7/21/2019 Sam Rogers' Common Wood & Lumber Defects

1/3

Common Wood & Lumber Defects

Back to Woodworking Home

Lumber defects are nothing more than imperfections in the media we use to build things. And,no matter what wood you use, some or all of them are going to be a little less than perfect.

Defects can be either "man made" or naturally occcuring. The point of this page is to identifythe types of defects that are out there, and maybe point a few fingers.

Man made defects can happen anywhere along the milling chain of events, from tree to tablesaw from felling to fillister plane. But, with only a couple of exceptions, more times than not,man made defects can be attributed to wood movement. No matter what species of wood youuse, you're absolutely going to experience movement or the change in wood dimension in oneor more planes due to the change in moisture content. And, most of these resolve to one of twotypes of problem... Either the wood was not dried with proper care or the wood distorts orwarps due to internal stresses because of inconsistent rates of moisture loss.

Naturally occurring defects are more "organic" so to speak. Natural defects are alwaysenvironmental, be they soil composition, changes in weather conditions, foreign invaders of onetype or another, or growth patterns. They will almost certainly show up as changes in color, butcan also represent as a physical defect as in wormholes.

Some defects, especially the natural defects, can be part of the design aesthetic and createstunningly beautiful pieces. Others can be worked around or incorporated to impart a certain"feel" for a piece. All of the man made problems though, will have to be corrected through themilling process. And, depending on the severity of the problem, some boards may not besalvageable and have to be discarded. Further, some lumber, because of the way it's initiallycut, may be prone to continued warp and distortion, even after milling.

Man Made Defects

Bow A curve along the face of a board thatusually runs from end to end.

Check A crack in the wood structure of a piece,usually running lengthwise. Checks areusually restricted to the end of a board anddo not penetrate as far as the opposite sideof a piece of sawn timber.

Crook Warping along the edge from one end to

the other. This is most common in woodthat was cut from the centre of the tree nearthe pith.

http://www.scrgeek.com/index.htmlhttp://www.scrgeek.com/index.htmlhttp://www.scrgeek.com/woodwork.html

7/21/2019 Sam Rogers' Common Wood & Lumber Defects

2/3

Cup Warping along the face of a board acrossthe width of the board. This defect is mostcommon of plain-sawn lumber.

Shake Separation of grain between the growth

rings, often extending along the board'sface and sometimes below its surface.

Split A longitudinal separation of the fibreswhich extends to the opposite face of a

piece of sawn timber.

Twist Warping in lumber where the ends twist inopposite directions.

Wane The presence of bark or absence of woodon corners or along the length of a piece oflumber. Wane in the form of bark is morecommonly associated with rough milledlumber. In the case of construction lumber(i.e., pine 2'x4's), it can be bark or missingwood.

MachineBurn

Discoloration of the wood due tooverheating caused by friction, and eitherscorching the wood or the resins within it.Machine burn is caused by stopping or notfeeding the wood across the blades at the

7/21/2019 Sam Rogers' Common Wood & Lumber Defects

3/3

correct rate of speed. Although specieslike cherry, pine, or walnut are moresusceptible than others, machine burn canalmost always be prevented by using sharp

blades and correct feed rates.

Back to Woodworking Home

Natural Defects

Blue Stain A discoloration that penetrates the wood fibre. It canbe any colour other than the natural colour of the piecein which it is found. It is classed as light, medium orheavy and is generally blue or brown.

Pitch An accumulation of resinous material on the surface or in pockets below the surface of wood. Also called gumor sap.

Loose Knot A knot that cannot be relied upon to remain in place inthe piece. Caused by a dead branch that was not fullyintegrated into the tree before it was cut down.

Tight Knot A knot fixed by growth or position in the woodstructure so that it firmly retains its place in thesurrounding wood.

Spalt Typically found in dead trees, spalting is any form of wood discoloration caused by fungi. There are threetypes of spalting that are typically incorporated intowoodworking as design elements, pigmentation (orsapstain), white rot, and zone lines.

Wormhole Small holes in the wood caused by insects and beetles.

Back to Woodworking Home

Resources

http://www.lowes.com/lowes/lkn?action=howTo&p=Build/StrtWWood.html#6http://www.coateshomecentre.com.au/tips_tricks/tip_wood_defect.htm

Back to Woodworking Home

Last Updated: Nov. 02, 2008Visitor: [an error occurred while processing this directive]

http://www.scrgeek.com/index.htmlhttp://www.scrgeek.com/index.htmlhttp://www.scrgeek.com/woodwork.htmlhttp://www.scrgeek.com/woodwork.htmlhttp://www.coateshomecentre.com.au/tips_tricks/tip_wood_defect.htmhttp://www.scrgeek.com/index.htmlhttp://www.scrgeek.com/woodwork.htmlhttp://www.lowes.com/lowes/lkn?action=howTo&p=Build/StrtWWood.html#6