I’m fixing a hole where the mice get in to stop their poop from wanderin’

Our house
Was a very very very fine house.
But with a hole in the side yard, the cold it can no longer guard,
Now everything will be freezing ‘cause of you

TL;DR: One of the bottom panels of our fireplace/flue chase fell off and is letting rodents and cold air in. We’re not in the position to hire a contractor right now, so need to kludge together something on our own.

Pictures on imgur.

The ground beneath the chimney chase eroded over time, leaving it without support. The primary structural issues so far are that one panel of its foundation came loose and fell off and that there are two- to three-inch gaps beneath the remaining three sides. This is extremely problematic for a couple reasons.

In the short term, the house was built expecting the chase to be sealed, so there is little to no barrier between my furnace and fireplace flues. When temperatures drop, there is a lot of airflow coming from the outdoors directly into the unfinished basement. Plus, though it’s not their only entry point, it serves as a major mouse entrance—closing this off would help keep that down and allow us to call in the anti-mice specialists.

In the long term, without a suitable foundation, won’t the chase eventually just fall off the house? We will eventually call in a contracter to do a complete, structural repair.

In the meantime, I want to do a half-assed job to just seal it off. Looks are important, but not overridingly so (it’s on the one side of the house thta no one can see).

In years past, I tried using Gorilla tape to doubled-over heavy plastic sheeting (6 mil). I used sacks of dirt along the bottom to hold the sheets down and did my best to tape the tops to the vinyl siding. At the side with the missing foundation panel I used two layers of plastic with a section of fibreglass insulation sandwiched between. That had plenty of gaps (e.g. the tape didn’t seal well at the corners) and the tape didn’t stick very well to the sheeting, but all-in-all it made a huge change to the amount of airflow coming into the basement.

Short of hiring a contractor this year, and short of doing things that will make his job much worse (e.g. pouring a cement foundation that he’ll have to dig up), what else can I do?

Pour rock or sand into the gap at the bottoms to get a more solid seal?

Cover that with dirt before moving on?

Use a more specialized glue than Gorilla Tape (something that will strongly and easily bond to both siding and sheeting)?


Build a chase-chase out of pressure treated lumber. A three-sided wooden surround that fits against/around the existing chase. I bury the bottom in dirt (rock underneath?), then use caulk to fill in gaps in its construction and to seal it against the existing foundation (something like this crappy MS Paint drawing). I can see a few issues with that, mostly with how to seal it against the siding. Do they make a caulk that can fill ½ to ¾-inch gaps?

Ok, first stuff a bunch of steel wool into the hole. Mice will chew through it and die*. While your at it stuff a bunch of poison in the hole too, mice will eat it and die. Then fill in the hole with spray foam. I don’t know if that will kill mice also, but it will insulate. You can stick plastic onto the foam while it’s still wet. The rocks and sand at the bottom should work, I’ve done that for a temporary closure before.

*I can’t be sure this works, it seemed to work for me but I didn’t autopsy the little dead rodents to see if their stomachs were filled with bits of steel wool.

Poisoned mice will die inside your home, in teeny-tiny mouse-sized crevices you can’t reach, and then stink for a while. However, I’d think steel wool PLUS spray foam would make an effective anti-mouse and anti-cold barrier.

I have no specific advice, but I’d like to commend the OP on this thread title and opening song. :slight_smile: Do you have a contractor in mind already? If so, I guess you could ask him what would be the best temporary stop-gap (HA!) solution and what would make the long-term solution easier.

If you have dogs or cats in your home please do not do this. The mice will not die right away and will wander around in a dazed state for a day or two, making them easy prey for your house pets. Who will then eat them and ingest poison and possibly die or at the very least get sick.

No. The panels coming down from the chimney are not structural. The chimney holds up those panels, not the other way around. You need to seal the metal flue to prevent mice coming in, and then restore the panels for aesthetic reasons.

The chimney is not going to fall down. Nothing you do replacing the panels down to ground level or adding soil will affect the structural soundness of the chimney.

Side note: There will be no poisoning of the mice (or making them scrub dirty pots and pans). My primary goal is to fix up that hole. Once that’s done, we have a guy we know who will go down to the basement and read Vogon poetry for hours on end, freeing our house of pests (we and the cats will be in an air-tight chamber in Florida during the process).

Well that’s a bit of wonderful news. So then I can focus just on sealing off the chamber. I should have mentioned that the chimney(ies) passed inspection (both inside and by crawling into the chase from the outside).

Agreed, don’t use poison if pets can get at the poison or the dead bastards. In that case I recommend Have-A-Heart traps to capture them alive. Then feed them poison.

