How to Treat Mold in an Unheated Outdoor Structure
LESLIE: Now we’re heading over to Nebraska where Dan is on the line with a mold situation. What’s going on?
DAN: So I put up a pole building three years ago, and it’s a 48×36 and 10-foot sidewall. And I finished off about 700 square feet on the inside and sheetrocked it, put R30 in the ceiling, R19 on the walls. And it’s got a 4-inch slab concrete base to it. And this spring, I went out there and I had mold all over everything. And I don’t know what’s causing that. The first two years I never had a bit of problem.
TOM: Well, it’s been a very wet year. Now, you have no heat in this building, I presume?
DAN: I heat the bathroom, which is about 8×10 during the winter here in Nebraska, and the rest I don’t heat.
TOM: Well, look, mold needs three things to survive: it needs moisture, it needs air and it needs food. And all those things are available in that pole building. Your walls are made of drywall, I presume?
DAN: Yes, sir. Sheetrock. Mm-hmm.
TOM: Yeah, right. Drywall, yeah. So the paper facing, that is terrific mold food. And you have moisture there and you have plenty of air and you’re not heating it, so the humidity is always pretty high. And that’s why you’re growing mold. So, you need to at least ventilate the building. If you’re not going to heat it, just keep moving the air through it so it doesn’t – the humidity doesn’t become quite as high. But at this point, if you’ve got all that mold, that has to be treated.
DAN: Yeah. And I’ve done that. I’ve gotten that all out of there, right now, but I – and I put a dehumidifier in there just to …
TOM: OK. Well, that will help.
DAN: And it took me like 2½ days and I got it down to like 30 percent, so it came right down. Do I need to seal the floor? The concrete floor in there?
TOM: I don’t think that that’s necessarily the cause of the problem. I don’t think it’s a bad idea to seal the floor but I think that this is just a condition of the fact that you’ve got a damp building there with no central heating system, with plenty of drywall, plenty of moisture and plenty of air. So, just because of the conditions, the mold is going to grow.
Now, there were other ways that you could have constructed these walls. For example, there’s a product called DensArmor, which is a fiberglass-faced drywall that’s specifically designed not to grow mold, because it’s not organic. But with paper-face, in an un-heating building like that, I’m not surprised that it grew. Well, I am surprised it took two years but it might just be that it was just so moist this last year that it really took off.
DAN: How do I go ahead and vent that though?
TOM: Well, what I would do is I would probably have a fan based on a humidistat so when the humidity got really high, that it would kick on and draw air out of that building. Kind of like having an attic fan but on a humidistat instead of the thermostat, right? That plus the dehumidifier should help you keep the moisture to a minimum.
But keep an eye out for mold because, you know, once it gets started, then it really can take off quickly and it sounds like that’s happened in this case. So if you catch it sooner than later, you’re going to be much better off.
DAN: Yes. I want to try to eliminate it completely, so I’ll try that.
TOM: Alright. And when you do find it, make sure you treat the mold properly so that you kill the mold spores. Don’t just try to scrub it off, because it’ll come right back. You’ve got to treat it to kill the mold spores, then clean off the rest.