Wet Behind Interior Wall Behind Insulation

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Posted by: from Lloydminster
2/4/2013 at 2:43:07 PM

We decided to try reinsulating one room in the house which is always really cold. We are using the rolux. When we took the drywall off the wall there was a couple large areas on the wall that were wet behind the insulation and had frost. Why is that and should we be concerned?

We have let the spots dry out but wondering if we are good to start reinsulating? Should we be checking for something else or is it just because back in the day they did not use a heavy vapor barrier?

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Date/Time2/4/2013 at 3:13:29 PM


If your basement foundation wall is block as opposed to ICF poured concrete, you will have significantly higher hydro-static pressure - which draws moisture into the basement - similar in nature to capillary action.

Look for cracks in the wet area. How old is your home ? Over 40 years ?

Black tar paper should be between the block and the 2 x 4 wooden studs. Many builders cheat on this item.

If you call a reputable foundation repair expert, you should be able to get a free written inspection report.

Hope this helps,


Glenn Durkin

SPICA Construction Management


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Date/Time2/4/2013 at 3:50:15 PM

I would be very concerned. If its on a wood wall then you have a problem with the way the building paper is wrapping the house, or an issue with a flashing.

If the cause of this problem is not corrected it will lead to rott and mold problems. Same goes for the basement. Maybe a crack on the foundation. What ever way you look at it it's not good. And by covering it up, it will only come back to haunt you later.

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Date/Time2/4/2013 at 4:11:15 PM

You should be concerned but there can be a a couple of reasons.

1.) Is this a new home or is this the only room where you are really cold?

If this is a new home then perhaps there could be a block with the air circulation of the house, and there's condensation between the warm & cold air behind the wall.

2.) Is the room over a garage?

If it is, the cold air is making it's way throught the insulation to this area and creating some condensation with the warm/humid air.

3.) If the room is in an older home the basement or there's no vapout barrier.

Warm moist air in our homes from cooking, taking showers, having plants, breathing etc. That warm, moist vapor is attracted to the exterior walls. This vapor enters the wall through hairline wall cracks, outlets, switches and window trim. In new construction, the plastic vapor barrier under the drywall stops the wet air from getting to the insulation and condensating. In old houses with plaster walls, there is no vapor barrier under the plaster so the wet air hits the insulation and condensates.

Hope this is helpful for you.

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Date/Time2/4/2013 at 6:19:28 PM


The comments below all make sense and the main question would be the age of the structure.

I would, first, check for cracks (now that the wall is exposed) and also look for water patterns ... such as if it enters from one area and runs to another. The foundation should have been treated on the exterior to prevent seepage, but ??? If there is strong evidence of a crack, hole or other access point, I would contact a foundation repair specialist. It may require something that is beyond the normal houseowners comfort zone.

I would not cover it up until you can fine the source of the problem because it will just re-occure and the moisture could cause rot and mould inside the wall. (not a good thing). Don't be thinking of saving a few bucks on this one, it's your health at potential risk.



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Date/Time2/4/2013 at 7:42:13 PM

Good evening Sir / Madame:

First question I have is, is this room in the basement of a house or upper level?

Second question is, what is the age of the house in question?

And finally what type of dwelling is in question? Attached Semi-Detached Or Stand Alone?

This will determine the way in which the above questions are answered.

For a contractor to answer the above as accurately as possible in a way to be able to give you professional advice to benifit you more information is required.


Francis W Waines

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Sam from Busch Electric in Winnipeg
Date/Time2/4/2013 at 8:39:02 PM

Good day!

I'm not a basement expert. This sounds like your vapour barrier was leaking. If there is any way for inside air to leak around the poly your almost better off not to have a vapour barrier at all. I also recommend making sure it is sealed completely up in the floor joist. And if your only doing part of the basement you should seal that vapour barrier to the foundation at the ends of your work, that way if the part you have not completed is leaking badly it will not leak in behind your newly vapour barrier.

Your also supposed to try and not let your new insulation touch the concrete or brick foundation, because if there is moisture it will be held agains the foundation by the insulation and will cause mould. If you have a gap it will have a chance to dry up over time.

The best solution for this is spay foam, but it is allot more money, unless you can get a government rebate.

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Debora in Lloydminster
Date/Time2/4/2013 at 10:21:47 PM

Thanks for all the replies.

I should of been more specific. This is a bedroom on the main floor. My house is also 40 years old which is why I wondered if it was vapor barrior as it was not very heavy. No garage attached and is a single dwelling. Doesn't seem to have any cracks in the plywood. We do have a dryer vent on this side of the house but some of the wet steps were aways from the wall.

Not sure if this will change any of the answers everybody give me.

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Date/Time2/4/2013 at 10:21:59 PM

That will happen, but it's probably nothing to be concerned about as long as you are very careful with your vapor barrier. Make sure you use both ruck tape and accousti-seal on all of the joins.

This could indicate an issue with your house wrap (typar) but unless its excessive its unlikely.

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Date/Time2/6/2013 at 5:50:09 PM

Hi Debora,

Before considering re-insolating or vapor barrier please check around the dryer vent from the entrance into the house to be sure that the vent opening has been properly sealed due to the fact that if it is not the cold air coming into the house and the frosted wall will re-occur therefore you are going to have a re-occurance


Waines World General Contracting

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