ppt

1. TIMBER
SUBMITTED BY:-
HARPREET SINGH
ACADEMY OF APPLIED
ARTS

2. TIMBER:-
• Timber is a material which can be used for building
or carpentry and is derived from trees.It is organic
and renewable and can be used in a wide range of
applications.
• In order to make best use of timber in
environmental buildings we must understand how
timber is produced and how its natural properties
effect it as a building material.

4. CHARACTERISTICS OF GOOD TIMBER:-
• 1.HARDNESS:- A good quality timber should be hard
enough to resist deterioration.
• 2.STRENGTH:- It should have sufficient strength to
resist heavy structural loads.
• 3.TOUGHNESS:- It should have enough toughness to
resist shocks due to vibrations.It should not break in
bending and should resist splitting.Timbers having
narrow annual rings,are generally the strongest.
• 4.ELASTICITY:- It should have the property of elasticity
so as to regain its original shape after removal of
loads.This is a very important property to be considered
if the timber is used in making sport goods.

5. 5.DURABILITY:-
• It should be able to resist attacks of fungi and
worms and also atmospheric effects for a longer
period of time.
• 6.DEFECTS:- Timber should be prepared from the
heart of the sound tree and be free from sap,dead
knots,shakes and other similar defects.
• 7.FIBERS AND STRUCTURE:-It should have straight
and closed fibers and compact medullary rays.It
should give a clear ringing sound when struck.Dull
heavy sound is an indication of internal decay.Its
annual rings should be uniform in shape and colour.

6. STRUCTURE OF TIMBER:-

7. CLASSIFICATION OF TIMBER:-
• Various bases are considered for the classification
of timbers.The following are the important basis:-
• 1.Mode of growth.
• 2.Modulus of elasticity.
• 3.Durability.
• 4.Grading.
• 5.Availability.
• Classification based on mode of growth:-On the
basis of mode of growth trees are classified as
• 1.EXOGENEOUS
• 2.ENDOGENEOUS.

8. EXOGENEOUS TREES:-
• These trees grow outward by adding distinct
consecutive ring every year.These rings are known
as annual rings.Hence it is possible to find the age
of timber by counting these annual rings.
• These trees may be further divided into two parts:-
• 1.Coniferrous trees
• 2.Deciduous trees.

9. CONIFERROUS TREES:-
• Coniferrous trees are having cone shaped leaves
and fruits.The leaves do not fall until new ones are
grown.They yield soft wood.
• DECIDUOUS TREES:-Deciduous trees are having
broad leaves.These leaves fall in autumn and new
ones appears in spring.They yield strong wood and
hence they are commonly used in building
construction.

12. Endogeneous Trees:-
• These trees grow inwards. Fresh fibrous mass is in
the inner most portion. Examples of endogenous
trees are bamboo and cane. They are not useful for
structural works.
• Classification Based on Modulus of Elasticity:-
Young’s modulus is determined by conducting
bending test. On this basis timber is classified as:
Group A: E = 12.5 kN/mm2
Group B: E = 9.8 kN/mm2 to 12.5 kN/mm2
Group C: E = 5.6 kN/mm2 to 9.8 kN/mm2.

13. Classification Based on Durability:
• Durability tests are conducted by the forest
research establishment. They bury test specimen of
size 600 × 50 × 50 mm in the ground to half their
length and observe their conditions regularly over
several years. Then timbers are classified as:
High durability:- If average life is more than 10
years.
Moderate durability:- Average life between 5 to 10
years.
Low durability:- Average life less than 5 years.

14. Classification Based on Grading:
• IS 883-1970 classifies the structural timber into
three grades-select grade, grade I and grade II. The
classification is based on permissible stresses,
defects etc.
Classification Based on Availability:- Forest
departments classify timbers based on the
availability as
X—Most common. 1415 m3 or more per year
Y—Common. 355 m3 to 1415 m3 per year
Z—Less common. Less than 355 m3 per year.

16. DEFECTS IN TIMBER:-
• Various defects which are likely to occur in timber may
be grouped into the following three:-
(i) Due to natural forces
(ii) Due to defective seasoning and conversions.
(iii) Due to attack by fungi and insects.
(i) Defects due to Natural Forces: -The following
defects are caused by natural forces:
(a) Knots (b) Shakes
(c) Wind cracks (d) Upsets
(a) Knots:- When a tree grows, many of its branches fall
and the stump of these branches in the trunk is
covered. In the sawn pieces of timber the stump of
fallen branches appear as knots. Knots are dark and
hard pieces. Grains are distorted in this portion. If the
knot is intact with surrounding wood, it is called live
knot. If it is not held firmly it is dead knot.

17. (B) SHAKES:-
These are longitudinal separations in wood between
the annual rings.These are cracks which are partly
or completely separate fibres of wood.The
separations make the wood undesirable when
appearance is importent. The shakes are cracks in
the timber which appear due to excessive heat,
frost or twisting due to wind during the growth of
a tree.

20. STAR SHAKES:-
• These are cracks which extend from bark towards
the sap wood.These are usually confined upto the
plane of sap wood.These are wider on outside ends
and narrower on inside ends.They are usually
formed due to extreme heat or severe frost during
the growth of tree.

