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What can be done about recurring mildew on interior drywalls?
We’ve treated, scrubbed, and re-painted, but the mildew returns. Both are first-floor, outside-facing walls, in the San Francisco Bay Area.
An inspection of the crawl space revealed no moisture source. I don’t know if there is insulation behind the walls, although I would “assume” so, since there is elsewhere.
Any suggestions?
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You have too much moisture in the home. It is getting in somehow, through the heating system, through negative air pressure, or someway.
I might have an HVAC specialist do a test as to the air pressure and find out where this source of moisture is coming from.
*Ditto Scooter's comments ..... you may want to pick up a hygrometer and see what the relative humidity actually is. Have you always had the problem or did it recently start? There are many possible sources of moisture ....... bathrooms, dryers, leaky plumbing, leaks in the roof or walls.
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Thanks for the suggestions, guys. You give me the sense that at least we're on the right track. The problem has "always" existed --we've scrubbed and re-painted, but it eventually returns. I think we'll remove the sheetrock and do a thorough check inside the walls. The problem exists in both bedrooms, but nowhere else in the apartment.
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Steve, I'll back up Scooter's comments. Unless you plan on tearing off the drywall for some other reason, I wouldn't do this just to "do a thorough check inside the walls." In all probability you won't find anything.
I suggest you hire a guy to check for the neg. air pressure and/or poor circulation. My guess is your heating is woefully inefficient. If you have a central furnace, your ductwork is leaking causing a pressurization of the "non-living space", such as the attic or crawl space.
As for the mildew only showing in the bedrooms, its mainly the exterior walls where furniture is against the wall, right? And the walls are quite cold to the touch, right? The moisture source is the air.
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I agree with Rich. I think the problem is moisture on the inside condensing on the cool exterior wall. We breath and otherwise give off about a pint of moisture everynight in our sleep. We keep our bedrooms a little cooler than other rooms.
I bet if you beefed up the insulation in the walls, and got some airflow or heat in those mildew areas (farthest point from any heat source, right?) your problem would go away.
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It sounds to me like you have a very common problem. The fix is probably is two parts. First, because the mildew has been there for a long time you do indeed need to remove and replace the mildewed sheetrock. While it is off check insulation and structure.
If these are the only two walls getting mildew you may have an air circulation problem. Are these behind furniture, or somesuch? If you just had too much moisture in your home you would be getting signs elsewhere in the house too. Since you haven't mentioned any I'm assuming there are none. If in fact there are other signs then we're back to square one.
*At a recent continuing ed seminar, representatives from Armstrong told us that gypsum (in this case, gypsum-based flash-patching compounds) is by itself a food source for some molds.If this is true, how difficult would it be to include a moderate dose of mildewcide in the recipe for gypsum board? How 'bout it USG?Jeff C.
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What can be done about recurring mildew on interior drywalls?
We've treated, scrubbed, and re-painted, but the mildew returns. Both are first-floor, outside-facing walls, in the San Francisco Bay Area.
An inspection of the crawl space revealed no moisture source. I don't know if there is insulation behind the walls, although I would "assume" so, since there is elsewhere.
Any suggestions?