UNDERSTANDING ABOUT TIMBER AND ITS USES AS BUILDING MATERIALS AND DEFECTS IN TIMER, SEASONING OF TIMBER http://www.youtube.com/c/beaCIVILEngineergovindsir_onlineclasses

1. TIMBER
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from desk of
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2. TIMBER
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Construction
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 TIMBER: The wood which is
suitable or fit for engineering
construction or engineering purpose
is called timber. It should have
structural as well as aesthetic merits.
 WOOD: The organic matter
obtained from trees is called wood.
 LUMBER: The sawed wood meant
for construction in the form of
boards is called lumber.

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• There is difference between terms timber and wood.
Wood includes all types of wood which may be
burning wood, structural wood, furniture wood etc.
• But wood suitable for use as a structural material is
called timber.
• So we can say: Wood is usually used to refer to the
material in its natural state...
• timber refers to it after it has been modified by man.
• So you go to the forest to collect wood for the fire,
and to the DIY store to get timber for doing up your
house
GENERAL

4. Timber is obtained from trees. Timber denotes structural
wood. A standing living tree is known as standing
timber.
Rough timber.
When tree has been cut and its stem and branches
are roughly converted into pieces of suitable lengths.
Converted timber
When roughly converted timber is further sawn
and converted into commercial size the planks, logs,
battens, posts, beams, etc
GENERAL
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5. TYPES OF TREES
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Trees are classified into two groups depending upon growth
pattern.
 Endogenous trees: The trees which grow inwards in
longitudinal fibrous mass are called endogenous trees.
 Exogenous tress : The trees which grow in out wards across
horizontal section of stem are called exogenous trees. These
trees are only fit for engineering construction. Exogenous
trees are again subdivided in to two types.
 Conifers or Evergreen: They give soft wood. They have
pointed leaves. Examples: Deodar Pine Chir Kail,etc.
 Deciduous: These have hard wood. These have broad
leaves. Examples: Teak Sal Shisham, etc.

6. GENERAL PROPERTIES
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 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.

7. IDENTIFICATIONS OF TIMBER
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 Luster- is the ability to reflect light beam pointedly.
 Workability- the relative case in which wood is shaped cut and
fastened together than the others. Warping- is the general term
used to describe any variation from a true surface.
 Moisture content- is a percentage of the mass of water over the
mass of wood fibre in a piece of timber.
 Specific Gravity- is the ratio found by dividing the weight of a
substance by the weight of an equal volume of pure water.

8. MOISTURE OF TIMBER
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 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.

9. SEASONING OF TIMBER
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 Fresh timber which is obtained from trees contains about 30
- 40% of moisture.
 This sap is very harmful for the life of a timber.
 Therefore, it is necessary to remove that sap by applying
some special methods.
 All those methods which are used for removing the sap from
timber are collectively termed as SEASONING OF
TIMBER.

10. ADVANTAGES OF SEASONED TIMBER:
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It reduces weight.
It makes strong and durable.
It increases the resistance to decay or rot.
Takes more polish.
It makes easier to work.
Its life is increased.

11. TYPES OF TIMBER SEASONING
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The main types of timber seasoning are as under.
(1)Natural Seasoning
(2)Artificial Seasoning
(a) Kiln Seasoning
(b) Chemical Seasoning
(c) Electric Seasoning
(3) Water Seasoning.

12. 1. Natural Seasoning:
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 In the air seasoning or natural seasoning or natural drying,
seasoning of timber, timber is dried by direct action of air, wind
and sun.
 In this method, the timber logs are arranged one over the other,
keeping some space or distance between them for air circulation
of fresh air.
 Generally this type of seasoning requires few months to over a
year, this is very slow process.

13. 2. Artificial Seasoning:
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a) Kiln Seasoning:
 In kiln seasoning timber is placed in a chamber with
some special heating arrangement.
 In this process one thing should be kept in mind that
heating system should be under control, other wise
timber will be crack or wrap.
 The time required for this seasoning is 3 to 12 days.
This is quick process.

14. 2. Artificial Seasoning:
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b) Chemical Seasoning:
 In chemical seasoning carbon dioxide, ammonium
carbonate or urea are used as agents for seasoning,
those are applied in dry state.
 The interior surface of timber dries first than outer side.
 This ensures uniform seasoning.
 The time required for this seasoning is 30 to 40 days.
c) Electric Seasoning:
 In this method electric current is passed through the
timber logs.
 The time required for this seasoning is 05 to 08 hours.

