More often than not, when you hear the words "dry rot", the term is being misused. It is often incorrectly used by the general public, builders, realtors, remodelers and (ugh) even home inspectors. Often what is called dry rot is merely rot (wood decay fungi). The common example of wrong usage would be wood that is under a bathtub. People bathe, the tub leaks and a beam or joist below rots and a rot probe might go clear through the lumber. Even if the wood is dry, this IS NOT dry rot. I teach wood destroying organisms for the state college system, Bellingham Technical College, and we offer classes at major cities around the state. One thing we make sure of is that students, at the end of class, know that true dry rot is rare. In fact, WSDA says it is not found in this state. Also, that term alone implies that wood can rot without moisture. In fact, wood requires 20% moisture to rot and usually a higher level than that for the rot to get started in the first place.
So what is true dry rot? It comes in two forms, and it is very distinctive. The two fungi are serpula lacrymans and meruliporia incrassata (more common in Europe). Both are vines that will grow from the soil to the wood. They attach to the wood and act as a conduit, moving moisture up into the wood...like wicking. So, bottom line: No vine then it is just plain old rot! You will have a pretty good clue as to how how much someone really knows about their profession if they are bantering around the term dry rot when in fact, they are talking about plain old rot. In wet northwest Washington an inspector almost never sees true dry rot, but lots of rot. Look at the photos below. The difference is startling.
This is NOT dry rot
This is dry rot, the vine wicks moisture from soil into the wood
Thanks for reading and the comments,
Steven L. Smith
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