ROOF COVERINGS

Roof covering is a
material covering
provided over the
form-work of roof
structure to act as a
barrier for the rain
,sun ,wind or other
such elements
Types of roof coverings

SHINGLES
TILES
ASBESTOS-CEMENT SHEETS
CORRUGATED GALVANISED IRON SHEETS
SLATES
FIBRE GLASS SHEETS
ALLUMINIUM SHEETS
ASPHALT SHEETS
 Shingles

Roof shingles are a roof

covering consisting of
individual overlapping
elements. These elements are
typically flat rectangular
shapes laid in rows from the
bottom edge of the roof up.
Shingles have been made of
• Shingles are
various materials such
obtained in
as wood, slate, asbestos-
lengths varying
cement, bitumen-soaked
from 30cms. To
paper covered with aggregate
38cm. And
(asphalt shingle), composite
width 6cm to
or ceramic.
25cm
 HOW TO FIX SHINGLES ON THE ROOF

•First, locate the exact center of the roof and

mark it with a chalk line.
•Center your first shingle on the chalk line–
directly on top of the starter strip–and nail it
into position.
•Use four nails in each shingle, located in the
position. Always drive the nails straight in and
never at an angle, as they could cut the shingle
and cause leaks.
•Each succeeding shingle should bump up
against the center shingle. Continue applying
the shingles to the end of the roof in each
direction
 Tiles
Roof tiles are designed mainly to
keep out rain, and are traditionally
made from locally available
materials such as clay or slate.
Modern materials such
as concrete and plastic are also used
and some clay tiles have a
waterproof glaze.
The commonly used tiles are FLAT PAN
TILES; HALF ROUND COUNTRY TILES;
MANGLORE TILES
Roof tiles are 'hung' from the framework
of a roof by fixing them with nails. The
tiles are usually hung in parallel rows,
with each row overlapping the row below
it to exclude rainwater and to cover the
nails that hold the row below
 Asbestos Cement Sheets
Asbestos cement sheet is a product employed
broadly in the past as a building material. It
commonly has 10-15% asbestos fibres which are
bound in portland cement or ca silicate and the
uncoated sheets are light grey in colour .
 The sheets are light,cheap, impervious,durable

• Lightweight and easy to handle.

• Ideal for new, existing or temporary
roof coverings
• Chemical and corrosion resistant.
• Rust, rot, and frost resistant.
 How to fix asbestos sheet?

 The sheets should be laid with smooth side

upwards.
They are usually laid with end lap of 15cm.
The holes for fixing accessories must be
drilled and not punched.
The diameter of the hole should be 3mm.
Greater than the diameter of the screw or bolt
to be used.
A bitumen washer must be provided under
G.I flat washer with each bolt or screw.
‘J’ bolts should be used for angle purlin and
crank bolts should be used used for purlins.
The unsupported overhang of the sheets at
the eaves should not preferably be more than
30cm.
 Corrugated Galvanized Iron Sheets
•Corrugated galvanised iron (colloquially corrugated
iron commonly abbreviated (CGI) is a building
material composed of sheets of hot-dip galvanised mild
steel, cold-rolled to produce a linear corrugated pattern in
them.
•CGI is lightweight and easily transported . It is widely used
especially in rural and military buildings such as sheds and
water tanks.
MANUFACTURING
•Today the corrugation process is carried out using the process of
"Roll Forming".
• In the corrugation process sheet metal is pulled off huge rolls
and through rolling dies that form the corrugation.
• After the sheet metal passes through the rollers it is
automatically sheared off at a desired length.
•The most common materials are ferrous alloys but may also
span to stainless steels. Copper and aluminium are also used.
 Fixing of C.G.I. sheets
 G.I. sheets are usually 60 to 70cm
wide,150cm long and 1 to 2 mm thick these
sheets, like A.C sheets can be fixed to timber
purlins .
 Line up the first panel at the bottom corner
of the roof near the lip and hammer it in place
with 3-inch metal roofing nails.
 Line up the second sheet overlapping the
first by one ridge and install it in the same
manner. Set the third piece in place and
continue until all of the first row has been
installed.
 Insert the ridge cap along the bottom edge
of the panel.
 They are laid on the roof with an end lap not
less than 15cmover the sheet below it and the
side lap should extend from 1.5 to 2
corrugations .
Various types of C.G.I. sheets Galvanized Screw

Fixing Details
 Slates
• Slate is one of the most aesthetically pleasing
and durable of all roofing materials.
•Slate is a fine-grained, foliated,
homogeneous metamorphic rock derived from
an original shale-type sedimentary
rock composed of clay or volcanic ash through
low-grade regional metamorphism.
• Many slates will form smooth flat sheets of
stone which have long been used for roofing and
floor tiles and other purposes.
• It can be found in many shades of grey, from
pale to dark, and may also be purple, green
or cyan.
• Slate is particularly suitable as a roofing
material as it has an extremely low water
absorption index of less than 0.4%.
 • The common size of slates vary from
60cm*35cm to 25cm*12cm.
• The thickness of the regular size stone slate
varies from 1.6mm to 4.8mm.
• The slates may be fixed on the battens fixed on
the timber rafters, or they may be laid on
wooden boarding fixed on the roof framework.

