Mold On Lumber


I am looking for some information regarding black surface mold on lumber. Does it alter the integrity of the lumber stress values? I have a client who wants to use “all dry” lumber for his construction but I do not know if this is really necessary.


Generally, mold or stain does not have an effect on the lumber values. However, it may be a warning sign of high moisture levels, which definitely can cause problems. If the moisture content of the lumber is over 19%, two things will happen: lumber strength will decrease and decay can begin. If trusses were being designed and manufactured with green or wet lumber (over 19 percent moisture content), check with your plate/software vendor to see if the truss design should be modified. Do this even if you expect the moisture levels to drop to below 19% after the trusses are in service.

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