Lumber Defects and Grading

Knot

a portion of a branch that was part of the tree at one time.

Blue Stain

Discoloration caused by mold or fungus. This happens when a log is cut and left in an area with high humidity.

Pitch Pocket

An opening in the wood containing resin, which may be solid or liquid

Bark Pocket

Bark material that was enclosed as the tree grew

Warp

Any deviation from a true plane surface that results in shrinkage (bow, crook, twist, wind, kink, wane)

Bow

A curve across the width of the board.

Crook

A curve along the edge of the board, sometimes referred to as the crown

Cup

A curve across the width of the board.

Twist (Wind)

A board that looks as though it is spiraling.

Kink

A deviation along the board caused by a knot or irregular grain pattern.

Wane

The presence of bark or absence of wood or corners or edges.

Split

A crack caused by a separation of wood fibers along the grain traveling the length of the wood. It is perpendicular to the growth ring.

Check

A crack like split, also caused by a separation of wood fibers along the grain but shorter and found at the end of the seasoned boards.

Shake

A crack caused by a separation between the annual growth rings.

Case hardening

The inside of the board is under tension and will react unpredictably when cut; this is caused by improper drying .

Honeycomed

A severe case of case hardening. The tension between the inside and surface of the board becomes so great that cracks develop in the core, which may or not be evident from the outside.

dimension lumber

Lumber with a nominal thickness of 2" up to but not including 5" and a nominal width of 2" or more.

Grade yield

The amount of NO.1, NO.2, and NO.3 lumber the mill obtains from its logs

American Softwood Lumber Standard(ALS)

Southeast U.S. lumber grading rules.

4 species of yellow pine:

1.) longleaf

2.) short leaf

3.) slash

4.) loblolly

Manufacturing defects

Defects that result from sawing and dressing lumber.

wane

A piece of lumber cut from the near edge of the log, near the bark

lumber drying

Most southern pine is dried to about 19% moisture content.

Drying defects of lumber

*warps

*splits

*checks

Skips

Created on a piece of lumber where the piece is not big enough for the planer to fully remove the rough portion of the lumber surface

Nominal sizes vs. dressed sizes

2x4 - 1 1/2x3 1/2

2x6 - 1 1/2x5 1/2

2x8 - 1 1/2x7 1/4

2x10 - 1 1/2x9 1/4

2x12 - 1 1/2x11 1/4

compressed wood

Abnormal wood that forms on the underside of leaning and crooked coniferous trees.

Slope of grain

Deviation of the line of fibers from a straight line parallel to the side of the piece. (Blue stain often represents slope of grain)

Decay

Disintegration of the wood substance due to action of the wood-destroying fungi

Holes

Extend partially or wholly through the piece. Classified as pin, medium, large, or very large.

Wormy pitch

Insect damage caused by grubs of pine Sawyer Beatles