BUILDING MATERIALS AND CONSTRUCTION II

TIMBER
 TIMBER
• The wood which is suitable or fit for
construction or engineering purposes is
called timber
• It is a sustainable, affordable and
versatile construction material which
has been used for construction
purposes for centuries.
Name origin

Timbrian
Timber (An old To
English word) build
 USES OF TIMBER
• BUILDING CONSTRUCTION
• HOUSE POST CONSTRUCTION
• BEAMS AND RAFTERS
• CONSTRUCTION OF BRIDGES AND BOATS
• FURNITURE AND INSTRUMENTS
• RAILWAY SLEEPERS AND PACKING CASES
• TOYS AND ENGRAVING WORK
• FORMWORK OF CEMENT CONCRETE
General Properties
❖ Color – a darker color in wood indicates greater durability.
❖ Odor – it is present only on freshly cut trees.
❖ Hardness – is the ability of wood to withstand indentations caused by harder
bodies.
❖ Density – densest woods are generally the strongest.
❖ Grain - Depending on the actual alignment, the grain may be straight, spiral,
interlocked, wavy or irregular.
a) Spiral Grain
b) Interlocked Grain
c) Wavy Grain
❖ Texture - In hardwoods, the texture depends upon the size and distribution
vessels and rays. In softwoods, it is determined by the size and distribution of
tracheid.
Moisture of Timber

• Moisture Content - It is one of the most important

characteristics of timber that affects its use on the
site performance.
• Equilibrium Moisture Content (EMC) - moisture content of
wood changes in response to the temperature and
humidity of its surroundings.
• Fibre Saturation Point (FSP) – when the cell cavities
are empty but the cell walls still retain their bound
water.
SEASONING

• Fresh timber which is obtained from trees have about 30 to 40

percent sap or moisture. This sap is very harmful for the life of
the timber.
• Therefore it is essential to remove the sap by applying certain
special methods.
• All such methods are collectively termed as seasoning of timber.
TYPES OF TIMBER SEASONING

Timber seasoning

Natural seasoning

Artificial Water
seasoning seasoning
NATURAL
SEASONING
Artificial
seasoning Kiln seasoning
Chemical
seasoning Electric
seasoning
Advantages of seasoned timber

• It has reduced weight

• Strong and durable
• Resistance to decay and rot
• Takes high polish
• Easier to work with
• Lasts longer
Defects in timber

Defects caused in timber may be basically classified into

two categories:
❖Internal Defects – due to factors affecting the growing tissue.
❖External Defects – due to external agents or subsequent treatment
of timber.
Defects in Timber

• The defects occurring in the

timber are grouped as follows :-
1. Defects due to conversion
2. Defects due to fungi
3. Defects due to insects
4. Defects due to natural forces
5. Defects due to seasoning
Defects due to conversion
• During the process of converting timber to the
commercial form, the following defects occur:-
a) Chip mark- marks or signs placed by chips on
the finished surface of timber.
b) Diagonal grain- Due to improper sawing
of timber.
c) Torn grain- Caused when a small depression is
formed by falling of a tool or so.
d) Wane- Denoted by the presence of original
rounded surface on the manufactured piece
of timber.
Defects due to
fungi
Fungi attack timber only when the following two conditions
are satisfied simultaneously:
i. The moisture content of timber is above 20%.
ii. There is presence of air and warmth for the growth of fungi.

Following defects are caused in the timber by the fungi:

