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Community and Q&A

Best practice to caulk clapboard and corner board area?

brp_nh | Posted in General Questions on

It seems that general practice is for the intersection of horizontal clapboards and corner boards to be caulked…a bead of caulk over this intersection after siding installation. But I’ve also seen advice about not doing this because the caulk can/will fail and trap water.

Our specific details are quarter sawn spruce clapboards and pine corner boards with a 3/8″ ventilated rain screen (Cor-A-Vent Sturdi Strips). Clapboards were primed on all sides from mill…and all remaining sides/cuts were stained by us during installation. We did use caulk during installation and kept joints tight, but things shift over time/seasons. Two story building with 18″+ overhangs. I think the ventilated rain screen would be a factor as it will help the siding and trim dry out better. There are more Sturdi Strips behind the corner board area, so not as much air space as the overall wall area.

Any wisdom from the GBA community…..definitely do a good job caulking this area because it will seal out water? Or skip the caulk because the building details (rain screen, overhangs, etc) should keep the siding/trim dry?


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  1. Expert Member

    When you say you did use caulk during the installation, do you mean you back-bedded the siding in caulking? If you did I would leave well enough alone.

  2. brp_nh | | #2

    We put caulk on the ends of the clapboards when installing them tight up agains the corner boards, but we were moving pretty fast, so it's not perfect.....and all the clap/corner board joints aren't tight after changing seasons. The work was done Fall 2014.

    I'm not too concerned with bulk water getting behind this area....the only real benefit I can see to caulking at this point is to try and "waterproof" this small intersection area. But since all wood surfaces are stained and there is good drying potential, this may not be necessary or could be negative if the caulk ends up trapping moisture.


  3. GBA Editor
    Martin Holladay | | #3

    You'll hear arguments from both sides on this one, but I am a firm believer in a caulk-free exterior.

    Your air barrier is elsewhere.

    Your ventilated rainscreen is designed to handle any moisture intrusion and to encourage fast drying.

    Under these circumstances, caulk does more harm than good.

  4. dankolbert | | #4

    As per, I agree w/ Martin. The caulk will fail, the chances of you or a future homeowner of re-caulking are approximately nil, so why bother? If you're relying on it, you're doing something wrong anyway.

  5. brp_nh | | #5

    Not using more caulk sounds good to me, thanks for the advice.

  6. charlie_sullivan | | #6

    I don't think the caulk would do any harm but if it's not needed, I'm sure you've got other things to do.

    By the way, nice look--I like the natural wood soffit with the painted rough-sawn siding, which should last well as well as looking good.

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