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Damp drywall due to improper vapor barrier install?

17K views 33 replies 10 participants last post by  26yrsinflooring  
#1 ·
Would improperly installed vapor barrier cause condensation at floor level and therefor cause the bottom 3 to 4 inches of drywall to because brittle/crumbly, and cause the floor to be cold due to drafts?

Backstory:

I bought a 1966 house that needs/needed some TLC. Ive installed new mdf baseboards in most of the house after the walls got a fresh coat of paint. One room to go and Im getting ready to install baseboards and notice the very corner of drywall is crumbling, further inspection reveals minor dampness in the corner (and now a 6x8 hold where I had to cut the drywall away). The bottom of the drywall seems soft but not really damp most of the way along the wall. I also notice that the vapor barrier isn't stapled to the bottom plate (at least in the corner but I suspect the whole length of the wall). If this is the case then I may have to remove the first bit (6-8 inches) of drywall along the wall and staple/(caulk?) the barrier to seal it. Theres no sign of mold, and from what I can tell the insulation behind the vapor barrier is in good condition, but I can only see a very small section right now).
 
#4 ·
Is this above grade, basement, or where?

Have you had carpet in this area? Sometimes the outside edge of the carpet (against an exterior wall) will be dirty. This is due to a leaky sill plate, and air constantly blowing in and out.
 
#7 ·
Please post a picture of the outside in that area.
Another guess that may have caused it is the outside sheathing and or siding was not installed below the sill plate so cold airs leaking in and when it hits the back side of the warmed plastic it's condensing.
 
#8 ·
If you are truly getting condensation forming in that area, and it is possible, it will be from a cold spot forming in the wall due to improper insulation. A poor insulation job such as a small gap, thin insulation, or too tightly compacted will cause a cold spot. Warm moist air from inside the house will condensate on the cold surface and over time will weaken and deteriorate the drywall.

The vapor barrier between the drywall and insulation, if properly installed, will prevent the moisture from saturating the insulation. However, it will not stop the formation of condensation if there is a gap between the insulation and vapor barrier. The insulation, if properly installed, should be tight against the vapor barrier to prevent any cold spots from forming.

Duct tape also should not be used in this application as over time it will dry out. There are specific products to use to seal vapor barriers in case of gaps or cuts.
 
#9 ·
There was a small bit of frost on the outside of the vapor barrier this morning. By the age of the house I could easily see that the insulation would be sub standard.

Heres the outside. Theres a few small cracks in the stucco but nothing major. If it warms up (its currently -24C/-11F) I could try to run a small bead of silicone between the stucco and concrete.
 

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#10 ·
I think my plan of attack is going to be:

-Buy some sheathing tape, some poly, and possibly a tube of acoutic sealant to fix the small holes and seal the corner.

-Patch the hole in the drywall

-Wait a few days and see if the drywall gets soft

-Run some foam weatherstripping/backer rod in the gap between the laminate and the drywall along the walls.
 
#11 ·
Does this drywall run all the way to the floor? It looks like it on the left. If it does this could just be water from mopping the floor. That is why we always cut the drywall 1/2" up from the floor. Drywall is very pours and will wick water like crazy.
 
#13 ·
What about previous owners? Once drywall gets wet and crumbly it rarely goes back to its original condition. The reason I bring this up is I really don't see any thing wrong with the insulation or barrier.
 
#14 ·
Is the floor concrete? For drywall to "get soft" will take more than a few days. IF wood frame floor, is the floor insulated? Vapor barrier on the dirt? Ventilated crawl-space? Is the wall VB taped to floor in picture? Was there a couch in front of wall there to restrict air circulation? The drywall nails are pretty rusted.... did you check various locations with a moisture meter ($25)?

Gary
PS. don't caulk/seal the stucco/parging joint or it won't drain if weeps were used...welcome to the forums!
 
#15 ·
I currently live in a home built in 1970.

I got into a wall while renovating the bathroom and was expecting to find R-11 insulation. To my surprise, I found R-7.5, which I didn't know had ever been offered.

When it is cold, I will get some frosty spots in corners and beside the exterior door.

