boards which are

on the gable end of a roof

Verge: The edge of a roof running between the eaves

and ridge

Gable: The triangular upper part of a wall formed at the

end of a pitched roof.

245
Template : This is a square or rectangular block of stone
or concrete placed under beam or truss, to spread the
load over a large area of the wall.

Cleat : These are shorter section of wood or steel (angle

Iron) which are fixed on the principal rafters of trusses to
support the purlin.

Classification of Roofs

The roofs are classified into the following three catego-

ries.

i Pitched roof
4 Gambrel roof : This roof is like a gable roof, slopes in
ii Flat roof or terraced roof two directions. But there is a break in each slope shown
iii Curved roof in figure. (Fig 6)

i Pitched roof

A sloping roof is known as pitched roof.

Pitched roofs are basically of following forms:-

1 Lean to roof : This is the simplest type of steps roof

provided either for a room of small span or for verandah.
It has slope only one side a shown in figure. (Fig 3)

5 Mansard roof or curved roof : Mansard roof like a

hip roof slopes in four directions but each slopes have a
break thus sloping are formed. (Fig 7)

2 Gable roof : This is the common type of sloping roof

which slope in two directions. The two slopes meet at
the ridge. At the end face a vertical triangle is formed.
(Fig 4)

6 Deck roof : A deck roof has slope in all four directions

like a hip roof. But deck or plane surface is formed at the
top. (Fig 8)

3 Hip roof : This roof is formed by four sloping surface

is four directions. At the end faces sloping triangle are
formed. (Fig 5)

246 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.10.88
 Roofs

Pitched roof sloping roof Flat roof / Terraced roof Curved roof

Shell roof Domes

Madras terraced Bengal teraced
Basis forms

North light Berral vaud

shell roof shell roof

Lean to roof Gable roof Hip roof Gaimbel roof Mansard roof Deck roof

Classification

Single roof Double or purlin roof Trussed roof

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.10.88
King post Queen post Combination of king and queen Mansard truss Truncated truss Bell fast truss Steel truss Composite truss

247
Construction Related Theory for Exercise 2.10.90
Draughtsman Civil - Roof & roof covering

Roof covering for pitched roofs

Objective : At the end of this lesson, you shall be able to
• state the types of pitched roof covering materials.

Roof covering for pitched roofs 3 Initial cost and maintenance cost
4 Durability
Roof covering is an essential component of pitched roof
to be placed over the roof framework to protect it from 5 Availability of the material
main rain, snow, sun, wind and atmospheric agencies.
6 Fabrication facilities
Following points should be considered before selecting 7 Type of roof framework
the type of roof covering for a pitched roof.
8 Resistance to fire and heat
1 Climate of the locality 9 Special feature of the locality.
2 Nature of the building
Roof covering materials

Name Description
Fig 11
Thatch: Extensively used in sheds & villages
Cheapest & lightest material Unstable
against wind. Laid on battens.

Tiles: These are largely used various kinds of Fig 12

tiles are used. Commonly used for
covering sloped roof.

258
Poly New type material with high strength, Fig 13
carbonate heat insulation and good light trans
sheets mission. Good weather resistance and
UV protection.

Fig 14

Glass Structural glass slabs are available at in

different gauges. Fibre glass is both
strong and Height weight. Provide good
light transmission,good appearance,
etc.

Fig 15

Slates It is stratified rocks. Produced in large

number of sizes. Obtained from either
quarries or from mines.

Asbestos For AC sheets the cement is mixed with Fig 16

cement about 15% of asbestos fibres and the
sheets paste so formed are pressed under roll
(AC sheets) ers with grooves or teeth with series of
corrugations. They are used for facto
ries, workshops, garages, big halls etc.
Available in different trade such as big
six sheet, standard sheet, Trafford sheet
etc.

Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.9.90 259
 Fig 17

Shingles: Wood shingles are the sawn or split thin

pieces of wood obtained from well sea
soned timber resembling slates or tiles.
Generally restricted in hilly areas. Laid
in a manner as slates or tiles.

Corrugated Prepared by pressing flat wrought iron

Fig 18
galvanized plates between rollers with grooves or
iron sheet: teeth and then galvanized with coat of
zinc. Corrugations are present to in
crease strength and rigidity.

Fig 19

Ruberoid Light, flexible & waterproof, Not affected

by heat or cold & not attacked by fire.
Available in rolls.

260 Construction: Draughtsman Civil - (NSQF Level - 5): Related Theory for Exercise 2.10.90