Two recent tragedies in Berkeley and Folsom, California have caught my interest: first a balcony collapse, then a stair collapse. They each resulted in the loss of several lives and I can’t imagine what the families are going through. As usual the media are in frenzy with daily reminders of both tragedies. Almost every single article I read repeats a phrase in particular that grabs my attention: “dry rot.” From all the photographs, it is clear to me that the wood framing in both structures exhibited wood decay, or wood rot. Strength loss in this phase of decay is significant. But, the term "dry rot" is misleading and is often misused: the fact is, the rot did not occur because the wood framing in the building was dry, it happened because the wood framing was wet.
In very short terms rot, or decay, is the decomposition of organic matter by fungi. Simply put, fungi are basically mushrooms, molds and yeast. Fungi, like all living things, have four basic needs: water, oxygen, favorable temperatures, and a food source. In both tragedies, water, or moisture intrusion penetrating into the building envelopes--where the wood framing is supposed to be protected--was the likely culprit leading to wet conditions capable of supporting wood rot.
Truthfully, the only correct part of the term "dry rot" is the appearance of the rotten wood. In the advanced stage of this type of wood decay, the material becomes cubicle, or dry in appearance, similar to burned wood. It is because of this appearance that leads people to call it “dry rot.” Don’t be fooled by this label, wood rot results from wet conditions, not dry.