Trapped moisture

(Michael Larson, WI Lic. # 1672-106) #1


2005 build
Walk out basement
Poured foundation
House wrap behind vinyl siding over OSB
Unfinished basement walls
Trapped moisture behind vapor barrier on all but poured foundation portions.
Fiberglass batt insulation.
OSB not affected yet where checked
Minor organic growth. No odors.

I usually recommend removal of vapor barrier to let it breathe and dry out completely along with the use of AC and dehumidifier.

Any other views on this issue?

(Roy Lewis, CMI - North Florida Inspector) #2

Why did it get wet in the first place?

(Michael Larson, WI Lic. # 1672-106) #3

Apparent condensation. It does that up here. Moist air cool basement. Seen it many times.

Owner stated she seldom uses the AC and no de-humidifier present.

We no longer build way this because this happens. We use blue or pink board instead.

(Christopher Currins, CMI) #4

Yes, I agree. I’d definitely recommend to remove it and dry it out, and not reinstall it.

Is this area below ground? With your description I’m thinking not.

(Michael Larson, WI Lic. # 1672-106) #5

Its a walk out basement. The areas not exposed had no moisture behind the plastic.

I usually just tell them to remove the plastic or slit it and let it breathe.

The sad thing is that the vapor barrier was required when built. I’ve seen too many with rotted OSB as a result.

(Dennis DiVito, VA License # 3380 000170) #6

What would the walls be like if the interior sides were finished with drywall? How would you inspect that with knowing what you described as typical condensation issues in your region?

Just curious

(Michael Larson, WI Lic. # 1672-106) #7

You can’t.

It’s better if finished but once moisture gets in it’s like Hotel California. :wink:

(Roy Lewis, CMI - North Florida Inspector) #8

Besides all the rest of the comments… It does need to dry out…Yep!

(Erik Schmidt) #9

That’s interesting, vapor barrier should be on the warm side, so what side is that in Wisconsin in June and then December? I suppose I would recommend replacing batts with board, easy to do as basement is not finished and is proven to work in new builds.

(Michael Larson, WI Lic. # 1672-106) #10

That’s how it’s done on more recent builds.

(James E. Braun, CMI) #11

Get rid of the vapor barrier, so the moisture can more through the wall. In Missouri, we are starting not to put vapor barriers on the inside because of that reason.

(Michael Larson, WI Lic. # 1672-106) #12

That was my recommendation.

(Robert Young) #13

Just my hypotheses. Could be wrong. I would have to have equipment and see the site.

Water, Moisture defies gravity. Concrete saturated. Efflorescence is a condition that moisture is passing through the concrete. Water defies gravity.
The concrete wick moisture to the sill plate. Sud bays become a vessel to trap moisture evaporation from the sill plate.

The first sill plate, of the two, should be thermally protected. Flashed and Sealed. Built not to transfer temperature and moisture.
House wrap should be perm rated for that climate.

Just my 2 cents.

(Kenton Shepard, CMI) #14

I’m confused.

So, moist air from the interior moves outward toward the exterior through the insulation and OSB and then meets the vapor barrier which is cooler than the interior because it is colder outside than inside? That’s why warm, moist air is condensing on the membrane? Because it’s colder outside?

The housewrap is the vapor barrier you’re referring to… right? why do we see plastic on the interior of the wall with wet insulation behind it? You said the vapor barrier was between the siding and the OSB ext. wall sheathing, so it shouldn’t be visible. I’m totally lost here.

(Robert Young) #15

So very sorry, Michael.
After reading your post,

2005 build
**Walk out basement **
Poured foundation
House wrap behind vinyl siding over OSB
Unfinished basement walls
Trapped moisture behind vapor barrier on all but poured foundation portions.
Fiberglass batt insulation.
OSB not affected yet where checked
Minor organic growth. No odors.

the image appeared to me to be efflorescence on concrete. Damn. My eyes are going. So sorry.

Kenton brought me back to the thread with his reply and I concur.

If you could, or feel like it, could you describe the wall assembly once more please. Looking forward to your answer.

(Robert Young) #16

2005 build

Walk out basement
Poured foundation Requires anti damp at the very least.
House wrap behind vinyl siding over OSB. House wrap should be of a Vapor Diffusion Retarder type.

Unfinished basement walls
Trapped moisture behind vapor barrier on all but poured foundation portions. The interior Vapour Barrier. thin mill plastic, is leading to an increase in moisture related problems. Remove the plastic vapour barrier.

Fiberglass batt insulation. No issue when there is circulation.
OSB not affected yet where checked. Good.
Minor organic growth. No odors. Microbial growth can/may be a concern.

Remove the plastic vapour barrier.

(Michael Larson, WI Lic. # 1672-106) #17

Apparently you are confused.