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Re: basement vapor barrier

From: info@builderswebsource.com
Category: Foundations and Basements
Remote Name: 63.198.181.43
Date: 18 Apr 2002
Time: 09:44 PM

Comments

Proper installation of vapor barriers is a confusing topic. Furthermore, a vapor barrier is only one component of keeping a basement dry. As a result, a dry basement is only possible when multiple design aspects are used in conjunction with each other, including proper foundation and downspout drainage, grading, installation of exterior moisture barriers, coupled with internal vapor barriers and proper installation.

A vapor barrier in a basement should always be installed on the "warm side" of the wall. That means between the face of the studs and the drywall. Why? To avoid condensation on the vapor barrier itself, you want to avoid a large temperature differential from one side to the other. If you were to place the vapor barrier over the concrete wall, or on the outside of the studs (before the insulation), you would likely see condensation on the vapor barrier. A damp-proofing bituminous (tar-like) coating on the exterior of the basement wall coupled with proper drainage will help to keep soil moisture out in the first place. The vapor barrier will help to prevent internal humid air from penetrating through the wall cavity, helping to prevent condensation on the concrete wall. The key is to ensure a clean installation.

Be sure to caulk all cracks and penetrations in the foundation to prevent accidental moisture entry points. Then, when installing the vapor barrier, use care to avoid punctures. Tape all seams from top to bottom. Some vapor-retarding paints are also available. As to keeping a space between the wood frame and the concrete wall -- this is a good idea. The wood should not touch the wall if possible. By using 2x4 studs, but spacing the drywall side of the studs about 6" from the concrete wall, you'll have space for R-19 or greater insulation which will help to keep your basement comfortable year-round. If you notice moisture problems before you complete this work, you must resolve the source of the moisture before continuing. Otherwise, you may lock in moisture inside the wall cavity, which could promote fungus, mold and wood rot.

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