Found a small area of dry rot at the end of a beam (actually 3 sistered 2x10's) where the beam is notched into the side of the foundation wall in a crawlspace. The dry rot appears localized to the last few inches of the beam next to the foundation wall, and does not appear to extend beyond the surface into the wood more than a 1/2-inch. No moisture present at time of inspection, and no obvious source of exterior water infiltration. There was no moisture barrier between wood beam and concrete, so I tend to assume the moisture was from condensation at the concrete contact point. Home is a 19 yr old log cabin. My question is this; is dry rot progressive, can the area of rot continue to expand in the absense of moisture?