• Blue stain- sap of wood is stained to bluish color.
• Brown rot-decay or disease of timber.
• Dry rot- converting of timber into dry powder form.
• Heart rot- indicated by the hollow sound given out when
struck
with a hammer.
• Sap strain-loses the color of sap.
• Wet rot- causes chemical decomposition of wood of timber.
• White rot- opposite of brown rot.
Defects due to insects
and natural forces
Insects which are usually
responsible for the decay
of timber:-
• Beetles
• Marine borers
• Termites
Natural forces causes:
• Abnormal growth
• Rupture of tissues
Defects due to natural
forces
• Burls- growth of the tree is upset and irregular projections appear.
• Callus- soft skin which covers the wound (Bark) of the tree.
• Chemical stain- discoloration of wood.
• Coarse stain- annual rings get widened.
• Dead wood- timber obtained from dead trees.
• Druxiness- white decayed spots which are concealed by healthy wood.
• Foxiness- indicated by red or yellow tinge in wood.
• Rind galls- these are typical curved swelling formed upon the trunk of the
tree by successive layer of the sapwood.
• Twisted fibers- fibers or wandering hearts are caused by the
prevalent wind turning or twisting the tree at its young age
constantly in one direction.
• Upsets- are clipping or buckling of fibers caused by crushing of fibers
when the trunk is felled violently over a rocky surface.
• Water stain- discoloration due to water exposure.
• Wind cracks- are shakes on the outside of a log due to the shrinkage of
the exterior surface caused by the atmospheric influences.
Defects due to
seasoning
Following defects occur in the seasoning process of wood:
• Bow- a curvature of the timber in the direction of its length.
• Case-hardening- it is due to the unequal drying of the
exterior surfaces under compression and the interior
surfaces under tension due to rapid drying.
• Check - these reduce the shearing resistance of the wood.
• Collapse - the cells of timber are flattened due to excessive
shrinkage.
• Cup- a curvature in the transverse direction of the timber.
• Honeycombing- separation of the fibers in the interior due to
drying stresses.
• Radial shakes- cracks in radial direction (from centre of the tree to
outward)
• Split- separation of the fibers along the grain and extends from
one
end of the plank to the other.
• Twist- a spiral distortion along the length of the timber.
Knots
• Knots - are dark, hard pieces occurring as signs of branches broken or cut off.
❖ According to size (diameter)
▪ Pin Knot – not more than 6.5mm
▪ Small Knot - more than 6.5mm but not more than 20mm
▪ Medium Knot- more than 20mm but not more than 40mm
▪ Large Knot- more than 40mm
❖ According to form
▪ Round or Oval Knot- a knot cut more or less at right angles to its long axis so that the exposed is round or
oval.
▪ Splay or Spike Knot- a knot cut approximately parallel to its long axis so that the exposed section has
an elongated shaped.

❖ According to quality
▪ Live Knot- a knot whose fibers are completely intergrown with those of the surrounding wood.
▪ Sound Knot- a live knot free from decay.
▪ Tight Knot- a live or dead knot held firmly in place
▪ Dead Knot- a knot whose fibers are not intergrown with those of the surrounding wood. According to quality
▪ Loose Knot- a dead knot which is not held firmly in place.
▪ Knot Hole- a hole left as results of the removal of a knot.
▪ Decayed Knot- a knot softer than the surrounding wood, and containing decay.
Shake
s
• Shakes- or cracks are caused by the rupture
(tearing or breaking ) of tissues resulting in
partial or complete separation of the fibers
along the grain.
❖ Star Shakes: cracks that occur from the
pith.
❖ Heart Shakes: cracks in central part
❖ Cups Shakes: cracks along growth of rings
but in cup or concave shape.
❖ Ring Shakes: cracks along the growth of
the ring of the trees.
❖ Radial Shakes: Cracks in radial direction
(from centre of the tree to outward
(bark))
Objects of preservation of timber

• The preservation of timber is carried out to achieve

the following three objects:-
• To increase the life of timber structures.
• To make the timber structures durable.
• To protect the timber structures from the attack
of destroying agencies such as fungi, insects, etc.
TIMBER
PRESERVATIVES
The main classes of timber preservatives are :
• ACSU(Ammoniacal quaternary solution) treatment
• Chemical salts
• Coal tar is highly effective against fungi.
• Creosote oil
• Oily substances insoluble in water
• Water soluble salts
Zinc chloride is the most extensively used of this type. It is
clean and odourless.
Availability and uses of timber
• Common Timber
❖ Teak - The sapwood is pale yellowish or greyish-white in color and is distinguished from
heartwood. The heartwood is golden brown and turns a dull deeper brown on exposure.
❖ Deodar - The sapwood is white to creamy white and is distinct from the heartwood
which is light yellowish brown turning to pinkish brown on exposure.
❖ Chir - The sapwood is white to creamy white and is distinct from the heartwood which is
light yellowish brown turning to pinkish brown on exposure.
❖ Kail - The yellowish in white to greyish sapwood is white to pale-yellowish white in color and
is distinct from the heartwood which is light pinkish-red to light red.
❖ Sisso - Sapwood of sisso is pale yellowish or greyish white and is distinct from the
heartwood which is golden brown or dark brown in color.
❖ Sal - The sapwood is pale-yellowish or brownish white and is distinct from the
heartwood which is brown or reddish brown.
❖ Mango - This is brown in color.
TIMBER PRODUCED IN INDIA

