I have a stucco-sided house that I am repairing/repainting. In the course of repairs, some of the caulk/weatherstripping between the trim and the house came off. The gap between the wall and the trim is fairly large -- at least 1/2 inch.

What's the best way to fill that gap? It seems too wide for a bead of caulk. But the product I pulled out of there doesn't seem like weatherstripping.

I have added a picture below. The first gives a reference of what we're looking at. The second is a closeup. The third is for a reference as to how big the gap is. I am a normal-sized human.

For reference


Size reference

  • Could you include a photo or two?
    – Tester101
    Oct 19, 2014 at 16:16
  • Sure, I'll take one right now.
    – Emily
    Oct 19, 2014 at 16:16

1 Answer 1


Correctly sized backer rod, a bond breaker, and properly applied sealant is the appropriate way to handle the joint between dissimilar materials with different coefficients of expansion [both thermal and moisture] such as wood trim and cement plaster.

  • Agreed, the loose material should be cleaned off as well, spot primed before the backer rod is installed. To be thorough, all the old caulk should be cleaned out, prime bare wood, add backer rod, caulk, reprime, then finish paint. Sorry, stepping all over your answer, which you answered his question, I simply seen a bigger picture here and added a few important details
    – Jack
    Oct 20, 2014 at 2:26
  • @Jack That's the plan. One question: what is a backer rod and where can I get one?
    – Emily
    Oct 20, 2014 at 14:09
  • @Jack I could post my three part CSI specification, but anyone who could make sense of it would already know the big ideas...and anyway, my experience is that such detail is useless for lay people [it's bad enough getting contractors to read it].
    – user23752
    Oct 20, 2014 at 16:23
  • @Arkamis backer rod is polyethylene foam. It is available in various diameters for various size joints. h-b.com/index.php?main_page=product_info&products_id=213
    – user23752
    Oct 20, 2014 at 16:26

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