21. CUP SHAKES:-
• It appears as curved split which partly or wholly
separates annual rings from one another.It is caused
due to excessive frost action on sap present in the
tree especially when the tree is young.

23. HEART SHAKES:-
• These cracks occur in centre of cross-section of tree
and they extend from PITH to sap wood in direction
of medullary rays.These cracks occur due to
shrinkage of interior part of tree which is
approaching Maturity.The heart shake divide the
tree cross-section into two or four parts.

25. RING SHAKES:-
• When cup shakes cover the entire,they are known
as ring shakes.

26. RADIAL SHAKES:-
• These are similar to the star shakes and occur in
felled timber when exposed to the sun during
seasoning.
• Radial shakes are generally irregular,fine and
numerous.In this many splits are appeared.

27. RIND GALLS:-
• The rind means bark and gall indicates abnormal
growth.Hence peculiar curved swelling found on
the body of tree are known as rind gall.They
develop at points from where branches are
improperly cut off or removed.They are rarely found
in a tree and the timber in this part is very weak
and not durable.

29. VARIOUS TYPES OF TIMBER TREES ARE AS
FOLLOWS:-
• 1.DEODAR TREE
• 2.TALI TREE
• 3.TEAK TREE
• 4.MAHOGANY TREE
• 5.SHEESHAM TREE
• 6.BAMBOO TREE
• 7.KAIL TREE
• 8.CHIR TREE
• 9.MULBERRY TREE etc.
• Among these the most expensive wood is of TEAK
tree..which basic cost starts from rs 4500 and above.

30. SEASONING OF TIMBER:-
• The process of drying timber or removing moisture or
sap,present in a freshly felled timber,under more or
less controlled conditions is called seasoning of timber.
• Seasoning of wood is the first step in efficient utilization
of timber.
• Freshly felled timber contains a large quantity of
moisture roughly from 100 % to 200 %, based on dry
weight of wood.
• A well seasoned piece of wood contains 10‐12 %
moisture and will be in equilibrium with the
atmospheric humidity.
• The degree of moisture content is necessary for proper
retention of shape and size of component parts.

31. OBJECTIVES OF SEASONING OF TIMBER:-
• To minimize the tendency to shrink,warp and spilt.
• To reduce the weight for transport
purposes,handling,and thereby reduction in cost.
• To increase strength durability and electrical
resisting power.
• To improve wood working qualities in timber
including gluing,painting and polishing.
• To make it capable to a certain degree for
protection from attacks by insects and fungus.
• To make it fit for effective
preservation,treatment,otherwise the protective
coat will close the outside pores and induce decay.

32. METHODS OF SEASONING:-
• Air or Natural seasoning:-Also known as Air
Seasoning.
• Planks of green timber are laid down on battens
and have a gap between them to allow air to
circulate. Stickers or skids are the small pieces of
wood that allow the air travel between the planks.

33. Natural Seasoning:-
• The stack should be:
-Covered to prevent rain
damage while the planks dry
out.
-On a clean dry site
-All planks of the same species
and similar sizes should be kept
in the one stack
-The ends of the boards should
be protected from the sun to
prevent excessive drying-out.

34. Natural Seasoning:-
• Advantages of Natural
Seasoning:-
- No expensive equipment required
-Small labour cost once the stack is
-made
-Not wasteful of energy
• Disadvantages of Natural
Seasoning:-
-Slow drying rate
-Large area of space required
-Dependant on the weather
-Rate of seasoning cannot be
carefully controlled
-Only seasons to a MC of 18% - 22%

36. Kiln Seasoning(ARTIFICIAL SEASONING):-
• The lumber is placed in large kilns (ovens) where
temperatures, humidity and drying rates are
controlled.
• There are 2 types of kiln:-
-Compartment Kiln & Progressive Kiln

37. Compartment Kiln:-
• Timber is stacked similar to that in natural
seasoning only it is on a trolley which runs on rails.
1. The kiln is closed before steam jets in the walls,
ceiling and floor release heated steam.
2. The timber is allowed to heat up but not dry out.

38. Compartment Kiln:-
3. The relative humidity of the kiln is reduced
(controlled)while the heat is maintained.
(This allows moisture in the wood to
evaporate gradually).
4. Fans circulate the air around the kiln.
5. Air vents allow moist wet air out and fresh
air in.

39. Progressive Kiln:-
• The progressive kiln is a continuous kiln. The timber
goes through the various stages of drying as it
moves through the kiln on a trolley. The drying
process is the same as that for the Compartment
Kiln.

40. Kiln Seasoning:-
• Advantages of Kiln Seasoning:-
-Quicker due to higher temperatures, ventilation and
air circulation
-Achieves a lower moisture content
-Provides greater degree of control during the drying
process
-Allows more precise rates of drying
-Allows uniform circulation through the stack
-Control over moisture content and rate of drying can
be achieved
-Artificial defects can be controlled.
• Disadvantages of Kiln Seasoning:-
-It is expensive
-Requires supervision by a skilled operator
-Is dependant on energy.