• There are over 150 species of timber which are produced in

India. Following are the chief varieties of timber trees
which are used for engineering purposes in India:
 Veneer
Industrial s
Plywoods
timber
Fibre boards Impreg
timbers Compreg
timbers
Block board and laminboard
Glulam (Glued Laminated timber)
• Scientifically prepared
Flushdoor
timber in a factory.
shutters
• They possesses Particle board or clip
desired shape, board
Hardboard
appearance,
strength, etc.
Veneers (IS:303-
1989)
• These are thin sheets or slices of wood if superior quality whose thickness varies from
0.40 mm to 6 mm or more.
• They are obtained by rotating a log of wood against a sharp knife of rotary cutter or
saw.
• The veneers after being removed are dried in kilns to remove moisture.
• Veneers may be glued with suitable adhesives on the surface of inferior wood.
• Used to produce plywood, batten boards and lamina boards.
• May be fixed on corners or bent portions.
• Indian timbers suitable are mahogany, oak, rosewood, sissoo, teak, etc.
Plywood
• Plywood is a panel formed of three or more layers of veneer glued together, usually
with the grain of adjacent veneers running at right angles to each other, held in
position by the application of suitable adhesives.
• The perpendicular placing increases longitudinal and transverse strengths of plywood.
• The plywood are available in different commercial forms such as batten board,
lamina board, metal faced plywood, multiply, three-ply, veneered plywood, etc.
• According to CPWD specifications, plywood for general purposes are of following three
grades:
i. Boiling Water resistant
ii. Warm water resistant
iii. Cold water resistant
Thickness
Dimensions (sizes of plywood)
Tolerance of
plywood
Advantages of
plywood
❖It has a good strength both across as well as along the grain.
❖Plywood has better splitting resistance due to grains in adjacent layers
running at the right angle and nailing and screwing even closed to the edges
in safe.
❖Can easily be bending to a curvature limited by the tensile and the
compressive
strength of the other plies.
❖The face piles made at different heartwoods show great aesthetic variety
in grain pattern and color.
Hardwood
• Hardboard - manufactured from raw materials like
wood waste, veneer manufacturing, furniture
making.
❖ Sizes of hardboards
▪ Medium hardboard
▪ Normal hardboard
▪ Tempered hardboard
Thickness of Hardboards
Width and Length of Hardboards
• Fibre Board: Rigid boards and they are known as the pressed wood or
reconstructed wood. The fibre boards form an ideal base for all types
of decorative finishes like distemper, oil paint, etc.
• Impreg timbers: Timber which is fully or partly covered with
resin and used for moulds, furniture, decorative articles, etc.
• Compreg timbers: Almost with same properties as of above, it is
treated under high pressure. The strength and durability is
more.
• Block boards or lamin boards: it is a board having core strips,
each not exceeding 7 mm in thickness
• Glulam: Glued and laminated wood made of solid wood.
• Flush door shutters: More popular for interior works.
• Particle boards: is a board manufactured from particles of wood
 Marke
forms
t Batte
n