After have-a-heart capture, I’m supposed to launch them at least five miles away. I need to reread that goat/PVC cannon thread…

I was reading the Humane Society webpage on trapping, just a few days ago. According to the HS, relocating a house mouse sounds compassionate but the mouse is likely to die in unfamiliar territory. It’s a house mouse, after all. Field mice have a better chance of survival, tho the odds aren’t in their favor.

Might as well buy a bunch of snap traps and jelly beans so they’ll have a nice last meal.

It’s only been a house mouse for a day or so. Before it got in Rhythmdvl’s house, wasn’t it a field mouse?

the amount of poison was enough to kill a mouse. if a much larger animal eats the dead mouse they likely wouldn’t have serious effects., i’ve not seen cats (if fed well) be interested in a dead one, dogs are much larger.

Standard Portland cement, mixed with equal volume of gravel. Add some water until you get a dough. Push into every hole, everywhere. Once it is hardened,no rodent will pass.

This is good advice, and the following probably doesn’t apply to you, but be careful about sealing up all to holes, inside and out. That can trap rodents inside. Who then die. And smell. :eek:

My cats are well fed and declawed. I’ve found mice in the house with their guts eaten out many times. The guts must be the tasty parts. I’ve seen them play with chipmunks in the yard until they die and chipmunks eat poison too. I imagine a cat with claws who ran into an infestation of mice that were handled with poison instead of traps could easily catch enough mice to be at risk. The OP is talking about an infestation of mice.

i’ve seen cats just eat mice whole. crush the skull and swallow within 10 seconds.

mice eat the guts of other mice. i suspect for the liquids. i’ve seen plenty of snap trap dead mice with the guts chewed into in a no cat environment.

Board it up and jam whatever is laying around into the gap and then use foam insulation to seal it off until you can get to it and fix it properly. if you end up trapping mice indoors than take an empty cereal box, put standard trap in it and put it against a wall. mice like to follow edges. Empty box makes it handy to dispose of.

Mice that have lived in a building for multiple generations seldom do well when transferred outdoors. Outdoor mice tend to spend most of their lives outdoors, looking for indoor space during cold weather. They’re better adapted to finding their way around if live-trapped and relocated, but a lot of them don’t make it.

Fixing one hole and expecting a mouse-less home is bound to result in a bunch of mice laughing hysterically as they enter through a bunch of other, minute crevices.

My war on the rodent population now comprises about a dozen traps around the basement, baited with peanut butter (which mice love). So far this fall I’ve caught four.

Love those reusable easy-set plastic traps.

Gotcha, forget about the effects on the mouse population for now. The ‘Fixing a Hole’ Beatles reference in the title was half of things; the CSN ‘Our House’ opening is just as important—the gap results in a huge amount of cold air flowing directly into the basement, so I need to do something. Covering it with plastic sheeting did wonders, but there was still a noticeable airflow.

Here’s my plan—please poke holes in it (heh) if you see any problems with this or see things to watch out for.

I stopped by Lowes and picked up a slab of DuRock cement board, some exterior expanding foam insulation, and a bit of exterior hardware.

I pulled off the lowest piece of siding on the gap side. I’ll add a piece of scrap pressure treated 2x4 to the existing right-side frame to bring it up to the same plane as the newly exposed top board. This will allow me to attach the DuRock by its top and one side (it will also be supported by the ground).

For underneath the new panel, I got a bag of paver base and several bags of topsoil. I’ll start with a few shovels of rock (culled from the driveway), then cover that with the paver base. I’ll tamp it down as best I can (not sure with what just yet), then set the DuRock on it to get it into position to screw to the house. I’ll also use the paver base to fill the gaps between the ground and the other three sides of the chase bottom. Once all the gaps are filled, I’ll use topsoil to a height of six inches to a foot (and keep an eye on it to add more as it settles). I can’t really get to the back side of the panels, so don’t know if this will be an issue (if so, maybe I can convince our five-year-old that it’s some sort of game).

Lastly, I got a few cans of Great Stuff Gap & Crack expanding foam sealant (both regular and ‘large gap’). I’ll use this between the house’s foundation and the Durock and between where DuRock meets DuRock.

My other idea for the base (which seems like a lot more work so I’d rather not do it unless there’s a problem above) is to get a bag of cement, dig a smallish trench at the bottom of the new panel, and rest the DuRock in there while I attach it to the house. I’ll then stuff some cement into the gaps around the other three sides, then cover it all with topsoil. Would that be overkill or is it a much better direction than trying to use stone/dirt?

Or am I going about this wrongly and there are more sound ways of handling this?