We received this amazing picture showing white mold growing on wood in a crawlspace from one of our site visitors. We wish to thank them for giving us permission to use the picture for training people about mold. For confidentiality reasons we will not mention their names here. The picture was taken from the crawlspace of a new building which has a wood basement floor and wooden joists with a crawlspace under. The crawlspace was lined with poly vapor barrier and gravel poured over the poly to hold it in place. Unfortunately, prior to roofing, it rained and the water collected on top of the poly, creating a “pool” of water over the poly/gravel and under the wood floor.

The pool of water sat in this confined space with no air movement and no drainage until power was connected and a pump could be placed in the sump to pump it out. In approximately 8 – 10 weeks, the white mold began to grow. When it was first noticed, it varied in length from 1/4″ in length to 1″ and covered approx. 25% of the wood joists. Within 2 weeks, it had grown from 1 inch to 4 inches in length (approx. 4 times!).

What could the white mold be?

From the picture, it’s difficult to tell for sure. However, there are a number of common wood-rotting fungi that infest damp or water-damaged wood. We shall discuss this in detail in the next post.

Could this mold be a health hazard?

Probably not. However, if it’s not completely removed, it could destroy the wooden joists completely thus compromising the structural integrity of the basement floor.