WOOD

INTERIOR MATERIAL & TECHNOLOGY- 1
S E M 01
AAERT _SCHOOL OF INTERIOR DESIGN
S.E.M.- 01

Wood
Task – name 10 objects made of wood that is in close proximity to you.

Wood
Can you name any types of wood?
pine, oak, ash, teak, mahogany, maple, rose wood, beech, Babul,
Bamboo, walnut, cherry, zebrawood, balsa, Deodar, Sal…….
pine oak beech walnut maple zebrawood mahogany ash
Can you think of words that describe wood?
warm, smooth, strong, flexible, strong, hard, soft, rough, ….
warm, smooth, strong, flexible, strong, hard, soft, rough, ….

Introduction
• Derived from the word timberian , that means to build
• Denotes wood which is suitable for building or carpentry.
• Three terms to be known in connection to the timber.
– Converted timber: sawn and cut into suitable commercial sizes.Converted timber: sawn and cut into suitable commercial sizes.
– Rough Timber: obtained after felling a tree
– Standing Timber: Timber contained in living tree
V l bl ti• Valuable properties:
» Low heat conductivity
» Ability to mechanical working
» Small bulk density
» High Strength
• Drawbacks• Drawbacks
» Decay
» Inflammability
» Fluctuation in properties due to changes in moisture

Classification
Trees
Exogenous
They increase in bulk by growing outward
and distinct consecutive rings are formed
every year in the horizontal section of the
Endogenous
They grow inwards and fibrous mass
is seen in their longitudinal section
e.g. bamboo, cane , palmy y
tree
g , , p
Conifers DeciduousConifers
-Also Known as ever green trees.
-Leaves do not fall till new one are
grown.
Deciduous
They increase in bulk by growing outward
and distinct consecutive rings are formed
every year in the horizontal section of the
treetree
Soft Wood
-Light colored
Resinous
Hard Wood
• Close grained
•Strong-Resinous
-Light in weight and weak
-Poor fire resistant
-Strong in direct pull and week for resisting
thrust or shear
Strong
•Heavy
•Dark colored
•Durable
•Non resinous
thrust or shear
-Eg. chir, devdar, fir, kail, pine spruce etc
Non resinous
•Do not show distinct annual rings
•Eg. Babul, mahogany, oak, sal , teak rose wood etc

Xylem
Th d ti
Sapwood
•The younger •The woody tissue
of a tree that
provides support
and conducts water
d i l
•The younger,
softer living portion
of wood between
the cambium and
heartwood and mineral
nutrients upward
from the roots
heartwood.
•Usually lighter in
color, more
permeable and less
durabledurable.
Annual Ring
Inner Bark
•A Layer of tissue
that carries food
g
•A Concentric layer
of wood produced
during a single
year’s growth of
that carries food
from the leaves to
the growing parts of
the tree.
•Also called year s growth of
temperate tree
•It is also known as
Growth ring.
•Also called
Phloem

Pith
Th i t
Bark
•The Tough •The innermost
central portion of a
tree is called pith or
medulla.
V i i i d
•The Tough
external covering of
a woody stem,
branch or root,
composed of a •Varies in size and
shape from tree to
tree.
•It is a soft part
b t hi h fi t
composed of a
living inner layer
called phloem and
an outer bark of
corky dead tissue about which first
growth takes place
in a newly formed
stem
corky, dead tissue.
Heartwood
•The older harder•The older harder ,
inactive core of a
tree, usually darker
denser and more
durable than thedurable than the
surrounding sap
wood
•They are the inner
annual rings
annual rings
•Imparts rigidity.

Elements of tree

Elements of tree
PITHPITH
CAMBIUM
INNER BARK
OUTER BARK
INNER BARK

Identifications of Timber
• General Properties
Color a darker color in wood indicates greater durabilityColor – 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 causedy
by harder bodies.
Density – densest woods are generally the strongest.
G i D di th t l li t th i bGrain - Depending on the actual alignment, the grain may be
straight, spiral, interlocked, wavy or irregular.
Spiral Grainp
Interlocked Grain
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.

Identifications of Timber
• Workability- the relative case in which wood is shaped cut andWorkability 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
surfacesurface.
• Moisture content- is a percentage of the mass of water over the mass
of wood fiber 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

Mechanical Properties
• Tensile Strength – Timber is stronger in tension along the rain but it’s
quite difficult to determine this because of the difficulties in conducting
test.
• Compressive Strength – The strength along the grain is important for
columns, props, and post.columns, props, and post.
• Shear Strength – Shear strength is important in the case of the beam
and slabs.
B di S h Thi f h h f h i b b• Bending Strength– This refers as the strength of the timber as a beam.
• Cleavability – High resistance for cleavage is important for nailing and
screwing while low splitting strength is important for used as firewood.g p g g p
• Torsion Strength – is used to determine the torsion strength of the
timber and the specimen is loaded up to failure.
H d i i t t i f ti b f i bl k fl i• Hardness – is important in case of timber for paving blocks flooring
bearings and other similar purposes.
• Stiffness - This property is important to determine the deflection of a
p p y p
timber under a load.

