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When placing an exterior wall on a slab floor for a single-story house, what is code for sealing where they are contacting?

70 by 70 | Posted in Building Code Questions on

I have been told all is needed is to line the bottom plate with Acusta seal, running either 2 beads along the bottom plate or in a criss-cross pattern.

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  1. GBA Editor
    Martin Holladay | | #1

    I have never heard of a product called Acusta seal.

    Most building codes require the use of a sill seal between the sill plate (which is usually pressure-treated) and a concrete slab. Sill seal is sold in 3.5-inch widths and 5.5-inch widths; the most common material is a thin, flexible, closed-cell foam (usually white).

    If you care about airtightness, it makes sense to supplement the sill seal with a bead of high-quality caulk, installed on the interior side of the crack after the wall has been framed and raised.

    It's also possible to use an EPDM gasket at this location; these are sold by Conservation Technology.

    Another high-quality sill seal product is Protecto Wrap Triple Guard Energy sill sealer.

  2. MParlee | | #2

    Another option is to use this
    We call it "black death" spend a little time with it and you will know why.
    The sill ends up being one of the leakiest spots in the entire structure if you rely on sill seal alone; not really sure why they call it "sill seal".

  3. jrinmichigan | | #3

    I just finished installing 160' of Protecto Wrap Triple Guard sill sealer. It seems to generally work as intended, but its very expensive (10x regular sill sealer was the best retail price I could find). It was also more difficult for the carpenters to deal with because it obscured the straight line they were used to having at the edge of the foundation.
    If I were to do it again, I would use a standard sill sealer, and then use a tape to bridge the joints between the concrete and mud sill and mud sill and rim joist. The Triple Guard sill sealer looks like it has Protecto Wrap's Window and Door Sealing tape joined to a thicker than standard foam sill seal material.

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