Dark Areas on Walls

On some interior walls in my house, I'm noticing dark patches that seem to be appearing between studs. The walls are sheetrock that have been painted a light color, and in several places, darkish, smokelike color is emerging through the paint. Most of them appear high up, near where the wall meets the ceiling. In the largest spot (about 3' high), I can clearly make out where two studs straddle the dark area, as if whatever is causing the darkening is trapped between the two studs. What could be causing this discoloration?
-Fleemo
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snipped-for-privacy@comcast.net wrote:

Moisture would be the number one likely culprit...
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Inadequate or nonexistent priming could be another.
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Abe wrote:

Why only in the stud cavities, then?
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back and forth through the wall, bigger dirt particles get trapped on the wall's surface. Only you will know if you can/should get more insulation and a proper vapor barrier into that wall. In the interim, I would scrub the wall and then prime the entire wall with one of the commercial products like KILZ which advertizes it will cover anything. Years ago (maybe still do) Glidden sold a vapor barrier paint for such problems. Other mfgrs may. You could get what you use tinted to match the current color if you are enamored of it. HTH
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Is your house in Toronto near Queen and Broadview?
http://www.thespec.com/News/BreakingNews/article/223746
Probably moisture.
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bmickey9

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snipped-for-privacy@comcast.net wrote:

Those areas are slightly different temperatures. That causes a little moisture to form on the cooler parts and that can trap dust or mold.
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Joseph Meehan

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Mold.
Check for roof leaks.
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Thanks for all the input here.

It makes sense it would be in this particular room. This room did have a leak in the ceiling which has been fixed. But do I have a bigger problem now? Will the mold go away now that the roof is fixed, or do I have to tear apart some walls? Is mold like this typically toxic? I have a new baby in the house and want to be sure to do whatever I need to do quickly.
By the way, the ceiling in this room is a vaulted ceiling, so there's not much space above it in the attic, but some.
-Fleemo
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fleemo,
If you think that it is mold then have an expert check so you'll know whether it is a harmful mold. Use some caution, there are many crooks in the "mold" business.
Dave M.
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David Martel wrote:

Good advice. Most molds are harmless, but some are not and there is no simple and accurate way for most of us to tell.
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So how would I determine whether it is indeed mold or not? Will it actually be fuzzy black mold on the wall surface? (It's up very high on a wall in a high-valuted room so I haven't been able to examine it closely yet.) If it is mold, must the walls be torn out, or is there a surface treatment I can use?
- Fleemo
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snipped-for-privacy@comcast.net wrote:

It is not all that easy to say. Based on my limited experience it has turned out to be mold about half the time. So far I have not had any of the deadly mold. I have had it professionally tested. Note, professional testers associated with mold recovery companies may not offer totally unbiased advice. A simple air test will almost always come up positive, the stuff is in the air. One test showed "positive" but the air outside showed about five times higher.
Usually a spray with bleach will kill it. If it is in the building materials I suggest that they should generally be replaced.
You may want to check with your local authorities, but be aware that doing that could, in some areas cause a lot more problems tan it solves.
Good luck
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Joseph Meehan

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snipped-for-privacy@comcast.net wrote in

What's above the ceiling? Attic? (possible roof leak) or 2nd floor? (plumbing or someone stole your shingles).
How's the siding look in those areas and above it?

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On Wed, 25 Jul 2007 12:06:27 -0700, snipped-for-privacy@comcast.net wrote:

1. You or someone else smokes too much. 2. Your furnace is emitting soot. 3. Satan is trapped inside the walls and wants your walls to look like HELL.
You choose which it is !!!!
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