In the bottom of my sink's cabinet, the piping comes in through generously sized holes. This area is a mouse hot-spot. They come into the cabinet through here, and so as part of my overall rodent control strategy, I am thinking about filling these holes with expanding spray foam.

Am I going to regret doing so? There are obviously other alternatives, but spray foam is quick and easy.

Photo of piping under the cabinet

  • 2
    Whatever you do don’t use a metal product like steel wool on the copper I used to use steel wool because mice won’t chew through it and it holds the foam. A friend did this and had pin holes in a year or so.
    – Ed Beal
    Nov 21, 2021 at 6:56
  • @Ed - I hadn't heard that about steel wool & copper pipes. I was led to believe that steel wool was preferred because the mice can't chew their way through it.
    – SteveSh
    Dec 21, 2021 at 0:15
  • Another quick and easy alternative that isn’t nearly as messy is Duct Seal. Duct Seal is a dough-like product that often carries some form of fire rating (depending on manufacturer specification) and it remains flexible allowing you to reposition and remove it if needed. Dec 21, 2021 at 0:25
  • Spray foam is great where it can expand to the edges of a space. If under the floor were a small space, you could fill it with spray foam. Not great for this situation where you have huge spaces above and below and just want to fill a thin gap. Just use an old kitchen sponge. Cram it in there then use a knife to cut off the excess above. With spray you'll be filling the space below with foam. If you can remove the front plinth, put a flange below (see answer), a tiny bit of spray foam on it then cover with a flange above. Or make a perfect-fitting flange from wood matching the cabinet.
    – jay613
    Dec 21, 2021 at 16:01

2 Answers 2


I've used spray foam multiple times for this task, and it has worked well for me.

It certainly is quick and easy.

Just note that spray foam expands, so you may need to spray less than you think.

Some foams give off an odor as you spray it out, so I ventilate appropriately when using them. I don't know about toxicity of the fumes.

Many spray foams are sandable, and if you use one of these foams, you can improve the appearance. Plus, as you sand down, you can see if there are any air gaps.

  • Only side note is that you're also trying to block the holes in the subfloor, 3-4" below the bottom of the cabinet, so maybe use a long tube to get the extra reach. I don't know where you are, but around here, they sell a special formulation for 'pest control'. I don't know if that's hype or real, but it might be worth considering. Nov 20, 2021 at 22:14
  • 1
    @AloysiusDefenestrate I once saw that "special formulation" too. Like you, I wasn't sure if it was hype or real. Nov 20, 2021 at 22:27

I would try these:

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I know this doesn't answer your question but you can't put pictures in comments and it would be hard to describe with words.

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