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King 11-19-2008 08:46 PM

Moisture Barrier Basement Soffits
I am finishing my basement and have a room that will have soffits covering utilities around the entire perimeter of the room. Two sides of the room will be against a poured foundation wall which I plan to apply a plastic moisture barrier over the studs and insulation. Do I wrap up the wall and then out and up over the soffits as well? This is the only way I can think of doing it and keeping the integrity of the seal. I am in Atlanta area so pretty mild climate.

glennjanie 11-20-2008 09:58 AM

Welcome King:
Yes, that sounds like a good plan to me. With that moisture barrier you should have a nice dry basement.

CyFree 11-21-2008 10:20 AM

Did I understand that correctly?
You are to run the vapor barrier over the insulation and the studs?

In that case I have two questions:

Are you using wood or metal studs?

What kind of insulation are you planning to use?

Here's why:
The moisture seeping through the concrete wall due to capillary action (reason why you need a barrier in the first place) will eventually condensate behind the vapor barrier - or on any surface you place behind it and in that case, it will be condensing on the insulation and the studs.

Depends on the insulation you are using, it will soak up water and might support mold growth.
The same goes for the studs. If they are wood, they will soak up water, grow mold and rot.

Mold thrives in moisture and feeds on organic matter.

I recommend placing the vapor barrier behind studs and insulation linked to some kind of baseboard or internal perimeter drainage system. This way the moisture build up can be diverted to a drain or a sump pump.

I figure if you are going to do all this work yourself, you want to do it once and for good, therefore keep that in mind if you don't want a musty and smelly basement in the future.

Here's a good article on finishing basement walls with a comparative chart:

Picking the Best Basement Wall Products

inspectorD 11-21-2008 04:11 PM

I agree
Plastic against foundation, then studs and insulation, then no vapor barrier.
Basements are tricky, it depends on moisture levels, and where you live.
And buy a really good dehumidifier that drains itself:D

If you do it your way, you are encapsulating organic material as was said by Cy. Bad idea.
Let us know what you decide and if we can help further.:)

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