15. 3. Water Seasoning:
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 In water seasoning, timber logs are kept immersed whole in the
flowing water.
 The sap present in timber is washed away.
 After that logs are taken out from water and are kept in open
air, so water present in timber would be dried by air.
 The time required for this type of seasoning is 2 to 4 weeks.

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Following are the qualities of good timber.
 A good timber should be hard and durable.
 It should be capable of resisting the actions of fungi, chemicals
and physical agencies.
 The fibers of the timber should be straight and compact.
 The timber should be free from knots wists, upsets, burls
shakes, flaws
 Its color should be dark. It should be obtained preferably from
heart wood. Color should be uniform.
 It should be properly seasoned.
 Its freshly cut surface should smell sweet.
QUALITIES OF A GOOD TIMBER

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 Its weight should be heavy.
 It should be easily workable. It should not clog the teeth of
saw and should be capable of being easily planned.
 Timber should be tough i.e., it should be capable of resisting
shocks.
 It should be able to withstand the weathering affects.
 It should be strong enough to withstand bending, direct and
shear effects efficiently.
 A clear ringing sound should be emitted by the timber when
struck. Heavy dull sound indicates decayed timber.
 It should offer adequate fire resistance. It should be elastic.
QUALITIES OF GOOD TIMBER

18. Types of timber
Natural Industrial
Babul
Bamboo
Banyan
Neem
Mango
Teak
Pine
Palms
Veneers
Plywood
Fiberboards
Impreg timbers
Compreg timbers

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 It is easily available every where.
 Its salvage value is high.
 It can be easily transported by converting large
pieces into smaller pieces.
 Working on timber is easy. Timber constructions
can be easily repaired. Additions and alterations to
timber structures can be easily done.
 It can be easily jointed.
 In marine works, timber is considered as an ideal
material as it does not corrode. Cement and iron
structures corrode in sea water, if they are not
protected with special preservative.
ADVANTAGES OF TIMBER

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 Being light in weight, it is preferred for building
works in earth quake prone regions.
 It is an excellent material for decorative and general
use furniture. Lot of other internal decorations can
be carried out with it.
 It can with stand, shocks better than iron and
concrete.
 It is good insulator of electricity and heat.
 It is good sound absorbing material.
 Timber can be easily strengthened by attaching steel
or other material with it.
ADVANTAGES OF TIMBER

22. Advantages Disadvantages
 Easy to cut and reshape as per
desired dimensions.
 Locally available. The workers
of woodwork easily available.
 Useful to make door, window,
ventilator and furniture of
building in construction.
 Catches fire easily.
 Can be affected by termite.
 Not suitable for heavy loads
and multistoried structures.

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It can be said that there is no Engineering field, where timber is
not used one way or the other.
Uses of timber are numerous. Some of its important uses are
given as follows:
USE OF TIMBER
In form of piles, vertical posts,
beams, doors and windows.
As members of roofing trusses.
furniture-making
floors, ceiling, and partition
House post construction
Beams and rafters
Construction of bridges and boats
Furniture and instruments
Railway sleepers and packing cases
Toys and engraving work
Railway coach wagons
Formwork of cement concrete
Manufacturing of veneers and ply woods

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26. DIFFERENCE BETWEEN SOFT WOOD AND HARD
WOOD
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The classification as soft wood and hard wood have
commercial importance. The difference between soft wood and
hard wood is given below:
1. In soft wood annual rings are seen distinctly whereas in hard
wood they are indistinct.
2. The colour of soft wood is light whereas the colour of hard wood
is dark.
3. Soft woods have lesser strength in compression and shear
compared to hard woods.
4. Soft woods are light and hard woods are heavy.
5. Fire resistance of soft wood is poor compared to that of hard
wood.
6. The structure of soft wood is resinous while structure of hard
wood is close grained.

