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Building Technology 1
WOOD
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WOOD
Fibrous substance which composes the trunkand branches of a tree that lies between thepitch and the bark.
defined as the lignified water conducting,strengthening and storage tissues of branches,
stem and roots of trees.
wood is known as xylem.
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PARTS OF WOOD
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PARTS OF WOOD
heartwood Hard dark-colored wood
layer made of deadsapwood; it encircles
the pith and supportsthe trunk and branches.
pith
Central part of the
trunk, composed of softtissue that containsnutrients essential forsapling growth.
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PARTS OF WOOD
bark Trees external protective
layer; its texture and color
vary depending on the
species.Phloem
Tissue located immediately
below the bark, whose main
function is to transport sap
transformed by
photosynthesis from the
leaves throughout the rest of
the tree.
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PARTS OF WOODcambium
Growth tissue that
simultaneously produces the
external phloem and the
internal sapwood, therebyenabling the tree to increase in
diameter.
sapwood
Relatively new layer of woodthat is generally pale in color; it
transports raw sap, composed
of water and nutrient minerals,
from the roots to the leaves.
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PARTS OF WOODannual ring
Each of the concentric circles
representing the layer of
wood produced in one year;
the age of the tree can bedetermined by the number of
rings.
wood ray
Conduit connecting the pith to
the core and circulating
nutrients horizontally within
the trunk.
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Properties of Wood as a Building
Material
Strong material
Durable
Light in weight
Ease of working and fastening
With artistic and natural beauty
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Advantages of Wood as Building
Material
In proportion to weight, wood is stronger than
other materials.
Wood is easily worked out with tools and
fabricated into many shapes, sizes and design.
Wood is excellent non-conductor of heat. It is
warm in winter and cool in summer.
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Advantages of Wood as Building
Material
It is abundant in many shapes, color, sizes, and
as renewable resources.
The use of timber connectors in wide trusses
and spans generally permit the use of small
wood members.
In terms of value, wood does not deteriorate if
properly handled and protected.
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Advantages of Wood as Building
Material
It is not readily affected by changing styles.
It has prompt resale value.
Neither heat nor cold or climate changes
would seriously affect the physical propertiesof wood.
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Physical Properties of Wood
1. Strength- ability of wood in resisting stress andstrain.
Strength of different wood varies in the following
manner: Resistant to compression
Stiffness or ability to resist bending stress
Strength in tension or ability to resist lengthwisestress
Shearing strength or ability of the fibers to resistrupture along or across the grain
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Physical Properties of Wood
2. Knots and other defects in wood- affects thestrength more particularly the size, character andlocation of the knots or defects.
3. Weight-heavy woods are generally stronger thanlighter wood.
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Physical Properties of Wood
4. Hardness-expressed as resistance to indentationor to the saw or axe across the grain.
-generally dependent on the weight of the wood,
structural elements and degree of seasoning.
5. Cleavability-resistance of wood to split along thegrains
6.Flexibility-the moisture content of the woodinfluences the flexibility to a considerable degree.
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Physical Properties of Wood
7. Toughness-refers to the combined strength,shock resistance and pliability or flexibility of the
wood.
8. Durability-ability to resist decay ; length of its lifeunder a given condition; resistance of the woodto the influence of mechanical wear.
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Classification of Wood
Mode of Growth:
Exogenous- outward growing trees mostpreferred for lumbering
Indigenous- inside growing trees; lesspreferred for lumbering because the center
core of the log is soft and brittle in character.
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Classification of Wood
Density- mass & volume of the wood
1. Softwood- known as conifers or evergreen
1.1 Conifers: Tree that usually retains its
needle- or scalelike leaves all winter long; itbears cones, hence its name, and produces a
sticky sap known as resin.
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Classification of Wood
1.2 Evergreen- having foliage that remains
green and functional throughout the year
or through more than one growing season
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Classification of Wood
Softwood
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Classification of Wood
Softwood
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Classification of Wood
2. Hardwood-generally deciduous with broad
leaves
Deciduous- shredding leaves annually or at
the end of a growing season.
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Classification of Wood
Hardwood
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Classification of Wood
Hardwood
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Classification of Wood
Hardwood
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Classification of Wood
Leaves:
Needle shape
Broad shape
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Classification of Wood
Shade or color of wood:
White Red
Yellow
Brown
Orange
Black, etc.
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Classification of Wood
Grain:
Straight grain
Cross grain
Fine grain
Coarse grain
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Classification of Wood
Grain
When you cut a board across the grain
(perpendicular to the grain direction and the
growth rings), you reveal end grain.
Cut wood parallel to the grain direction and
tangent to the growth rings, and youll
seeplain grain(also called tangentialor flat
grain).
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Classification of Wood
Grain
Cut it parallel to the grain direction but
through the radius of the growth rings to
see quarter grain (also referred to
as radialgrain).
