Q: When grading hardwood lumber, can incipient decay be included or not?

A: First, incipient decay (usually seen as a bleached white area surrounded by black zone lines that looks like someone doodled with a marker on the lumber) is caused by a decay fungus, but when using the word incipient, meaning beginning, we assume that the decay has not gone far enough to soften or impair the hardness of the wood.

Second, the  NHLA Rule Book  states (Rule 26) "stain, including spots in which the disintegration has not proceeded far enough to soften or otherwise change the hardness of the wood perceptibly, will be admitted in grades of species where the rules specifically state stain is admitted or in the grades of species specifying Sound Cuttings."

Third, what all this means is that on the clear face cuttings, there cannot be incipient decay. However, on the reverse of a clear face cutting, there can be incipient decay, as the reverse side of a clear cutting only needs to be sound. Note that some species (such as sap gum and aspen) and some grades (such as No. 2B Common) admit stain in clear cuttings or require only sound cuttings. In this case, incipient decay is permitted on both sides of the cutting.

Fourth, rot is when the decay has gone far enough to soften the wood. Rot is never permitted on the face or reverse side or on the interior of a cutting, either a clear or a sound cutting.
Fifth, the area of the lumber that is outside of the cuttings used to establish the grade can have incipient decay.

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