Keeping Critters Out: Sweeps and Steel Wool
Last two lessons we got the sweep on and the threshold sealed up right. This one's a little different. We're not just stopping air anymore, we're stopping things with legs.
Mice mostly. Sometimes bugs. Out here with the dry air and the fields not too far off, they're looking for a way in same as the cold is. And they don't need much. A mouse can get through a gap about the size of a pencil. I know that sounds made up but it's true, look it up if you don't believe me.
So this lesson is about the gaps a door sweep alone doesn't handle, and the cheap trick that fixes a surprising number of them.
Where they actually get in
Not usually through the door itself. Through the stuff around the door that we forget is even a hole.
- Gaps where a utility line or pipe comes through the wall near a door frame
- The corners where a door sweep doesn't quite meet the frame
- Cracks in old trim or siding right at the threshold
- Gaps under exterior utility doors, the kind that lead to a crawlspace or a water heater closet
That last one is basically how I learned this whole lesson.
One October I was doing my walk-through, same as I do every year, and found a gap under our utility door out back. Small thing. Maybe half an inch where the door met a wonky spot in the concrete. I hadn't noticed it because the door still closed fine and there wasn't a draft you could feel with your hand. But something had noticed it. A mouse had gotten in.
I sealed the gap with a door sweep, same kind we've been talking about, and packed a wad of steel wool into the little side gaps where the sweep couldn't fully cover. No more mouse. Small fix, but I was pretty pleased with myself for about a week.
Why steel wool
Steel wool is the trick most people don't think of. Mice can chew through wood, drywall, plastic, foam. They can't chew through steel wool, or at least they give up trying pretty fast. It's sharp and it hurts their mouths.
So anywhere you've got a gap too weird a shape for a door sweep or a strip of V-strip, steel wool is your patch. Stuff it in tight, packed, not loose. You want it wedged in there so it doesn't just fall out.
A couple notes on it:
- Don't use it near anything that's going to get wet all the time and rust and stain things, like right at a threshold that sees rain. It's best for gaps up higher, around pipe penetrations, corners, places that stay dry-ish.
- If you want it to look a little more finished, you can caulk over the top of the steel wool once it's packed in. Caulk alone won't stop a mouse, they'll just chew through it, but caulk over steel wool holds the wool in place and looks better.
- Don't use it bare-handed if you can avoid it. It's basically tiny wires and they'll get in your fingers. Wear a glove.
The gaps around the sweep itself
Even a well-installed door sweep can leave a triangle gap in the corners, where the sweep meets the frame at an angle. That's a classic entry point people miss. After you've got your sweep on, get down and look at both bottom corners with a flashlight if you have to. If you can see daylight, that's a gap something can use.
Small squares of steel wool tucked into those corners, or a bead of caulk if it's a tight seam, and you're done.
A gap I actually should've done right the first time
This is a good spot to bring up something Jason and I ran into on his garage service door a while back. We were putting new weatherstripping around the whole frame and Jason had bought the cheap felt kind at the store, the kind on a roll that's basically fabric with an adhesive strip. I told him it was garbage before we even opened it. He wanted to try it anyway. Fair enough, it's his door.
We got it stapled up, closed the door, and within about a minute you could already see it compressing flat where the door pressed against it. That stuff quits in one season, tops. We tore it back off and drove over to get the V-strip and did it right the second time.
I bring that up here because the same logic applies to steel wool versus other quick fixes people try for these little critter gaps. Some people just stuff a rag in there, or duct tape over a hole. That'll maybe get you through a weekend. It's not a fix. Steel wool packed tight, or steel wool with caulk over it, actually holds up and actually does the job a mouse can't get around.
My opinion here is the same one I've had all course: weatherstripping and sealing is where you get the most for the least money and effort in this whole house. A ten-dollar sweep and a two-dollar pad of steel wool solved a mouse problem that could've turned into a much bigger, much grosser problem if I'd ignored it.
Before next time
Walk around the outside of your own place and look for gaps at ground level near any exterior door, especially utility or garage doors. Bring a note of what you find, even a rough guess at the size, and we'll figure out the right fix for it together.