Both flat grain and quarter grain are
sometimes called long grain.
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Classification of Wood
Grain
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Classification of Wood
Nature of the Surface when sawed:
Plain
Grained
Figured or marked
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Classification of Wood
Figured
Wood grain isnt always straight and even. The
longitudinal and ray cells sometimes grow in
unusual patterns, many of which are strikinglybeautiful. These are known asfigured grain.
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Classification of Wood
Figured A few wood species, such
as white oak, haveespecially prominent rays.When quartersawn, these
produce silver grain.
Crotch figure, such as thiswalnut crotch, is cut from
the part of a tree wherethe trunk divides intosmaller limbs andbranches.
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Classification of Wood
Figured
Curly grainoccurs whenthe longitudinal cells growin waves. This occurs inmany species but isespecially striking inmaple.
Birds eyeslike those inthis maple are caused by
small dimples in the layersof cells. These are thoughtto be caused by a fungusthat affects the growth ofthe longitudinal cells.
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Classification of Wood
Figured
Larger dimples resultin quilted figure, like thequilting in this soft maple.This, too, is the result of afungus
The longitudinal cells ofcertain species, such asmahogany, sometimes
spiral around the trunk,reversing direction everyfew growth rings. Thiscreates ribbon figure.
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Classification of Wood
Figured
Sometimes a tree produces a large growth on theside of the trunk or a branch. The cells seem toswirl around each other inside these growths.When sliced, these produce a burl figuresuch asthis elm burl.
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Texture & Pattern
TEXTURE AND PATTERN
The size, type, and arrangement of the wood
cells differ with the species, and this also
affects the appearance of the grain.The texture of the wood is determined by the
relative size of the longitudinal cells. Wood
species with large cells are said to havea coarse texture, while those with smaller
cells have afine texture.
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Texture & Pattern
The pores in ring-porous hardwoods such as
red oak create a strong grain pattern
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Texture & Pattern
The pores in ring-diffuse hardwoods like
mahogany are more evenly distributed and the
grain pattern is less distinct
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Texture & Pattern
Softwoods such as yellow pine have no pores. The
grain pattern is due to the color difference between
the springwood and the summerwood.
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Changing Shape
Because of the difference intangential and radial movement,
boards change shape as they
expand and contract. The way
in which they change depends
on how they are cut from thetree.
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Changing Shape
The difference in tangential and radialmovement has other important
consequences. Depending on how its cut
from the tree, a board may change shape as it
dries:
If the annual rings run side to side in square
stock, the stock will shrink to a rectangle.
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Changing Shape
If the rings run diagonally from corner to
corner, the stock will become diamond-
shaped.
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Changing Shape
Round stock becomes oval as the tangential
diameter shrinks more than the radial
diameter.
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Changing Shape
Plain-sawn lumber tends to cup in the
opposite direction of the growth rings because
the outside face (the face farthest from the
pith) shrinks a little faster than the inside face.
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Changing Shape
In quartersawn lumber, both faces shrink
equally and the board remains flat.
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Preparation of Wood
1. Logging- harvesting of the tree crops
consisting a sequence of operations such as:
Cutting of the tree
Skidding- when logs are moved to an assembly
area loaded to transport equipment then
carried out of the forest to the sawmill.
Bucking- process of sawing into smaller pieces
after the removal of branches.
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Preparation of Wood
Skidded-when the log is dragged and carrieddown to an assembly area.
Yarded-when logs are delivered through the
cable or a helium filled balloon. Lumbering-operation performed in preparing
wood for commercial purposes. It involveslogging which is the process of felling trees,hauling and delivery to the sawmill.
Sawing
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Methods of log sawing employed
1. Plain or Bastard sawing- by cutting the logs
entirely though the diameter with a parallel
chord tangential to the annual rings.
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Methods of log sawing employed
2. Quarter or rift sawing- categorized into four
methods of sawing:
Radial method
Tangential method
Quarter tangential
Combined radial &tangential
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Methods of log sawing employed
Live saw(This is sometimes called sawing through andthrough.) Live sawing produces much wider boards
than other methods, and these boards show mostly
mixed grain flat grain near the center of the face
and quarter grain near the edges.
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Definition of Terms
Surfaced or dressed lumber- is a planed
lumber having at least one smooth side.
S2s & s4s- planed or dressed lumber of which
the number connotes the smooth sides. S2s
means smooth on two sides & s4s on four
sides.
Slab- kind of rough lumber cut tangent to theannual rings of wood running the full length of
the log containing at least one flat surface.
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Definition of Terms
Timber- is a piece of lumber five inches or
larger in its smallest dimension.
Plank- is a wide piece of lumber from 2 to 5
inches thick.
Board-is a piece of lumber less than 1 thick
and at least 4 inches wide.
Flitch- is a thick piece of lumber.
