GLOSSARY OF TERMS
- Bark
- the convex side of the grain pattern when looking at the end view of the board.
- Bow
- deviation from a flat plane of the wide face, end-to-end. Caused
by a change in moisture content after sawing and by fibers not being
parallel to the surfaces. Has no effect on strength.
- Check
- a rift in the surface caused when the surface of a timber
dries more rapidly than the interior. End checks weaken the timber in
shear.
- Crook
- deviation from a flat plane of the narrow face, end-to-end.
Caused by a change in moisture after sawing and by fibers not parallel
to the surfaces. Makes wood unsuitable for framing.
- Cross Grain
- occurs when a board is cut from a crooked log. Wood is 10x stronger
in the direction of grain than across the grain. A cross-grain angle
greater than one part in ten weakens the wood in bending.
- Cup
- deviation from a flat plane of the narrow face, edge-to-edge.
Caused by a change in moisture content after surfacing. Tends to
loosen fasteners.
- Decay
- destruction of the wood structure by fungi or insects. Prohibits
structural use, but may enhance decorative value when the decay process
is halted.
- Decking
- boards or plywood nailed to the joists to make the top surface of the ramp.
- Joists
- on a deck, are the boards on top of the beams that support the full
load from the decking. Joists can extend beyond the supporting beams by
one-quater of the span.
- Knot
- high-density roots of the limbs. Knot are very strong but not
connected well to the surrounding wood.
- Oven-dry
- as dry as possible.
- Pitch Pockets
- accumulations of natural resins. Have little effect on strength,
but will bleed through paint.
- Shake
- a separation of growth rings. Should not be used to support bending
loads.
- Split
- passes clear through the wood and is often the result
of rough handling. Causes structural weakness and should not be
used in bending (joists) or compression (posts).
- Stringers
- boards that constitute the sides of ramps or stairs.
- Twist
- deviation from a flat plane of all faces, end-to-end.
Results from spiral wood grain and changes in moisture content.
Makes lumber unsuitable for framing.
- Wane
- presence of bark or lack of wood at an edge. Results from a
miscalculation on the part of the sawer. Has little effect on strength.