• Slate roof tiles are usually fixed

using either nail fixing, or the hook
fixing method.

• Its low tendency to absorb water

also makes it very resistant to frost
damage and breakage due to freezing.
 FIBER GLASS ROOFING
•Fiberglass is a fiber reinforced polymer made of
a plastic matrix reinforced by fine fibers of glass.
•Fiberglass is a lightweight, extremely strong, and robust
material.
•The material is typically far less brittle, and the raw materials
are much less expensive.
•It is used as a reinforcing agent for many polymer products.
•Fiberglass roofing offers flexibility, malleability, and
versatility.
•Corrugated fiberglass roofing and panels are the ultimate
choice for roofing projects requiring high tensile strength. Properties

•Excellent waterproofing characteristics.

•Can be used in extreme climatic condition.
•High insulation and sound absorbency values.
•Resistant to corrosion-does not rust or rot.
•Available in a range of environmentally sensitive colours.
Requires minimum maintenance.
•Contains no hazardous chemicals.
 Installation

1. Provide a minimum of one corrugation overlap at sides.

2. Provide 8" end-lap for roof with pitch of less than 4" in 12"; 6" end-
laps for pitches or more than 4" in 12".
3. Fasten panels through crowns at every second corrugation. Fasteners
with washers are recommended. Space fasteners 6" to 8" on center at
panel ends: 12" to 16" on center for intermediate purlins and siding
applications.

SIZE AVAILABLE

Fibers available in widths of 2-4

feet and lengths of 6-16 feet.
 Costing

•Compared to traditional roofing materials like felt and bitumen fiber

glass is much more expensive but it is very long lasting hence the cost
gets balanced. In some cases it falls cheaper due to easy installation,
reduced need to strip out existing material.

Strength

It is strong enough to bear weather effects and even strong enough

to walk on. Can be used as roof gardens balconies and patio areas.
 Steel Trusses

•A truss is a structure comprising one or more triangular units constructed

with straight members whose ends are connected at joints referred to
as nodes.
•A trusses consist of an assembly of rigid but elastic member jointed in the
form of triangles to act as a beam.
•Out of various shape of steel section , angles are considered most suitable
for steel roof truss.
•This is on account of the fact the angles can resist both compressive and
tensile stresses effectively.
Section Of Steel Truss
Detail Of Joint In Truss
Types Of Trusses
 King Post Roof Truss

•It is a form of roof truss which is commonly used for

spans varying from 5-9mts. It consists of a frame work
,comprising of two principal rafters ,one tie beam, two
strut and a king post.
•The trusses are connected to each other through
purlins which are placed at right angles to sloped
rafters and are secured to them through cogged joints
and cleats.
•The purlins also support the common rafters upon
which roof coverings is laid.
 Queen Post Roof Truss

•For spans greater than 9-14mt. Queen post is

commonly used. It may be defined as frame work
consisting of two principal rafters, two queen post
one straining beam, two inclined struts and a
straining sill. It differs from king post in having two
vertical tension members called queen post.
•The heads of the queen post are strutted apart by a
horizontal member termed as straining beam
 MARKET SURVEY
 Two types are available—1/. Normal G.I. Sheets. 2/.Plastic Coated G.I. Sheets
 Thickness – 0.5 mm.(26 Gauge) 90% used in India. Available in market- 22, 24, 28, 30
Gauge.
 Width- 3.5 feet, which will cover 3.25 feet.
 Length – 8ft, 10ft, 12ft. By order- 40 ft. But usually not recommended more than 25
feet because fixing becomes difficult and difficult to handle.

 RATE -:
 Powder Coated G.I. Sheets- 68 Rs/Kg.(Including Fixing.)+ 4%tax.
 G.I. Sheets- 53 Rs/kg.(Including fixing) + 4% tax.
 Patterned G.I sheets –rs74/kg
 Manufacturers Of G.I. Sheets-:
 Jindal, Bhushan, SR PUNA , National. ( Sheets Are Further Profiled according to
design.)
 Note-: Now in fixing screws are more preffered than J-Bolt or U-Bolt. Main
manufacturer of screw is Corroshield Company.
..
 fibre glass sheet is available at the cost of Rs2000/ft.
 Ms plate is available at rs40/kg
 Angles are available at the cost of rs38/kg
 Main manufacturers are lyod ,asian, essar,bocaro.
 Main manufacturers of tiles are kataria tiles.
