3. •Construction material is any material which is
used for construction purposes.
•Many naturally occurring substances have been
used to construct buildings :
oClay
oRocks
oSand
oWood
oTwigs
oLeaves
Clay
Stone
Sand
Twig
4. WHAT IS WOOD
•Wood is a porous and
fibrous structural tissue
found in the stems and
roots of trees and
other woody plants
•It has been used for
thousands of years for
both fuel and as a
construction material.
•It is an organic
material, a natural
composite of cellulose fi
bers (which are strong in
tension) embedded in
a matrix of lignin which
resists compression.
11. •Hardwood is wood from dicot angios
perm trees
•The term may also be used for the
trees from which the wood is derived;
these are usually broad-leaved.
•In temperate and boreal latitudes th
ey are mostly deciduous, but
in tropics and subtropics mostly everg
reen
•Hardwoods are not necessarily
harder than softwoods
12. Characteristics
•Hardwoods have a more complex
structure than softwoods
•Dark in colour
•Expensive
•Slower growth rate
•Higher density
•Heavy in weight
•More fire resistant than soft wood
•Strong in compression and
tension
13. Examples - Oak
•Light in colour
•Heavy
•Ring porous
•Open grain
•Hard to work with.
•When treated it looks classy and
elegant
14.
15. Examples - Maple
•Maple is so hard and resistant to
shocks that it is often used for
bowling alley floors.
•Its diffuse evenly sized pores
give the wood a fine texture and
even grain.
•Maple that has a curly grain is
often used for violin backs.
•Burls, leaf figure, and birds-eye
figures found in maple are used
extensively for veneers.
16.
17. Examples - Mahogany
• An easy to work wood
•reddish brown in colour
•Expensive
•Strong
• poorly defined annual rings
•may display stripe, ribbon,
broken stripe, rope, ripple, mottle,
fiddle back or blister figures
•excellent carving wood and
finishes well
18.
19. Examples - Cherry
• hard
•Strong
•Light to red-brown wood
•Resists warping and checking
•Easy to carve and polish
20.
21. Examples – Rubber wood
• light colour
•Medium density
•Usually from the tree of rubber
plantation
•Advertised as eco-friendly wood
oBecause It is not grown
specially for timber but instead
have timber as by product
22.
23. •Softwood is wood from gymnosperm
trees such as conifers
•Softwood is the source of about 80%
of the world's production of timber
•Softwoods are not necessarily softer
than hardwoods
•The woods of long leaf pine, douglas
fir, and yew are much harder in the
mechanical sense than
several hardwoods
24. Characteristics
•Cheap comparative to hard wood
•Faster rate of growth
•Lower density
•Softer than hardwood
•Light in colour
•Light in weight
•Poor fire resistant
•Strength in tension but week in
sheer
25. Examples - Ash
•Hardwoods have a more complex
structure than softwoods
•Dark in colour
•Expensive
•Slower growth rate
•Higher density
•Heavy in weight
•More fire resistant than soft wood
•Strong in compression and
tension
26.
27. Examples - Pine
• soft
•White or pale yellow in colour
•Light weight
•Straight grains
•Lack figures
•Resists shrinking and swelling
•knotty
28.
29. Examples -Cedar
• Knotty soft wood
•Red brown colour with light
steaks
•Aromatic and moth repellant
•Popular wood for lining drawers,
chests and boxes
• Brittle wood
30.
31. Examples –Red wood
•The best quality redwood comes
from the heartwood which is
resistant to deterioration due to
sunlight, moisture and insects
•Redwood burls have a "cluster of
eyes" figure.
•They are rare and valuable.
32.
33.
34. •Reduces moisture content of wood
•There are two main reasons :
i. Woodworking: when wood is used as a construction material,
whether as a structural support in a building or in wood
working objects, it will absorb or desorb moisture until it is in
equilibrium with its surroundings. Equilibration (usually drying)
causes unequal shrinkage in the wood, and can cause damage to
the wood if equilibration occurs too rapidly. The equilibration must
be controlled to prevent damage to the wood.
ii. Wood burning: when wood is burned, it is usually best to dry it first.
37. •Also called composite wood, man-made wood, or
manufactured board
•Includes a range of
derivative wood products which are manufactured by binding
or fixing the strands, particles, fibers, or veneers or boards
of wood, together with
adhesives, or other methods of fixation to form composite
materials
•Engineered wood products are used in a variety of
applications, from home construction to commercial buildings
to industrial products.
38. Plywood
• Plywood is a sheet material manufactured
from thin layers or "plies" of wood
veneer that are glued together with adjacent
layers having their wood grain rotated up to
90 degrees to one another
•This alternation of the grain is called cross-
graining and has several important benefits:
o it reduces the tendency of wood to split
when nailed at the edges
o It reduces expansion and shrinkage,
providing improved dimensional stability
oIt makes the strength of the panel
consistent across all directions.
39. Block board
• Blockboard is a wood based panel, made up
of a core of softwood strips glued together
•The strips may be up to about 28mm wide
and are placed edge to edge and sandwiched
between veneers of softwood, hardwood or
thin MDF or particleboard, glued under high
pressure
•The internal strips are generally made of light
weight poplar wood or spruce
•To achieve maximum strength, it is important
to ensure that the core runs lengthways
•has very good screw holding
•it has a good resistance to warping.
40. Veneers
• veneer refers to thin slices of wood,
usually thinner than 3 mm (1/8 inch),
that typically are glued onto core
panels
•Veneer is obtained either by "peeling"
the trunk of a tree or by slicing large
rectangular blocks of wood known as
flitches
• The appearance of
the grain and figure in wood comes
from slicing through the growth rings of
a tree and depends upon the angle at
which the wood is sliced
41. Laminates
• Lamination is the technique of
manufacturing a material in multiple layers, so
that the composite material achieves
improved strength, stability, sound insulation,
appearance or other properties from the use
of differing materials
•A laminate is usually permanently assembled
by heat, pressure, welding, or adhesives
42. Particle board
• also known as chipboard
•manufactured
from wood chips, sawmill shavings,
or even sawdust, and a
synthetic resin or other suitable
binder, which is pressed
and extruded
•It is a composite material
43. Medium Density Fiber board
• made by breaking down
hardwood or softwood residuals
into wood fibres, often in
a delibrator, combining it
with wax and a resin binder, and
forming panels by applying
high temperature and pressure
•MDF is generally denser
than plywood
•It is made up of separated fibres
•stronger and much denser
than particle board
44. High Density Fiber board
• also called hardboard
• made out of exploded wood fibres
that have been highly
compressed
• It differs from particle board in that
the bonding of the wood fibres
requires no additional materials,
although resin is often added
• Unlike particle board, it will not split
or crack
