As a result of a deep-energy retrofit/remodel, my exterior walls are now 1/2" sheetrock backed by 2" of polyiso foam against the studs. We are now trying to install trim (casing, crown, and baseboard plus some other decorative elements) to our walls. Normally I use an 18ga brad nail to attach interior trim, but, it doesn't seem that nailers exist in either 16ga or 18ga that can handle nails with enough penetration to reach the wood. Plus, even if the gun existed, I can't find nails in that length.

While I can use a wood backer on the crown that is screwed into the studs / joists, this wouldn't work for the rest of the trim without removing sheetrock. Removing sheetrock reduces one of the layers of air sealing, so that's a no-go.

Other than gluing the trim onto the sheetrock, which I hate for repairability reasons, is there another good strategy for attachment?

  • #9 x 4 in. Star Drive Trim Finishing Trim Head ScrewHome Depot. Or the available equivalent.
    – Mazura
    Apr 21, 2020 at 23:14
  • @Mazura Screws suffer from similar repairability issues as glue. They'll tear out before they pull out. Apr 24, 2020 at 0:17
  • It's either glue, screws, or hand-bangers, but I like none of those options. IDT you get repairability. So GL, +1.
    – Mazura
    Apr 24, 2020 at 1:37


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