27. CROSS-SECTION OF A EXOGENEOUS TREE
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The cross-section of a exogenous tree is as shown
in the Fig. The following components are visible to
the naked eye:
1. Pith
2. Heart wood
3. Sap wood
4. Cambium layer
5. Inner bark
6. Outer bark
7. Medullar rays

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1. Pith: It is the inner most part of the tree and hence the oldest part of
exogeneous tree when the plant becomes old, the pith dies and becomes
fibrous and dark. It varies in size and shape.
2. Heart Wood: This is the portion surrounding pith. It is dark in colour
and strong. This portion is useful for various engineering purpose. This
is the dead part of wood. It consists of several annular rings.
3. Sap Wood: It is the layer next to heart wood. It denotes recent
growth and contains sap. It takes active part in the growth of trees by
allowing sap to move in upward direction. The annual rings of sap wood
are less sharply divided and are light in colour. The sap wood is also
known as alburnum.

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4. Cambium Layer: It is a thin layer of fresh sap lying between sap
wood and the inner bark. It contains sap which is not yet converted into
sap wood. If the bark is removed and cambium layer is exposed to
atmosphere, cells cease to be active and tree dies.
5. Inner Bark: It is a inner skin of tree protecting the cambium layer. It
gives protection to cambium layer.
6. Outer Bark: It is the outer skin of the tree and consists of wood
fibers. Sometimes it contains fissures and cracks.
7. Medullary Rags: These are thin radial fibres extending from pith to
cambium layer. They hold annular rings together. In some of trees they
are broken and some other they may not be prominent.

30. DEFECTS IN TIMBER
 Defects that develop after
felling the tree.
 Bow
 Cup
 Twist
 Radial shakes
 Wane
 Diagonal grains
The defects that usually occur in the timber may
be classified into two categories as follows:
 Defects that develop
during growth of the
tree.
 Shakes
 Twisted timber
 Upsets or rupture
 Knots
 Wind cracks
 Burls
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31. Defects in Timber
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Various defects which are likely to occur in timber may be of
following reasons:
 Due to natural forces
 Due to defective seasoning and conversions.
 Due to attack by fungi and insects.
Most common defects in timber are:
1. Heart Shakes
2. Star Shakes
3. Cup Shakes
4. Radial Shakes
5. Rind Galls
6. Wind Cracks
7. Knots
8. Dead Wood

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Heart Shakes:
 These are splits occurring in the centre of the tree and running
from the pith (inner most part) to wards the sap wood from the
medullary (vascular tissues) rays.
 In some timbers, these splits are hardly visible and in some
timbers these are quite permanent.
 Heart shakes are caused due to shrinkage of interior parts due to
age.
 A heart shake straight across the trunk is not a serious defect.
Medullary Rays:
 These are thin horizontal veins radiating from the pith to wards
the bark. These carry sap from outer side to inner side.

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Star Shakes:
 These are splits which radiate from the centre of the timber or
from the bark (outer side), running in the planes of medullary
rays.
 These occur due to severe frost or scorching heat of the sun.
Cup Shakes:
 These are curved splits which separate the whole or part of one
annual ring from another.
 These are caused due to the unequal growth of the timber.

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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.
Rind Galls:
 These are typical enlarged swellings and occur due to
branches cut-off.
Wind Cracks:
 These are shakes or splits on the sides of a bark of timber due
to shrinkage of exterior surface exposed to atmospheric
influence.

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Knots:
These are the roots of the small branches of the tree.
These are not harmful.
Dead Wood:
•It is the deficient in strength and weight and is the
result of trees being felled after maturity.

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42. DETERIORATION OF TIMBER (OR) DECAY OF TIMBER:
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There are so many agencies which may cause decay of timber.
But there are three main harmful agencies which cause timber
decay.
1.Decay or Rot: Decay or rot of timber is the result of the
activity of various bacteria and fungi, which utilize various
portions of timber as food; they require both oxygen and excess
moisture. Hence timber having moisture content below 25 % will
not rot easily.
2.Insects: There are so many insects which attack the wood, out
of them termites (white ants) are the main insects which are very
dangerous for timber. Termites of one class live under ground
and eat wood and forms tubes or tunnels inside it.
3.Fire: Fire is also the damaging factor for timber. As timber has
tendency to burn, so fire can damage it easily.

43. PRESERVATION OF TIMBER
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It means protecting timber from attack of fungi and
insects so that its life is increased.
TIMBER PRESERVATIVES:
There are three main classes of timber preservatives.
 Oily substances insoluble in water
 Water soluble salts
 Special paints to save timber from fire

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Oily substances insoluble in water:
1. Coal tar oil is the best known and widely used preservative
material of this class.
2. It is obtained during the destructive distillation of bituminous
coal. It is available in many grades and types.
3. It has high degree of penetration.
4. It has highly toxic effect to wood destroying fungi.
5. The coating of tar protects the timber from the attack of fungi
and insects.
6. It is a cheapest way of protecting timber.
7. Main disadvantage Appearance is not good after tar is applied.

