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Sealing sill on added foundation

David Argilla | Posted in General Questions on

This may be a stupid question, but bear with me as I am doing this DIY. I am just completing a project adding a foundation and conditioned basement to my house. I poured the foundation wall up to the existing sill plate (actually 6×6 beam, house was originally post an pier construction). I did not use sill sealer or any gasket, as I thought that pouring the wall up to the beam would seal against air movement. But I didn’t consider wood shrinkage and expansion over time. Do you think that the periodic shrinkage of the beam will result in a gap that will allow airflow? I did include a capillary break between footing and foundation, as well as between footing and ground, so hopefully beam won’t be absorbing much moisture from the concrete after concrete cures.
Thanks,
Dave

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    David,
    Q. "Do you think that the periodic shrinkage of the beam will result in a gap that will allow airflow?"

    A. Yes. At this point you have two choices: jack up your house and slip in a capillary break / sill seal gasket, or caulk the crack between the beam and the concrete.

    Q. "Hopefully beam won't be absorbing much moisture from the concrete after concrete cures."

    A. Hopefully. It's a shame, though, that you failed to install a capillary break between the concrete and the beam -- it was a once-in-a-century opportunity.

  2. David Argilla | | #2

    Ok, thanks. Not going to jack the house up again, so best to caulk inside out of the weather? Or do both sides? Do you have recomendation for type of caulk?
    Half the perimeter of the house was sitting on a concrete foundation (looked like retrofit from perhaps the 30's or 40's), and the beam suffered no damage from that, so I'm perhaps unreasonably optimistic that the lack of capillary break will turn out ok.
    Thanks again
    Dave

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