Vapor Barrier - What's the real deal?


Old 04-29-05, 08:34 AM
Thread Starter
Join Date: Nov 2004
Location: iowa
Posts: 49
Vapor Barrier - What's the real deal?

Currently in the middle of finishing my basement. Not a walkout, totally underground. I know that most all the posts on this website say to put plastic next to the concrete and again on the outer wall. I was only planning on putting it on the outer wall. A local builder has told me that he does not put any vapor barrier in basements because it has a tendency to trap the moisture and give it no where to go. Even when they use kraft faced insulation they fold the tabs in rather than stable them to the studs. The only parts they plastic are the walkout sides or any wall exposed to the outside. I am in Iowa. Is this OK and if not why? My basement is dry. I can see the point if the basement had a lot of moisture problems, but then why would someone finish a wet basement?
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Old 04-29-05, 10:58 AM
Stevetra's Avatar
Join Date: Sep 2004
Location: Asheboro, NC
Posts: 348
Ok, I have done extensive research on this subject.....I have many old posts to prove this.

First off, dont assume that your basement is dry. There is moisture...or water vapor in your basement. You might not see it...but its there.

If you have sound walls...and no water problems of the liquit kind...then your in pretty good shape. You should seal your block or concrete walls with a product like Dryloc.

I will assume that you are building stud walls so you can run wires and insulate, make sure you use treated lumber on the floor...or anywhere the wood will touch the concrete.

Now...when you build your walls, keep them inside...or of the cement outside walls by about an inch. So what I am saying is leave 1" space between your stud wall and cement wall in the basement. (the studs dont have to be treated because they are not touching concrete)

When you insulate you will have a 1" air gap between the walls and the insulation, this will provide a area that will act like a moisture cushion, and allows the any moisture to disapate without causing mold.

Go ahead and provide a vapor barrier toward the inside of your newly constructed rooms ( between the studs and sheetrock)

Now this is the method that has the most data to support it. You will hear different opinions on this, but if you want it to last...this is the way to go.
Old 04-30-05, 04:47 AM
Thread Starter
Join Date: Nov 2004
Location: iowa
Posts: 49
Thanks for the clarification. I am leaving 1 inch between the wall and the concrete and using treated on the floor. Only did dry lock around a couple of windows. Will probably do it to the rest where I don't already have walls.


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