Q. I am working on an old oak timber-frame house which has been infested with powder-post beetles. The exterminators say the beetles are gone. How can I test the extent of the damage to the beams?

A.There is no practical nondestructive test for the strength of wood that is already in a structure.

The damage must be evaluated on a case-by-case basis. In general, if the damage is in an area where the primary load is in bending, there must be enough undamaged wood at the top and bottom of the beam to withstand tension and compression, and enough in the center to withstand the horizontal shear. If the damage is near the beam ends, there must be enough undamaged wood to provide bearing.

The only safe thing to do is to reinforce the infested members so that you are not depending upon their original strength.