What might cause moisture inside walls?

laura_from_maSeptember 1, 2009

We're having the exterior of our house painted, and as the painters scraped the old paint, they found that the many of the clapboards and the wood behind them is entirely rotted. They opened some holes through the rotted wood and found the insulation soaking wet.

We do not have gutters, although after our experience today with the rotted walls, we're putting "install gutters" first on our to do list. However, the painter thinks that water INSIDE the walls (the sodden insulation in particular) would not be caused by a lack of gutters. He suspects there is another problem somewhere.

The house is perfectly dry from the inside. We have a one-year-old roof (with correct flashing, ice and water shield, etc.), and the walls were definitely wet with the old roof as well - so I don't think we can blame the roof.

Can anyone think of another possible reason for moisture inside the walls? Any idea what type of contractor we should call to investigate? Do you think it's just the lack of gutters, or do you agree with the painter than there is probably another issue?

Thanks for any advice.

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The lack of gutters could cause the problem. Also an opening in the siding could let a driving rain infiltrate. Are ther pipes running through the wall? Prior to the new roof being installed, perhaps water got in. without the gutters or with the older roof, water could have run back behind the facia board and inside the wall. Was the moisture barrier facing the correct direction?

If non of the above, I suspect you may have had too much insulation in the walls which would bring the dew point inside the insulation.

    Bookmark   September 1, 2009 at 9:42PM
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Is there moisture in all four walls?

Or mainly on the north side of the house?

Is the moisture barrier(if present) on the outside side of the insulation or behind the sheetrock?

And, how warm is the house kept in the winter and how cool in the summer?

    Bookmark   September 1, 2009 at 9:47PM
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We saw the problem (with the wet insulation) in two places -- one in a wall on the east side and one on the west side of the house (the roof slants towards these two sides). Both are places that we know get a lot of rain hits (one is where water falling off a porch roof hits the side of the house, the other is at a place where the house has sort of an "L" shape, so water splashes off one side of the L and hits the rotted side).

The north side of the house has very wet and slightly rotted clapboards (even the trim is rotted), but we haven't dug in enough yet to check out the insulation. The painter is planning to check the rest of the walls tomorrow, so I can hopefully give some more information then. From what I can tell, the south side of the house is comparatively fine. The paint peeled less on that side as well (although it did peel some).

There are pipes in one of the two problem walls, but not the other.

I have to admit that I don't know what the moisture barrier would look like. There's some sort of clear plastic up against the sheet rock (inside the insulation), there's also something on the outside that looks like black woven fabric with a silver paper-like surface (the silver side is towards the outside of the house).

I doubt we have too much insulation - we've done some work in other parts of the house and the insulation seemed correct for the age of the house (built in 1987), although it's a bit short of current standards.

We keep the house really cold in the winter - generally 60 degrees - and we don't have AC or central air, so the summer temperatures are about the same as outside.

    Bookmark   September 1, 2009 at 11:05PM
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No disrespect to your painter, but you should hire a home inspector, at the least, to determine your problem which sounds a lot like moisture exfiltration due to either no vapor barrier or one poorly installed.
The above can involve problems far worse than peeling paint.

    Bookmark   September 2, 2009 at 6:00AM
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I agree. This kind of problem is serious and requires professional investigation then analysis. You're just getting started.

    Bookmark   September 2, 2009 at 1:54PM
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Keep in mind trying to diagnose a problem over the internet is like opening a window on a hot day and air conditioning the Earth----.

Sounds like you have at least two problems. The most serious is that there is probably water getting into the insulation cavity. That problem needs to be found and corrected. Second is that if there is plastic next to the sheet rock and another barrier under the siding, the water getting in from the weather has no way to get out---cannot evaporate fast enough to dry out.

There is little use to paint anything until two thiongs happen---elimination of the water getting in problem and getting all the insulation dried out or changed. It sounds as if the siding needs replaced and even the sheathing replaced. If sheathing is replaced, the insulation can also be replaced---from the outside.

    Bookmark   September 2, 2009 at 3:06PM
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It sounds to me like we definitely need a professional to look into this. Is a home inspector a good place to start, or would we be better off with some other type of contractor (perhaps a carpenter)?

I appreciate all of the advice.

    Bookmark   September 2, 2009 at 3:52PM
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Home inspector---one with a LOT of experience.

Contractors often have little knowlege of specialty problems, however, an experienced roofing contractor might be the best second resource.

    Bookmark   September 2, 2009 at 8:01PM
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First you determine the scope and location of the problem. If it occurs where there is no overhang it isn't the drip edge.

If it occurs high as well as low it isn't splash back from the lack of gutters.

What kind of sheathing is it? OSB takes a long time to dry.

What kind of air/weather barrier? Perforated house wraps are not waterproof and others act as a vapor barrier preventing drying to the outside in a cold climate.

Are there trees and plants near the damaged area? This will eventually rot any wood structure.

Is it under windows? Windows are the most common place to leaks especially at the head and sills.

Is there a vapor retarder inside? In a warm humid climate it could prevent the wall from drying to the inside air conditioned space.

    Bookmark   September 3, 2009 at 7:38AM
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