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Definition of Terms
Fine grain- when annual rings are small, the
grain marking which separates the adjacent
rings is said to be fine grain. When large, it is
called Coarse-grained.
Straight grained- when the direction of the
wood fibers are nearly parallel with the sides
and edges of the board.
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Definition of Terms
Lumber- is the term applied to wood after it wassawed or sliced into boards, planks, sticks, etc. forcommercial purposes.
Strips. Lumber less than 2 thick and less than 8wide.
Board Lumber. Pieces less than 2 thick and atleast 8 wide.
Dimension Lumber. Pieces more than 2 and lessthan 5 in any dimension.
Timbers. Pieces 5 or more on the smallest
dimension
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Definition of Terms
Rough lumber- is the term applied to newly
sawed lumber.
Silviculture- is the process of growing timber
crops of a better and more valuable species as
rapidly as possible through scientific forestry.
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Defects in Wood
1. Abnormal growth Heart shakesare radial cracks originating at the
heart of the logs.
Wind shakes or Cup shakes- cracks or breaksacross the annual rings of timber during itsgrowth caused by excessive bending of the treedue to wind.
Star shakes- composed of several heart shakes
radiating from the center of the log in a star-likemanner.
Knots- usually occur at the starting point of alimb or branch of the wood.
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Defects in Wood
Dry-rot-is the presence of moisture in
seasoned wood caused by fungi.
Wet rot-usually takes place sometime in the
growth of trees caused by water saturation.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Bow
A curve along the face of a board that usually
runs from end to end. Usually resulting from
imporper storage.
Defects in Wood
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Defects in Wood
(Man Made Defects)Check
A crack in the wood structure of a piece,
usually running lengthwise. Checks are usually
restricted to the end of a board and do not
penetrate as far as the opposite side of
a piece of sawn timber. This is easily overcome
by removing the endpieces of the board.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Crook
Warping along the edge from one end to the
other. This is most common in wood that was
cut from the centre of the tree near the pith.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Cup
Warping along the face of a board across the
width of the board. This defect is most
common of plain-sawn lumber.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Shake
Separation of grain between the growth rings, often
extending along the board's face and sometimes
below its surface.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Split
A longitudinal separation of the fibers which
extends to the opposite face of a piece of
sawn timber.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Twist
Warping in lumber where the ends twist in
opposite directions. Probably the worst of the
defects. This board is unworkable unless it iscut into smaller pieces and flattened with a
jointer.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Wane
The presence of bark or absence of wood on
corners of a piece of lumber.
Defects in Wood
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Defects in Wood
(Man Made Defects)
Machine Burn Discoloration of the wood due to overheating caused
by friction, and either scorching the wood or the
resins within it. Machine burn is caused by stopping
or not feeding the wood across the blades at the
correct rate of speed. Although species like cherry,
pine, or walnut are more susceptible than others,
machine burn can almost always be prevented by
using sharp blades and correct
feed rates.
Defects in Wood
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Defects in Wood
(Natural Defects)
Worm hole- This is caused by
insects boring through the wood.
Defects in Wood
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Defects in Wood
(Natural Defects)Blue Stain
A discoloration that penetrates the wood fibre. It
can be any colour other than the natural colour of
the piece in which it is found. It is classed as light,medium or heavy and is generally blue or brown.
Defects in Wood
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Defects in Wood
(Natural Defects)
Spalt
Typically found in dead trees, spalting is any form of
wood discoloration caused by fungi. There are three
types of spalting that are typically incorporated intowoodworking as design elements, pigmentation (or
sapstain), white rot, and zone lines.
Defects in Wood
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Defects in Wood
(Natural Defects)Pitch
An accumulation of resinous material on the surface
or in pockets below the surface of wood. Also called
gum or sap.
Defects in Wood
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Defects in Wood
(Knot)
Dead or Loose
Knot having annual rings not intergrown with
those of the surrounding wood.
This is caused by a dead branch that was notfully integrated into the tree before it was cut
down.
Defects in Wood
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Defects in Wood
(Knot)
Tight Knot- a knot held firmly in
place by growth or position
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Seasoning of wood
Seasoning- drying of wood
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Methods of Seasoning Wood
1. Natural or air seasoning-one of the best
methods of seasoning lumber although the
period involved is relatively longer than the
artificial seasoning method. Air drying
Sun drying
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Methods of Seasoning Wood
2. Artificial seasoning-quick drying of wood
Kiln drying
Forced air or pressure drying
Vapor drying
Radio frequency dielectric drying
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AIR DRYING
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KILN DRYINGSEASONING
RADIO
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RADIO
FREQUENCY
DIELECTRIC
DRYING
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VAPORDRYING
M h d f T i L b
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Methods of Treating Lumber
Tantalizing
Permanizing
Wolmanizing
Bolidine salt
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