oftimber
Baulk
Board
Deal
End
Log
Plank
Pole
Quartering
Scantling
 Batten has Baulk is a Board is a Deal is a piece End is a short
breadth and roughly plank whose of soft wood piece of
thickness Squared timber thickness is less with parallel batten, deal,
which does not piece and it is than 50 mm sides which has scantling.
exceed 50 mm. obtained by and width a width limited
removing bark exceeds 150 upto 230 mm.
and sap wood. mm.
 Scantling are the
Log is a trunk of Pole is a sound
Plank is a timber Quartering is a pieces if
tree obtained long log of wood.
piece with square piece of miscellaneous
after removal Also called as a
parallel sides. timber. sizes of timber
of branches. spar.
sawn out of a log.
ADVANTAGES OF
TIMBER
❖ Can be easily handled and joined.
❖ Timber can be used for both load bearing structures and non-load bearing
instruments.
❖ It can be easily converted to any shape and size.
❖ With the advent of superior adhesives and other forms of timber connectors.
❖ The wastage in timber construction is less because all wastes can be put one use or
the other.
❖ It has high resale and salvage value.
❖ Timber has better insulating properties than any other materials.
❖ Durability of timber can be very high, if properly seasoned and preserved.
❖ Timber constructions are light in weight and strong and can be made economical.
❖ For aesthetic and decorative appearance.
❖ Easily available.
Joineries
• Joinery is a part of woodworking that involves joining together pieces
of timber or lumber, to produce more complex items. Some wood joints
employ fasteners, bindings, or adhesives, while others use only wood
elements. The characteristics of wooden joints - strength, flexibility,
toughness, appearance, etc. - derive from the properties of the materials
involved and the purpose of the joint. Therefore, different joinery techniques
are used to meet differing requirements. For example, the joinery used to
construct a house can be different from that used to make puzzle toys,
although some concepts overlap.
 CARPENTARY JOINTS

Carpentry joint are joints between two

wooden pieces .
Some wood joints employ fasteners, bindings,
or adhesives, while others use only wood
elements.
Characteristics of wooden joints - strength,
flexibility, toughness , appearance, etc. -
derive from the properties of the joining
materials and from how they are used in
the joints.
 JOINING COMPONENTS

Fasteners

Carpentry Glue /Adhesive

JOINING COMPONENTS
 TYPES OF JOINTS

• Lengthening Joint
• Widening Joint
• Bearing Joint
• Framing Joint
• Angle or Corner Joint
• Oblique Shoulder Joint
 LENGTHENING JOINT
LAP JOINT
• Used extensively in construction and cabinetry for framing.
• Quick and easy to make and provide reasonable strength through good
gluing surface.
• They may be reinforced with dowels or mechanical fasteners to resist
twisting.

Dowels
A joint made by halving the thickness of each member at the joint
and fitting them together.
T-HALF LAP JOINT
(All dimensions are in mm)
HALF LAP CROSS JOINT
(All dimensions are in mm)
 WIDENING JOINTS
BUTT JOINT
End are butted together. Usually glued or nailed together.
It’s weakest joint.
 WIDENING JOINTS
TONGUE AND GROOVE JOINT
•A method of fitting similar objects together, edge to edge.
•Used mainly with wood: flooring, paneling, doors and similar
constructions.
•Tongue and groove joints allow two flat pieces to be joined strongly
together to make a single flat surface.
 BEARING JOINTS
DOVE TAIL JOINT
Its a form of box joint where the fingers are locked together by
diagonal cuts.
The sides of each half of the joint are cut at an angle of about 30
degrees so that when the joint is assembled , the separate pieces
are locked together.
Stronger than lap or butt joint .
 BEARING JOINT
BOX JOINT
• The strength of a finger joint comes from the long-grain to long-grain contact
between the fingers, which provides a solid gluing surface.
• Number of contact points also allows for more gluing surface as opposed to a butt
joint.
• The joint is made by cutting a set of complementary rectangular cuts in two
pieces of wood, which are then glued.
• To visualize a box joint simply interlock the fingers of your hands at a ninety
degree angle.
 BEARING JOINT
MORTISE AND TENON JOINT
• The mortise(hole) and tenon(peg) joint is simple and strong.
• The tenon is formed to the end of a member generally referred to
as a rail and is inserted into a square or rectangular hole cut into the
corresponding member. The tenon is cut to fit the mortise hole
exactly and usually has shoulders that seat when the joint fully
enters the mortise hole.
• The joint may be glued, pinned, or wedged to lock it in place.
MORTISE & TENON JOINT
MORTISE & TENON JOINT
(All dimensions are in mm)
 OBLIQUE JOINT
BRIDLE JOINT

The distinguishing feature is that the tenon and the mortise are cut to the full
width of the tenon member.
 ANGLE/CORNER JOINT
Used to Join corners of frame.
MITER JOINT
A miter joint is a joint made by beveling each of two parts to be joined, usually
at a 45° angle, to form a corner, usually a 90° angle. For woodworking, a
disadvantage of a miter joint is its weakness, but it can be strengthened with a
spline.
CARPENTRY TOOLS
THANKS…ANY DOUBTS?