DEFECTS AND DECAY IN TIMBER
• CENTRE HEART/HEART SHAKES
• BOW
• KNOTS
• CUPPING

Defects in timber
Timber is a natural material that is prone to defects.
One of these is the tendency to split if it is put
under stress from rapid drying or de-lamination of
the growth ringsthe growth rings.
These defects are all known as ‘Shakes’
Upsets- are clipping or buckling of fibers caused
by crushing of fibers when the trunk is felled
violently over a rocky surface.
Wind Cracks- are shakes on the outside of a logWind Cracks are shakes on the outside of a log
due to the shrinkage of the exterior surface caused
by the atmospheric influences.

KNOTS
Knots - are dark, hard pieces occurring as signs of branches broken or
cut offcut off.

Shakes
•Shakes- or cracks are caused by the rupture of tissues resulting in partial
or complete separation of the fibers along the grain.
Star ShakesStar Shakes
Heart Shakes
Cups Shakesp
Ring Shakes
Radial Shakes

BOW
• Bow- a curvature of the timber in the direction of its length. This defects
are Due to Seasoning.g

CUPPING DEFECTS
• Cup- a curvature in the transverse direction of the timber. This defects
also are Due to Seasoning.g

Wood
TIMBER is the general name for wood materialsTIMBER is the general name for wood materials.
There are 3 main types of timber:
HARDWOOD• HARDWOOD
• SOFTWOOD
• MANUFACTURED BOARD

Hardwood
This type of timber is produced from broad leafThis type of timber is produced from broad leaf
trees that lose their leaves in winter – a
deciduous tree. The photograph opposite is of
an oak tree which grows in this countryan oak tree which grows in this country.
U O k i h d d d i d t kUses - Oak is a hardwood and is used to make
expensive furniture/flooring and strong framed
structures.
The term hardwood does not mean that the
timber is hard. For example balsa is used for
modelling, it is a hard wood but it is one of the
softest timbers to work with.
Model aircraft made
from balsa

Hardwood
Mahogany – reddish in colour alwaysMahogany – reddish in colour, always
looks good when varnished or waxed.
Beech – creamy pinkish colour, its
close grain makes it very suitable forg y
kitchen utensils, as water does not
have too great an effect on it.
Task – Can you think of othery
uses of wood products in the
kitchen.

Softwood
This type of timber is produced from trees that
Softwood
yp p
do not lose their leaves (coniferous).
Leaves are easily
identified as
being thin and
narrow.
Softwood trees grow much quicker than the
hardwood ones, they are therefore cheaper to
buy and far more available Softwood is usedbuy and far more available. Softwood is used
for construction of houses and furniture, and
outdoor uses such as fencing.
The term softwood does not mean that the
timber is soft as pitch pine is one of the mosttimber is soft , as pitch pine is one of the most
difficult timbers to work with, yet is a member of
this group

Uses of soft woods
Furniture Building
Construction
Packaging

Manufactured Products Of Timber
These are manmade boards, which are made by
gluing wood layers or wood fibers together.
Examples of manufactured boards are:
Plywood is a widely used manufactured timberPlywood is a widely used manufactured timber.
Can you think of advantages and disadvantages of
using plywood?using plywood?
The photograph opposite shows MDF sheets. What does
MDF t d f ? A th ht di it ?MDF stand for ? Any thoughts regarding its use ?
Manufactured board is mainly used for kitchen and
bedroom furniture and shelving.

• VENEERS
• LAMINATES
• PLYWOOD
• PARTICLE BOARD
• FIBER BOARDS• FIBER BOARDS
• BATTEN BOARDS : BLOCK BOARDS AND LAMINATED BOARDS
• VENEERS - Thin sheet of wood, 0.4 mm to 0.6 mm in
thickness obtained by different knife cutting process.
• PLYWOOD - is made by gluing together veneers.
• It has a good strength both across as well as• It has a good strength both across as well as
along the grain.
• Plywood has better splitting resistance due to grains in adjacent layers
y p g g j y
running at the right angle and nailing and screwing even closed to the
edges in safe.

• PLYWOOD
• Can easily be bending to a curvature limited by
h il d h i h f hthe tensile and the compressive strength of the
other plies.
• The face piles made at different heartwoodsp
show great aesthetic variety in grain pattern and
color.
• PARTICLE BOARDS is a board manufactured• PARTICLE BOARDS - is a board manufactured
from particles of wood or other cellulose
materials.
• BATTEN BOARD – it is a board having a core
made up of strips of wood usually 8 cm wide
each laid separately or glued or otherwise joinedp y g j
to form a slab.
• BLOCK BOARD – these are boards having a
core made up strips of wood each not exceeding
core made up strips of wood each not exceeding
25 mm.

carve it…
you can ……
layer it …
y
Bend it …..
slot it together it …..
turn it …..

