While some would argue that I am “nit picking,” the fact is that sometimes it is very important to understand the terms we use.
I am sure there are interesting studies as to just how things become "generic." Take Kleenex for example. Kleenex is a brand name that is commonly used to describe any kind of nose-wipe. While Kimberly-Clark Worldwide, Inc. may have an issue with the misuse of its brand name "Kleenex," the fact remains that when someone says they need a kleenex it really won’t matter too much who the tissue is made by as they all do pretty much the same job.
The term “Dry Rot” is similarly used to generically describe wood decay/rot in homes. The problem with using this term in a generic fashion is that there is a huge difference between actual Dry Rot and other types of wood decay/rot and requires quite different protocols for elimination.
All types of rot require that the wood have sufficient “free water” to support growth (for this discussion we will assume that oxygen, food and temperatures are suitable). Moisture levels to support Brown Cubical Rot, Soft Rot, and White Rot (the three most common types of rot) typically have to be above 30% for the organisms to be happy and prosper. With Dry Rot the wood moisture content will also have to have sufficient free water, but the wood gets to be at this level because the fungus is bringing the moisture to the wood as opposed to the wood being already wet.
This is a very important distinction because fixing a leaky roof or leaky toilet will be sufficient to stop the growth of most wood decay rot brought about by these conditions, but will not be sufficient to stop the growth of a fungus that is growing to the wood---bringing moisture to the wood from the ground.
Dry rot has the potential of attacking huge areas of a home’s structure without any real moisture issue already existing in the wood. Generally speaking brown rot or soft rot are more likely to be more localized. It can be more widespread if venting is inadequate or some other condition is present that elevates moisture levels in the woodwork above 30 percent, but generally speaking it will be more localized to the area of leaking---whether a plumbing leak or otherwise.
To date, there have been no documented cases of true “Dry Rot” in Washington State, but because of the Kleenex Effect---many people think it is common.
Charles Buell, Real Estate Inspections in Seattle