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Community and Q&A

Concrete Sealer on Stem Walls?

hunter_w | Posted in General Questions on

Building a project that has a conditioned crawl space.
Should we seal the exterior of the concrete stem wall to help exclude moisture?
I do worry that we want the walls to be able to dry to the outside, since the XPS on the inside will be a barrier.
Advice on what to do, and product recommendations (is ‘green’ possible?) would be much appreciated.

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  1. GBA Editor
    Martin Holladay | | #1

    At a minimum, you need to install asphaltic dampproofing on the exterior of your crawl space walls. This is standard practice. Some builders suggest upgrading to a waterproofing system that may include a dimple mat. Whether this makes sense depends on soil conditions and the height of the local water table.

    There is no need for your crawl space walls to dry to the exterior or interior, assuming they are made of concrete. For more information on this issue, see Joe Lstiburek Discusses Basement Insulation and Vapor Retarders.

    For more information on crawl space specifications, see Building an Unvented Crawl Space.

  2. hunter_w | | #2

    Sorry if I wasn't clear - I am speaking about the above-grade portion of the stem walls.
    Below-grade dampproofing is taken care of.

  3. GBA Editor
    Martin Holladay | | #3

    There is no need to install any sealers or moisture barriers on the exterior above-grade portions of your foundation walls.

  4. hunter_w | | #4

    Martin, thank you very much!

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