42. VENEER:-
• Veneer is very thin timber that is cut 3 millimetres or less and used to cover
either particle board or MDF to give the surface a wood grain appearance.
• Strips of this wood are also used to make plywood as it is glued in layers to make
it light weight and strong.
This product is widely used in woodwork because it is a useful product that is
used to make cheaper furniture like particle board look more like high quality
furniture.
• More expensive timbers are usually used when making it to increase the quality
look and feel of the product it is being applied too. MDF and particle board can
also be covered with a plastic laminate but it does not give a quality feel like
strips of wood do.
It is fairly easy to bond to manufactured fibreboards, panels and flooring as long
as the surface is relatively flat and a good adhesive is used such as PVA glue.
• You can also buy this product raw so that a finish of some sort can be applied to
increase the strength, durability and appearance of the wood.
• If you are attempting to Glue your own veneer to a manufactured board you must
be very careful and delicate because it does not take much to damage the sheets.
• Also try not to leave any unwanted marks or dirt on the sheets because it may be
difficult to remove as you generally can’t sand it because of how thin the sheets
are

44. PLYWOOD:-
• Plywood is another manufactured board that it is made from layers of solid timber veneer
that are usually about 3 millimetres thick. Because it is made in layers it is incredibly strong
but also light in weight.
• The interior layers of these boards are usually made from an inexpensive wood while the
outer veneer layers are made from more expensive timber to give the board a nice wood
grain appearance.
This type of board is manufactured from layers of veneer that are glued together and
compressed under heat, they are then cut into appropriate sizes. With each new layer of
veneer added the grain is rotated at 90 degrees each time, this is done to maximise the
boards strength and to prevent warping and twisting.
This manufactured board is used as a more affordably option to solid timber or as an
alternate to other manufactured boards. You are most likely to see this wood used in
places such as school desks, furniture, wood panelling and some flooring although usually
only the faces are shown due to the unattractive look of the edges.
Advantages:
• Very strong
• Light
• Resists cracking, bending, warping, and shrinkage
• Can be made from most timbers to increase aesthetics
• Good for wood panelling

47. VARIOUS TYPES OF
PLYWOOD:-

48. LAMINATE PARTICLE BOARDS:-
• On the normal particle/fibre board, when the laminate-design-paper is pasted then it is
called ‘Laminated Particle/fibre Board’. This design paper is pasted on the hot-press and is
on both sides of the board. The resin used for pasting is Phenol Formaldehyde or of similar
grade. The design paper is pasted on both sides in order to prevent the warpage.
Thicknesses of these sheets available are 6mm, 8mm, 10mm, 12mm, 15mm, 18mm and
25mm. The overall sizes available are 1.22 m x 2.44 m, 1.84m x 2.74 m and 1.84 m x 3.66 m.
• The desired design paper may be on one side or both sides. When it is on one side it
is called ‘One side laminated board’. Even though it is called one side laminated board, on
the other side some neutral coloured sheet like off-white or white is pasted in order to
prevent warpage. When the desired design sheet is on both sides, it is called ‘Both side
laminated particle board’.
• Like plywood and fibre/particle board, we get both kinds of Laminated Particle boards
in view of water resistance. That is we get Marine or waterproof laminated boards and
ordinary or commercial grade. Normally these are called ‘Exterior grade’ and ‘Interior grade’
respectively.
• Furniture made with laminated particle board has following advantages.
• i] It works out cheaper by 15% than the one made with plywood and laminate.
• ii] The process time to erect is shorter with laminated particle board.
• iii] The laminated particle board furniture looks much neater and cleaner than the plywood
and laminate type.
• iv] The particle boards are never attacked by termites whereas; this is not the case with
plywood.
• v] The particle boards are ecofriendly since they save the trees whereas, plywood warrant
tree cutting for manufacture.

50. FIBRE BOARD:-
• Medium Density Fibreboard (MDF) is a reconstituted wood panel product. It
is a dry-processed fibreboard manufactured from wood fibres, as opposed
to veneers or particles, and is denser than plywood and particleboard. MDF
has an even density throughout and is smooth on both sides.
• MDF is reconstituted into wood sheets in a variety of widths and lengths.
Bonding is achieved by the addition of synthetic resin adhesives, which are
cured under heat and pressure. Paraffin wax is added to assist with water
repellency, while other chemicals can be added during manufacturing for
more specific protection.
• MDF is primarily used for internal use applications,interior
finish,panelling,suspended ceilings partitions,flush doors,table tops etc. It is
available in raw form with a fine sanded surface or with decorative overlay
such as wood veneer, melamine paper or vinyl.
• Note: Other general purpose dry-processed fibreboards are available, being
Ultra Low Density, Low Density, High Density (HDF) and High Performance
(MR only). These tend to be specialty products, so further information
about their usage should be confirmed directly with the manufacturer.

52. BATTEN BOARDS:-
• The boards having core slab consisting of strips
which are glued together between two veneers,one
on either side are known as batten boards or black
boards.
• USES:-These are used for making
partitions,floors,panelling,table tops etc.