GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

How to seal gaps between bottom of vinyl siding and flashing along chimney – roaches are getting in!!

kylefreestyle | Posted in General Questions on

Hi there. First time question asker. I recently bought a house in Durham NC (from Boston, MA). I’m having a nightly American cockroach (the giant ones) problem (inside the house) and according to the people who lived here the year before they had a constant cockroach issue.

I’m doing what I can with boric acid and other baiting/poison techniques without resorting to professional sprays etc. But I want to tackle how they are getting into the house in the first place. There are major gaps between the bottom of the vinyl siding and foundation and there are major chunks of brick missing along the entire height of the chimney (house used to be brick and they removed every other brick apparently on the chimney to install the vinyl siding, it seems.)

In terms of the gap between vinyl and brick foundation, previously someone had applied caulk to close that gap but it’s coming off. So I can go ahead and recaulk but a few questions first: 1) Does sealing that gap prevent the house from breathing and increase chances of mold? (Also dealing with some musty issues here). And 2) If it is okay to caulk could I used my AFM Safecoat caulk or is there something else that would last better? 3) Or does anyone have alternate ideas of how to seal that gap? Was thinking of backer rod / caulking or alternately some type of flashing?

In terms of the missing brinks along the chimney, there is a flashing installed but it hardly would keep mice or roaches out since it’s only tacked down in a few spots. Should I just tack the the hell out of it? Or any other ideas?

Thanks for your help! I’m desperate to solve this problem because it’s deeply effecting my ability to feel at ease in this house. 

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. user-2310254 | | #1

    Hi Kyle,

    I tried to find an article I recently read that was relevant to this topic. My recollection is it stated that bugs don't really like setting up house in the air gap. Because of the stack effect, there is constant air movement that tends to dry out the critters.

    The gap is more of a highway for providing access to the home's interior. You are on the right track in attempting to seal any cracks, but you have to be careful about not sealing up the weep holes in your brickwork. (There are screening products for weep holes, but I don't know how well they work.)

    I don't see why you couldn't use the AFM caulk, but a polyurethane product might be more durable. You may want to check out the air sealing articles on Martin's "How to do Everything" page. Lots of great advice there.

  2. kylefreestyle | | #2

    Thanks so much Steve! I really appreciate your thoughts and help!

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |