tough fibrous cellular substance that makes up most of the stems and branches of trees beneath the bark.
wood
softwood and hardwood
two types of wood
conifers (evergreens) which have needles instead of leaves , ex. pine
softwoods
broad-leaved trees or deciduous trees.
hardwoods
sapwood and heartwood
structure of wood
sapwood
softer,younger outer portion of a tree, usually lighter in color
heartwood
older,harder central portion of a tree, darker than sapwood. Central core of the log
decay,checks,knots,shakes,pitchpockets,wane,warping
defects of wood
caused by the attack of fungi
decay
cracks or lengthwise separation across the annual rings caused by irregular shrinkage during drying.
checks
cracks between and parallel to the annual rings.
shakes
irregular growth in the body of a tree which interrupt the smooth curve of the grain.
knots
well-defined openings between annual rings.
pitchpockets
lack of wood on the edge or corner of a piece
wane
caused by unequal shrinkage of the board.
warping
crook,bow,cup,twist
types of warping
distortion of the board. Long edge is convex or concave
crook
face is convex or concave longitudinal
bow
convex or concave across the board
cup
one corner is raised
twist
plainsawing,quartersawing,riftsawing
methods of sawing wood
lumber cut tangent to the annual rings. rings at an angle 0 to 45 degrees
plainsawing
wood cut radially to the annual rings or growth parallel to te rays. angle 45 degrees to 90 degrees.
quartersawing
30 to 60 degrees angle to the center of the timber.
riftsawing
woods suitable for use as a building material
timber
timber product manufactured by sawing, etc.
lumber
lumber that is surfaced with planing machine to attain a smooth surface and uniform size. s2s,s4s
dressed lumber
saw,edged and trimmed but not surfaced
rough lumber
lumber seasoned in a kiln
kiln dried
seasoned by exposure to the atmosphere
air dried/sun dried
strips, board lumber, planks timbers
4 classifications of lumber
less than 2” thk and at least 8” wide
strips
graded for appearance rather than strength. Same size as strips.Used for sidings and flooring.
board lumber
wide pieces of lumber 2” to 5” thick. Used for stairs, floor girders,girts and trusses.
planks
pieces of 5” or more on the smallest dimension.
timber
size of the lumber when is cut from the log
nominal size
board foot
lumber is measured in
number of pieces x thickness (in) x width (in) x length (ft) divided by 12. if the length is in inches divide by 144 for example: 18 pcs x 1” x 12” x20ft divided by 12 = 360 bd.ft but if the length is in inches 12 pcs x 3”x5”x36” divided by 144 = 45 bd.ft
board feet computation
when all free water is removed but all absorbed water remains
fiber saturation point
when the shrinkage of the wood occurs at moisture content percentages below the fiber saturation point. The drying of wood continues until the vapor pressure in the air just balances the pressure on wood surface.
equilibrium moisture content (e.m.c)
the process of removing moisture from green wood
seasoning
exposed to air
air drying
super heated steam is used to heat the wood and drive out the moisture.
kiln-drying
greater reduction in weight, control of moisture content to any desired value, reduction in drying time
advantages of kiln drying over air drying
used to forestall attack by decay,fungi or any harmful insects.
wood preservatives
oil-type wood preservative and water borne wood preservatives
2 types of wood preservatives
coal tar creosotes,creosotes derived from wood,oil and water gas,creosotes solutions,pentachlorophenol
oil type wood preservatives
chromated zinc chloride, chromated copper arsenate (cca) and ammoniacal copper arsenate (aca)
water borne wood preservatives
pressure treatment,hot and cold bath method,dipping or immersing the wood in a hot preservative for a short time, brushing
methods of applying wood preservatives
covering the wood with a compound or material,impregnating the wood in a chemical.
treatment of wood for fire resistance
wolmanized,tanalized,permanized,boliden
pressure treated lumber and plywood types