Things that attack timber

Decay of Timber
• Termites
• Beetles
AAERT _SCHOOL OF INTERIOR DESIGNFlour like powder

Timber Seasoning
• Removal of moisture from timber so as to be in equilibrium with
moisture in surrounding atmospheric conditions where timber ismoisture in surrounding atmospheric conditions, where timber is
likely to be used, is called as seasoning.
• When timber is first felled it is known as green timber and has a very high
moisture content – approx 50%
• Before it can be used it must be dried• Before it can be used it must be dried
• If this process is not controlled properly defects can occur that can ruin
good timber
• Aim of seasoning is to dry out the wood to a suitable moisture content of
22% or less

OBJECTIVES OF SEASONING
• Seasoning improves following properties:
– Strengthg
– Durability
– Working qualities including polishing, painting, and gluing
– Resistance to attack of insects, fungusResistance to attack of insects, fungus
• Proper seasoning reduces tendency to split, shrink and warp.
• Seasoning reduces weight of timber and is easy to handle.
• Timber becomes fit to receive preservative & to finish like• Timber becomes fit to receive preservative & to finish like
preservatives, paints, and varnish treatment.
• To reduce weight and minimize cost of transportation.
• To make the timber burn readily if used as a fuel• To make the timber burn readily, if used as a fuel.

TYPES OF SEASONING
• Natural Seasoning - is a slow process and the reduction in moisture
content to the desired level may not be attainable by air seasoningy y g
alone.
• Artificial or Kiln Seasoning - is a quicker method of seasoning timber t
the desired moisture content under highly controlled conditionsthe desired moisture content under highly controlled conditions.
• Electrical Seasoning - in this method high frequency alternate electric
current is passed through timber.
• Chemical Seasoning - If the outer layers of timbers are treated with
such solutions, the vapor pressure of the outer layers is reduced and a
vapor pressure gradient is set up.vapor pressure gradient is set up.

ADVANTAGES OF TIMBER
• In terms of specific strength 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
connectorsconnectors.
• 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• Durability of timber can be very high, if properly seasoned and
preserved.
• Timber constructions are light in weight.
• For aesthetic and decorative appearance.

USES OF TIMBER AS A BUILDING MATERIAL
BEAMS• BEAMS
• TRUSSES
RAFTERS• RAFTERS
• JOISTS IN FLOORS
DOORS FRAME AND SHUTTERS• DOORS FRAME AND SHUTTERS
• WINDOWS FRAME AND SHUTTERS
STAIR CASES• STAIR CASES
• POLES
PILES• PILES
• COLUMNS

Before we use wood, what should we think about ?
Wood - sustainability considerations.
A tree absorbs CO2 as it grows and stores the
carbon as wood. When it reaches maturity it
stops absorbing extra carbon. Eventually, if not
cutdown, it will die and gradually give off CO2cutdown, it will die and gradually give off CO2
as it rots.
If it is cut down and the wood is used for products
such as furniture or buildings this locks
up the carbon in the timber for the lifetime of
the productthe product.
If the tree is replaced the new tree will start
absorbing more CO2.absorbing more CO2.

Before we use wood, what should we think about?
How does using wood affectg
Climate Change?
lid ti bIf you use solid timber there is very little
processing.
Energy is used to plant and then fellgy p
the trees, move them, saw and plane
the timber and then transport it.
The further it is transported the more
energy is used.

Manufactured boards use
more energy to produce.
They can use the waste fromThey can use the waste from
milling solid timber.
They mostly use adhesives,
and the formaldehyde that is
used in MDF is a health risk.

Other ecological impacts
Some tropical hardwoods have hugeSome tropical hardwoods have huge
impacts. Mahogany trees grow in amongst
a variety of other trees and plants. Cutting
down the mahogany causes the destructiondown the mahogany causes the destruction
of a whole area of rainforest which cannot
regrow easily.
Does it’s use harm other people?
If we add to Climate Change that affects
e er one in the World b t partic larl theeveryone in the World but particularly the
poor who are most affected by drought and
flooding. If we destroy areas of rainforest
that affects the lives of the people who livethat affects the lives of the people who live
in the forest.

Can we keep on using as much as
lik ?we like?
The planet has a limited amount of
land to grow food and trees so there is
a limit to the amount of timber we
can use. However, the amount that
is used in the production of the paperis used in the production of the paper
that comes into the average house
each year will be a far bigger impact
than the timber in your school projectthan the timber in your school project.
But the products we do design and
make should be well made, so they
b fcan be used for a number of
years.

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