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Sealing ceiling gaps to prevent mouse entry

734 Views 4 Replies 3 Participants Last post by  Once Upona Hack
This was posted in the pest forum, but got no replies, and I cannot move it, so here is that text again:

We have occasionally had mice in the attic area and (less often) basement, the entire 12 years we have lived in this 1990 house. The first winter I killed 32, but only a few a year since then. Despite the death toll, I still get more every year. I have looked everywhere and have sealed any possible entry sites. A possible big one 10 years ago was a poorly sealed soffit under a cantilevered bay window, with only vinyl siding spanning the joists. The air infiltration there before my work was horrible. Despite covering that with plywood and sealing it well, we still have mice.

I went above the aluminum ceiling over the mud room entrance and saw the remnants of a small acorn dinner party. I have seen other such shell scraps in the attic, but have never known if they are from the time period when the house was under construction, or are much newer. Once I have removed them, I do not seem to have them recur. I do not know where any gaps are large enough to let in acorns.

However, I now realize that the space between the bricks and this aluminum ceiling over the mud room entrance has gaps large enough mice can squeeze through them. I have access to both sides of this ceiling. What should I use to try to seal this? An image shows the gaps from below. I had not been concerned by them in the past, but they look more impressive from above, especially at the mortar at the end of each brick.


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Backer rod and color match Quad.

Get some stucco tape and tape off to the brick so that you don't get the caulk everywhere. Blue tape on the soffit.

Nice clean line.
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Backer rod and caulk is the answer I would propose as well. Tape both the brick and the siding, then add a liberal amount of caulk and press it in with you finger or a tool. Keep a rag and paint thinner to clean your tool or finger as you go. The tape keeps everything clean, but you should be tooling the majority of the caulk off the tape so removal is clean. Don't let the caulk set before you untape or you'll be sorry.

Also, where mice enter, there is usually evidence of smudges where the constantly rub against the entry point. This is a good visual cue to determine likely points of entry.
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I am aware of the skin/hair oil trails from frequent trips in an area, and I have never found any. Therefore, I have no idea where they have entered, or if I just have a colony that entered during construction, and have avoided extinction ever since then. Anyway, I will work at sealing any new gaps I find.

I have wondered if I can place the tape from below, but caulk from above, and avoid the need to "trowel" it at all. I have done the finger troweling with bathroom caulk so know about doing that.

I thank both of you.
You could also stuff something in the suspected gap (like fiberglass insulation) and watch it for a few days or a week and see if the area is disturbed. This would give an indication as to whether or not it is a point of entry and avoid the possible mess associated with caulking, etc.
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