Glencoe: Section 61 Flashcards
Lumber Defect:
Flaw that detracts from the quality of wood in either appearance of usefulness
How many characteristics are considered when wood is graded?
25
Warp:
any variation from a flat surface
It includes:
Bow, Crook, and Cup
Carpenters can cut flawed 2x4 into
blocking
The width and thickness of lumber given by two types of measurements:
Nominal and actual dimensions
Nominal:
size of the board in inches as originally cut in width and thickness, not its length.
After the board has been surfaced and seasoned at the mill, its X
actual dimensions become less than its nominal dimensions.
Building codes use X dimensions
actual dimensions
Dressed sizes apply:
after the wood has shrunk and been surfaced with a planning machine
2x4 actually measured in dressed size:
1 1/2 x 3 1/2
Why have sized of lumber been standardized?
Convenience in ordering and handling
Softwood lumber is readily available in actual lengths of
8’, 10’, 12’, 14’ and 16’
Common Nominal dimensions of softwood:
2”, 4”, 6”, 8”, 10”, 12” in width
1”, 2”, 4”, 6” in thickness
Are hardwoods standardized for length or width
no
Hardwood thicknesses:
1/4”, 1/2”, 1”, 1 1/4”, 1 1/2”, 2”, 2 1/2”, 3”, 4”
2x4 is actually
2x10 is actually
once you get into 2 x 8 you
1 1/2 x 3 1/2
1 1/2 x 9 1/4
drop to a quarter
The united states is the only lumber producing country that does not
use metric system.
Wood imported using metric have these dimensions
thickness and width in MM
length in meters
Wane:
– The presence of bark, or the lack of wood from any cause, on the edge or corner of a piece of lumber.
Bow:
A flatwise deviation (bend) along the grain from a straight true surface. Bow is measured at the point of greatest deviation.
Crook:
an edgewise deviation (bend) from a straight, true surface. rook is measured at the point of greatest deviation.
Cup:
flatwise deviation (deviation) across the grain from a straight true surface, cup is measured at the point of greatest deviation.
Check:
Small crack that runs across the growth rings. Occurs as result of seasoning
Shake
lengthwise grain separation through or between growth rings. May be further classified as ring shake or pitch shake
Split:
Lengthwise separation extending from one surface through the piece of lumber to the opposite side or an adjoining piece
Decay:
Disintegration of wood due to the action of wood destroying fungi (dot, rot, unsound wood)
Knot
Place where branch once grew. Classified according to size, quality, and occurrence. Measured by averages.
Knothole
left by the removal of an embedded knot
pitch
accumulation of resin in the wood cells
Stain
discoloration on or in lumber other than its natural color
Torn grain
torn spots created as the broad is machined to size
Decay and damage by insects to wood is most likely to occur when:
wood is wet
A house must be designed to encourage rain water to
drain away
Water vapor is given off when
cooking, washing or other household activities
Water vapor can do what to a house
pass through walls, ceilings, when it reaches a cold surface it forms water droplets.
Sources of water in homes:
rain, water activities in homes, leaking pipes.
What can allow water into homes:
gaps in exterior wood trim or between a chimney and siding
Wood will not rot if
it is kept dry
Fungi needs:
air, warmth, food (wood), moisture
Dry rot
An advanced type of decay where wood is Brown and crumbly. Wood may also be white and spongy
Decay wood is often indicated by
sunken areas on surface or a hollow sound when wood is tapped with hammer.
Fungi can grow on surface of wood if
air around is very damp
Fungi grow most rapidly between
70f and 85f
Moisture content of X or less is generally dry enough to stop fungi
20% or less
When untreated, sap wood of all common native woods
have low resistance to decay
Natural decay resistance of native woods lies in the
heartwood
Of the commonly used species in household construction, which wood has high resistance to decay
Bald cypress, redwood, and various cedars
Why is heartwood becoming harder and harder to obtain
increasing amounts of timber are cut from the smaller trees of second growth stands in which little heartwood has developed.
When decay resistant woods is needed
Preserve treated wood is used
Insects that damage wood:
termites, carpenter ants, and beetles
Termites:
termites are the most destructive of the insects that infest wood.
Best way to protect against termites:
during planning and construction: remove all woods debris such as stumps and lumber scraps from the soil before and after construction. Also NO WOOD MEMBERS SHOULD BE IN CONTACT WITH SOIL
Forms of termite protection:
chemical termiticide, physical barriers and treated wood
Two types of termites:
Subterranean and dry-wood
Subterranean termites:
account for 95 percent of termite damage. They eat the interior of wood and cause most damage before they are detected. They effect Hawaii and southern 2/3 of united states. They thrive in moist warm soil containing food. They build shelter tubes over foundation walls and pipes about 1/4 to 1/2 inch.
Two types of termite blocking methods:
Metal shields 12” min above ground, and covered soil.
Most destructive termite:
Formosan termite
Dry wood termites:
Fly directly to the wood instead of building tunnels from the ground. Less destructive
Carpenter ants:
Northeast, northwest, midwest.
Nest in ground as well as dead trees, firewood, and houses. Do not eat wood but plant juices, insects honey and food particles.
How do carpenter ants damage wood:
irregular tunnels they create for their nests.
What indicates a carpenter ants presence
small sawdust particles.
Control for carpenter ants:
chemicals
Two types of beetles that cause damage to wood:
powderpost and deathwatch
Powderpost:
Enter house via already infested wood, only attack hardwood
Deathwatch:
eats both soft and hard wood
Carpenter bees:
cut 1/2” diameter hole in bare or untreated wood. Build nests by boring tunnels.