Mold in Basement Walls

John Rogers asks,

Hello, I live in Canada and we had mold in the basement. We had the exterior of the house graded away from the house, and had a spray foam insulation company come by and spray foamed our basement walls. I have since finished the basement to use as a rental property.

Last year, due to the gutters not being properly attached, we had some water fill up a window well during a heavy rain fall and come in through the basement window to the finished basement. This occurred in August — our tenants have stated that they smell mold in that room now (they didn’t smell anything before).

Upon inspection, there is no mold on the finished drywall and I personally don’t smell anything. I’m just wondering if it is possible that there could be mold behind the walls that they’re smelling — and if so, wouldn’t the mold make it’s way to the interior walls by now?

Any help would be appreciated. I know that the tenants never open the windows/blinds and kept the door closed for that specific room for awhile – so there was limited circulation.

Our Answer

John, the answer to your question is yes — mold could be growing behind the drywall but I’m not hearing anything that tells me a major destructive investigation is warranted. You could pull off some outlet covers, or registers or anywhere else you can get a peak behind but I would not recommend a major mold witch hunt. First, a one-off leak like you’ve described doesn’t usually cause a major mold problem. Sure, it can happen but if you have a leak, fix it and then move on, you often dont have the sustained moisture necessary for a major mold infestation. Also, I’m always suspicious when people say the "smell" mold. Its not like mold has a distinctive odor. They could just as likely be sensing the dampness since they dont ever ventilate the space. 
I will point out however, that drywall wasn’t the best choice for basement walls. There’s a product called <a href="http://www.buildgp.com/densarmorplus-high-performance-gypsum-panels" target="_blank">DensArmor which is a wall board</a> with a fiberglass face, instead of paper. Since the fiberglass is not organic, it can’t grow mold.
Before you go any further, I’d suggest that you install a <a href="http://www.santa-fe-products.com/product-solution/" target="_blank">good quality dehumidifier</a> in that area to really dry things out. Check out those from <a href="http://www.santa-fe-products.com" target="_blank">Santa Fe. Products</a>. I have one on my basement and it makes a bug difference, even though we also have all the exterior drainage set up correctly. I’m attaching the video I did with them recently. Hope this helps!
Tom Kraeutler