When installing exterior window trim (just some 1" x 4" boards), how do you fasten them to the house without hitting the windows nailing fin and weather proofing material on top of them?

For example, a vinyl window is installed into the frame with nails or screws through a fin that has holes in it. This sits on the exterior side of the frame. Then you put tape over it. I imagine when installing the exterior trim boards, you don't want to puncture the fin or the tape, but then I don't see how you can install the trim because the fin is at least 1" and the tape more like 4", but the trim board is only 4" wide.

1 Answer 1


Personally, we regard flashing tape as self-healing, to an extent. At least, to the extent that we don't worry about a few finish nails going through it.

See, that tape and those fins are really just to deter condensation, not full-blown rain leaks. A couple pin-holes are acceptable.

  • 2
    @tau: I agree with NPM: the itty bitty breach of a finishing nail—even if there were no sealing tape—is not going to let any water through unless there is something very wrong with the fin, trim, or nail. Nail it once cleanly. If you do have to pull it out and reinstall, caulk the first holes and nail it again in a (slightly) different place.
    – wallyk
    Aug 12, 2017 at 23:14

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