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jrb7911 01-26-2013 09:33 AM

Basement Bath No Vapor Barrier
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This bath was started without putting in a vapor barrier between blocks and stud walls. Brother says its fine, I say its not. Its a dry basement and block walls have 3 coats of UGL Drylock. Only 2 walls are exterior (under ground), the other 2 are just 2x4 stud walls in open basement. Its my understanding that a vapor barrier should have been put in between the stud walls and blocks, then insulated. No insulation behind shower either. Brother says nothing goes behind shower, says we insulate other stud walls and put vapor barrier between drywall and studs. I think he is wrong.
How should this have been done and what are our options short of convincing him to tear it all out and start over?

jklingel 01-26-2013 12:13 PM

i guess the first one never went, so.... first, where is this? i would absolutely install up to 3" of rigid foam in your exterior walls, leaving it loose enough to get the tip of a spray foam can in to seal it. no need for insulation in interior walls, unless noise is a concern. "wall is dry"; have you taped visqueen to the wall and let it sit a few days? water does not wick in buckets, so it can evaporate as fast as it wicks. you are probably ok w/ the drylok on. what appliances are going in? shower? tub? tile? etc. instead of relying on poly between studs and drywall, it may be better to use cementisous (however you spell that) boards, sealed. btw: pipes in exterior walls are to be within 1/3 of the way through the insulation; you may have a problem there, assuming the outside of the blocks does not have a ton of rigid foam and your soil gets cold.

stadry 01-26-2013 12:21 PM

gawd-save-us from brother-in-laws :laughing:

jklingel 01-26-2013 03:41 PM

that is spelled "bother-in-law":thumbup:

md2lgyk 01-26-2013 07:02 PM

This is very much a local code issue. How are we to know what's legal where you live?

Gary in WA 01-27-2013 02:09 PM

Good point, WHERE do you and your brother live? Or where is the house?


jrb7911 01-27-2013 05:01 PM


Originally Posted by md2lgyk (Post 1102734)
This is very much a local code issue. How are we to know what's legal where you live?

This is in northwest Alabama

Gary in WA 01-27-2013 07:47 PM

You are under the 2006 IECC;

No vapor retarder or barrier is required below-grade;

No insulation on basement walls is required per code;

However; with your Jan, Feb, and Dec. lows averaging 34*F (and your concrete wall above-grade +6" below), you need to keep the basement relative humidity below 27% with 70*F room temperature for no condensation there. With 1" XPS (R-5), the dew point is 33% RH in basement, for that small area during that cold weather temperature and below. Pretty mild.

Again, don't use a vapor barrier plastic or vapor retarder faced-insulation;


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