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Community and Q&A

Where to caulk wood siding?

arkitkt | Posted in General Questions on

I live in a 1920 wood sided house in Climate Zone 4.  We’re in the process of removing the vinyl siding and painting the old clapboards.  The old siding is in surprisingly good shape and so far needs little repair/prep prior to painting.  I’ve started to caulk the vertical joints around windows, doors, corner trim, etc. but I question caulking the horizontal joint under each clapboard.   I had not planned to do so but I’ve have more than one person suggest caulking it and say they’ve done it or have seen in done on numerous occasions with no problems.

In our situation, the siding is nailed directly to the studs (no sheathing) and behind the siding is either blown in cellulose or spray foam as both have been installed in the house at different times.  The logic as explained to me was the caulking would keep the wall insulation dry and basically provide a weather resistant barrier at the outside wall plane (we do have leaky walls).

Any thoughts on the pros and cons of caulking the clapboards?  Thank you.

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  1. seabornman | | #1

    I think the clapboards will move too much for caulk to remain in place, especially since it would be a tiny fillet of caulk laid on the overlap. If your walls haven't had moisture problems before, removing the vinyl siding shouldn't change conditions that much.

  2. Expert Member

    Caulking that many clapboard might break the bank!

    To mitigate Joel's concerns, you might gently pry the clapboard forward, and then run a small bead behind / underneath the clapboard, such that when released, it creates a nice smooshed layer that's not visible to the eye, yet would stop potential moisture migration through the gap.

    However, water doesn't really go through that gap anyways, so I don't think it would do much to stop water mitigation. You'll never create anything resembling an air seal with clapboard siding, so with all that, I'd vote as it's probably not worth the energy / time / $$.

    LP / Hardi siding isn't caulked in that spot either, just FYI.

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