If
you’ve ever had the pleasure of removing wood plank flooring,
you know that it can be pretty dusty underneath. The subfloor
was usually dirty before the flooring was even installed. Add to
that years or decades of extremely fine dust filtering its way
through the flooring and you have what’s known as a "bio-layer".
This is a layer of all things organic. Skin cells, pet
dander, dust mites (and their feces), mold spores, pollen, hair,
bacteria, aphids, cellulose, insect feces, lint, carbon
particles and yeast. In fact, it’s estimated that up to 70% of
household dust is made of discarded skin cells (all yours, I’m
sure)!
Wood can hold close to 40% of it’s weight in moisture (i.e. 40%
moisture content). Wood is dense and absorbs moisture very
slowly. Good news, right? Unfortunately, it releases it
even more slowly. Add to that a layer of finish on the top
and subflooring with felt paper beneath and wood floors can
remain wet for a long, long time.
Can
you see where this is going? You have an organic food source.
Moisture content above 16% for weeks or months. Warm
temperature. Minimal air flow. That’s right! You’ve got
ideal growing conditions for mold beneath your wood flooring. Does this mean that every
wood floor that gets wet will have mold growth? Absolutely not.
But these conditions are about as good as it gets for microbial
growth.