I attribute this to the thin insulation, and it is quite possibly installed poorly, plus I like to keep the humidity high even when it is too cold outside.

You might want to see what you have there for insulation.

My solution is to one day re-insulate.
 
#17 ·
So after some more poking around the drywall (freshly painted) came off. The moisture was due to poor vapor barrier and insulation. What I found was not promising (it could have been a lot worse though).
The vapor barrier is/was 2mil secured with maybe a dozen staples along the top and loosely draped down. The electrical box was not sealed in any way, just a big gaping hole around it an the wall between the studs was covered in frost. I then tore out the drywall in the closet (also freshly painted) and discovered more of the same. I now have all the drywall, insulation, and vapor barrier on that wall removed and a handfull of lamps and fan going to dry it out.

I did a home depot run earlier today and bought some Roxul R14 insualtion batts, some more sheathing tape, some 6 mil poly, and some other random stuff. With any luck itll be dry enough tonight to re insulate, and tomorrow I can tear out the other wall and do the same.

Next week/weekend Ill be tearing down the master bedroom walls and doing the same. There will be just as bad if not worse.
 

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#18 ·
So I purchased a moisture meter and tested various areas of the wall. It ranged anywhere from 9% -17% (23 was the highest but the wood was still visibly moist). I also gave the walls a quick misting of anti mold spray (http://www.homedepot.ca/product/946-ml-concrobium-mold-control-trigger-spray-bottle/949056) for good measure. I also have a few fans and a dehumidifier running as well.

At what moisture level should I be safe to start re insulating the walls? Only smalls sections are reading 17% and higher.
 
#21 ·
First room is re-insulated and almost vapor barrier-ed. I ran out of sealant last night, I went a wee bit excessive on one wall. Started ripping the walls out of the master bedroom to check for moisture and luckily there was little to nothing. Theres were signs of dripping condensation on the wall. Aslo, this is how the outlets were "sealed".
 

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#24 ·
If you don't stop the moisture before the insulation you will get a greenhouse effect and the condensation will build on the inside of your vapor barrier and all you are doing will have little effect.
I am trying to wrap my head around the fact you stucco on your walls in Canada...
Stucco is neither moisture proof or vapor proof.
This was proven when they tried to use stucco in high humidity geographical areas.
It sounds to me like the problem is behind the stucco.
What is your average humidity ?
 
#25 ·
Im pretty sure the frost build up on the inside was just due to warm air condensing. The vapor barrier was extremely poorly done and the insulation averaged maybe 2 inches thick and was compressed in a lot of places. If my new stuff is R14 I would guess that the old stuff maybe rated R7. Some of the new vapor barrier and insulation has been up for about a day and there's no sign of moisture/frost on the inside or the outside.

Behind the stucco is most likely a layer or 2 of tar paper then plywood (which is where I had frost). The house is 47 years old and the stucco is doing pretty good, a few cracks here and there but nothing major.

The Relative Humidity averages 50% -75%
 
#26 ·
Back in 1992 I did a lot of work for a casino riverboat in Lake Charles Louisiana.
They had these large buildings built on barges and they had brought their west coast ideas and stuccoed everything.
The stucco could not take the moisture and relative humidity of the Deep South, about 89%.

It could not take the rain either,within a few short months they had severe moisture problems. They then started claiming they had intended it to be temporary anyway.

I am looking at this on the opposite side of the spectrum, you have such extreme cold and your humidity is high compared to where stucco is so prominent , the west, and in my home state Arizona.
I just don't see how that stucco has held up for so many years.
I had a builder uncle that used to laugh about installing stucco, he was from the northwest and he said stucco would never last in Washington state, the reason he was laughing is his exterior finish cost were cut in half by using stucco in Arizona as compared to WA requirements.

I don't think your problem is solved, I hope what you do works but I fear the cold in the form of frost will keep condensing into the warm spot close to your drywall.
We call plastic sheeting a moisture blocker but it is not a a vapor barrier.
 
#27 ·
Not sure I agree I live in Fla. not far from the Gulf and believe me we know about humidity and probably 95% of the homes here are stuccoed and we don't have have the problems you mentioned. When I lived in Ohio we had stuccoed houses although not near as many as down here.