Mold Behind Spray Foam on Basement Walls
Hello all,
A homeowner that hired us to do a kitchen remodel this winter has complaints about a smell of mold in their house. It’s not my field of expertise, but I offered to do a quick investigation. The house is on the coast near Portland, Maine. The roof is leak-free. No signs of water intrusion anywhere. Perimeter drainage looks good. There is no carpet. There is a full concrete basement. Ten years ago, closed cell foam was sprayed on basement walls and ribbons. That foam is exposed, meaning there has never been interior framing or wallboard. The basement did flood with 2″ of water 5 or 6 years ago during a torrential rainstorm when the ground was frozen and power was off so the sump pump was nonfunctioning. The homeowner fears that groundwater has infiltrated through the concrete walls and has encouraged mold growth behind the foam.
What do you think? Is this a viable theory? If it is mold, if I removed an area of the foam, would it be visible?
Thank you for any advice.
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Replies
ronletourneau,
Yes, if there is mold it should be visible. However I wonder whether that's the source of the smell? Closed cell foam is a pretty effective air-barrier, so that even if there is mold between it and the concrete I'm not sure how it could be affecting the house.
I'd be interested to know what the humidity level is in the basement? My first guess is it's high enough to encourage mold and mildew on interior surfaces.
Thanks Malcolm.
In the summer months, corresponding to the RH outside, there are times when the humidity in the house is very high. But there is no sign of mold anywhere--back of closets, bathroom ceilings, stored books, window sills, etc. The homeowner does run two localized dehumidifiers, one in the basement and one in the living room in an effort to address the smell.
To complete the picture, the foam is tightly adhered to the basement concrete floor and to the basement ceiling. The homeowner isn't happy with the idea of cutting holes in the foam to visually check for mold but that has been my suggestion.
Thanks again!
As long as the spray foam is fully adhered to the concrete wall, there will be nowhere for mold to grow "behind" the foam. I doubt that's a problem. Even if there was mold in some little void somewhere, the spray foam should seal that off from the living space, so you wouldn't have any smell.
I think Malcolm is probably right -- if you have high humidity levels, you could have problems in a wall or just about anywhere else with a surface. Do you have any batts you could easily access to check? I'd also check anything sitting on the basement floor.
Bill
Ron, I agree with the others that mold behind the foam is not likely the culprit; the flood wouldn't matter, as the concrete walls will be damp anyway from ground moisture. Does the foam extend up to the subfloor, covering the rim joists? Does the basement floor appear damp? Is the sump pit sealed? Is there a masonry chimney?
I have performed many mold investigations over the years. One of the less expectetd sources, and easiest to fix, is an open sewer vent. In many cases, sewer gases don't smell like "sewage," but they can often smell like mold. In several cases, the source was simply a dried-out trap in an occasionally used shower or sink. This is especially the case when the smells only occur occasionally - once the fixture is used, the trap is filled for another few weeks or months. In a few cases, the culprit was an open DWV line left inside a building cavity during construction or renovation. In this case, it requires the right combination of pressures for the sewer gas to find its way into the breathing space. Floor drains connected to the sewer system can also be a source, as many/most either have no traps or the traps are dried out. Finding any of these sources can fix an annoying problem and the generally low cost makes you the hero. Finding the ones inside wall cavities is difficult. in a few cases, I've resorted to using a blower door to depressurize the house and setting off a smoke bomb in the main sewer line leading from the house via the closest cleanout.
These are great leads.
The foam does extend to subfloor over the rim joist cavities.
The sump pump is under a seemingly well-installed and taped Teno-barrier that was put in to seal some exposed ledge in the basement. There is no evident mold on the underside of this barrier.
I'll check for any drains in basement.
I'm curious about Michael's question about a masonry chimney. This is a mid-century ranch and there is a large block chimney in the entry hall, where the smell is most troublesome. It contains three flues: wood stove in basement; gas boiler in basement and a gas fireplace insert in living room. There is a custom cap that appears to be well-installed. Might there be mold inside the chimney? How could that be checked?
Ron, I don't have a specific idea regarding the chimney but they are often uncapped and water eventually finds its way to the bottom. Groundwater can wick up as well; does the brick and mortar look the same at the basement floor as it does near the ceiling? Are there cleanouts you can access? Mold has a distinctive odor but it can be confused with other things, so I'm also curious if it's possibly wet creosote, furnace exhaust leaking into the house or something like that.
Had the same problem, stinky basement. Agree w/ Mr Engle, found an open sewer connection to presumably an old septic, left open to drain condensate from gas heater and hot water. Used foam and a plastic coffee can lid to enclose that connection, added a dehumidifier (from the local dump, simple repair) Smell went away in two weeks.