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Water soluble salts:
1. These are the preservatives made by dissolving salts in water.
2. The salts used are copper sulphate, masonry chloride, zinc
chloride and sodium fluoride.
3. Zinc chloride is the most extensively used preservative of this
type.
4. It is clean and odourless.
5. After treating the timber with these chemical salt paints and
varnishes can be applied to get good appearance.
6. After treating the timber with these chemical salt paints and
varnishes can be applied to get good appearance.

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Special paints to save timber from fire:
Following paints are used to save timber from fire. Diammonium
phosphate, Mono ammonium phosphate, Mono magnesium
phosphate, Phosphoric acid.
Creosote oil treatment:
1. Creosote oil is obtained by distillation of coal tar.
2. The seasoned timber is kept in an air tight chamber and air is
exhausted.
3. Then creosote oil is pumped into the chamber at a pressure of
0.8 to 1.0 N/mm2 at a temperature of 50°C.
4. After 1 to 2 hours timber is taken out of the chamber.

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ASCO Treatment:
1. This preservative is developed by the Forest Research Institute,
Dehradun.
2. It consists of 1 part by weight of hydrated arsenic pent-oxide (As2O5,
2H2O), 3 parts by weight of copper sulphate(CuSO4⋅5 H2O) and 4 parts
by weight of potassium dichromate (K2Cr2O7) or sodium dichromate
(Na2Cr2O7⋅2 H2O).
3. This preservative is available in powder form.
4. By mixing six parts of this powder with 100 parts of water, the solution
is prepared.
5. The solution is then sprayed over the surface of timber.
6. This treatment prevents attack from termites.
7. The surface may be painted to get desired appearance.

48. Plywood
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 Produced by gluing many layers of split wood
together.
 The grains are arranged alternatively to eliminate
distortion.
 The plywood is a very good modern construction
material whose quality depends on type of wood
used, glue used and pressure of steam used in
gluing.

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Wood can be cut into many shapes.
a) Plank: The thickness is small when compared to its width.
t
t < < B
B
Plank
b) Beams: Width and thickness dimensions are almost same.
Beams

50. Shapes of Wood Contd: Block
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 c) Blocks: Very thick eg. 25 x 25 mm(width-
depth) or 20 x 25 mm or 30 x 30 mm
 BLOCK
Many grades of wood exist depending on the
strength.
BLOCK

51. METALS
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 These are man-made materials whose
properties are known. The most widely used
metal is steel.
Steel:
Steel is very strong, highly durable,
resistant against weather, fire and insects and
possesses almost all good characteristics.
 Steel is used in reinforcement in concrete,
gates, windows, roof trusses, steel sheets for
partitions and tanks etc.

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53. (Synthetic Materials)
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 a) Asbestos Cement: Used for making roof
sheets, drain pipes and accessories. It is also
used for partitions and ceilings.
 b) Plastics: used in water supply and sanitary
systems. Also electric fittings.
 c) Ceramics, fibre glass etc. are new materials
used in some restricted areas.

54. PAINT & VARNISHES
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 The paints are coating of fluid materils and they are
applied over the surface of timber and metal.
 The varnishes are transprent or nearly solution of
resineous materials & they re applies over the painted
surfaces.

55. TYPES OF PAINTS
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 Aluminium paints
 Cement paint
 Asbestos paint
 Bituminous paint
 Emulsion paint
 Oil paint
 Plastic paint
 Synthetic ruber

56. PROPERTIES OF PAINT & VARNISH
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 They are available in wide range of variety.
 They are speaded & strached as a layer on base by
brushes.
 They are transparent
 They provide shine on old & new wood work.

57. REQUIREMENT OF PAINT & VARNISHES
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 The paints applied on a surface should dry within 24
hours.
 The paint should neither crack nor shrink after drying.
 The paint should have an attractive appearance.
 The colour of varnish should not develop cracks on
drying.
 The varnish should adopt or accommodate to the
expansion & contration of wood due to temperature
varations.