Introduction to Construction

Softwood

Wood from trees that have foliage that remains green and functional throughout the year, and/or cone-bearing trees.

Hardwood

Wood from broad-leaved flowering trees.

Bark

Tough external covering of the wood.

Cambium

Reproductive tissue.

Sapwood or Alburnum

Younger, softer, living portion of wood.

Heartwood or Duramen

Older, harder, inactive core of a tree.

Annual Ring

Concentric layer of wood.

Springwood or Early wood

More porous portion, develops early, large, thin-walled cells.

Summerwood or Late wood

Hard, dark, less porous portion, develops late, compact, thick-walled cells.

Wood Grain

The direction, size, arrangement, and appearance of the fibers in a piece of dressed wood.

Edge or Vertical Grain

Wood grain resulting from quartersawing, having the annual rings forming an angle of 45° or more with the broad faces of a piece.

Flat Grain

Wood grain resulting from plain-sawing, having the annual rings forming an angle of less than 45° with the broad faces of a piece.

Mixed Grain

Any combination of edge-grained and flat-grained lumber.

Diagonal Grain

Wood grain having the annual rings at an angle to the length of the piece, resulting from sawing at an angle to the axis of a log.

Cross Grain

Wood grain having the cells and fibers running transversely or diagonally to the length of a piece as a result of a growth characteristic.

Close Grain

Wood grain characterized by narrow, inconspicuous annual rings with little difference in pore size between springwood and summerwood.

Coarse Grain

Wood grain having large pores.

Raised Grain

A dressed wood surface having the denser summer wood rising above the softer springwood.

Shrinkage

The dimensional contraction of a wood piece occurring when its moisture content falls below the fiber-saturation point.

Longitudinal Shrinkage

Wood shrinkage parallel to the grain, about 2% of radial shrinkage.

Tangential Shrinkage

Wood shrinkage in a direction tangent to the growth rings, about double that of radial shrinkage.

Radial Shrinkage

Wood shrinkage perpendicular to the grain, across the growth rings.

Warp

Any deviation from a plane or true surface of a board or panel, usually caused by uneven drying during the seasoning process or by a change in moisture content.

Cup

A curvature across the width or face of a wood piece, measured at the point of greatest deviation from a straight line drawn from edge to edge of the piece.

Bow

A curvature along the length of a wood piece, measured at the point of greatest deviation from a straight line drawn from end to end of the piece.

Crook

A curvature along the edge of a wood piece, measured at the point of greatest deviation from a straight line drawn from end to end of the piece.

Twist

A warp resulting from the turning of the edges of a wood piece in opposite directions.

Knot

The base of a woody branch enclosed by a subsequent growth of wood in the stem from which it rises. In the structural grading of a wood piece, knots are restricted by size and location.

Live or Intergrown Knot

A knot having annual rings intergrown with those of the surrounding wood. Live knots are allowable in structural timber within certain size limits.

Sound Knot

A knot that is solid across its face, at least as hard as the surrounding wood, and undecayed.

Tight or Close Knot

A knot held firmly in place by growth or position.

Dead or Loose or Encased Knot

A knot having annual rings not intergrown with those of the surrounding wood. Encasement may be partial or complete, but a dead knot is considered to be a defect since it can easily loosen or be knocked out.

Shake

A separation along the grain of a wood piece, usually between the annual rings, caused by stresses on a tree while standing or during felling.

Pitch Pocket

A well-defined opening between the annual rings of a softwood, containing or having once contained solid or liquid pitch.

Check

A lengthwise separation of wood across the annual rings, caused by uneven or rapid shrinkage during the seasoning process.

Split or Through Check

A check that extends completely through a board or wood veneer.

Wane

The presence of bark or absence of wood at a corner or along an edge of a piece.

Decay (Dry Rot or Pecky)

The decomposition of wood by fungi and other microorganisms, resulting in softening, loss of strength and weight, and often a change of texture and color.

Skip

An area on the surface of a board or panel missed by a planning machine.

Machine Burn

A surface charring caused by overheating of the cutting blades or abrasive belts during shaping or finishing of a material.

wood

a tough fibrous cellular substance that makes up the most of the stems and branches of trees beneath the bark.

Bark

cambium

sapwood or alburnum

heartwood or duramen

parts of the wood

softwood and hardwood

according to the classification of Philippine wood

according to strength grade

what are the classifications of wood

physical properties

refers to the aesthetic quality of a surface of the wood, usually determined by the visible wood grains

thermal properties

refers to the property of wood to withstand temperature fluctuations. also refers to the property of the wood to insulate a space from heat and cold.

pyrolytic properties

refers to the property of wood by which it can withstand fire up to certain degrees. usually this property of wood is aided by treatments using various chemical to produce an intumescent layer.

strength/mechanical properties

refers to the ability of a wood to withstand physical deformations due to forces acting upon.

shrinkage

warp

knot

shake

pitch pocket

check

split or through check

wane

decay

skip

machine burn

what are the common wood defects?

longitudinal

tangential

ra

what are the type of shrinkage?

cup

bow

crook

twist

types of warps

live or intergrown

sound

tight or close

dead or loose or encased

types of knots

high

moderately high

medium

moderately low

what are the strength according to strength grade (NSCP)