Rodents getting in past cinderblock skirting

[Telkwa]

The mobile has been on-site for about 10 years now. We're getting some mice, and I think chipmunks too, underneath. My wife doesn't want to poison. Especially not chipmunks!

The mobile is perched over cinderblock skirting, with Hardiboard overlapping the top course of the cinderblocks. Since poisoning is not going to go over well, I'm trying to figure out a way to physically barricade. The cinder blocks are rough and irregular, so I'm thinking whatever I use is gonna have to be something that's sort of 'springy'.

About the only thing I can think of is stripping off the Hardiboard and then nailing or screwing the toughest hardware cloth I can find to the bottom edge of the mobile. Then rolling the hardware cloth back onto itself a few times and stuffing that into the gap, so that there's a springy roll of HW cloth filling the gap between the bottom of the mobile and the top of the blocks. One weakness I can see in that plan is the cinderblocks' holes. If the rodents can duck into the holes then pop out on the other side of the HW cloth I'll have accomplished nothing. Maybe I could cap the tops of the blocks with sheet metal? There'd probly be a lot of chipping and cussing and swearing, trying to knock off gobs of mortar that's squeezed up above the blocks.

Another possibility might be using Tapcon screws to screw the HW cloth down to the cinderblocks. I've used Tapcon screws in solid concrete but not in cinderblocks. I wonder if they're too fragile for that? I'd have to use a lot of Tapcon screws, and they ain't cheap. Maybe a combination of rolling the cloth into the gaps, then covering again with another strip that's screwed to the mobile and to the blocks?

I can't imagine that caulk or foam would work. They'd chew right thru that.

If anyone has some better ideas I'm all ears!

[Greg S]

Mice can fit through a gap less than 1/2" wide and both mice and chipmunks will chew through anything except metal if they have a reason.
Your best and likely the only one that will be completely successful is to use the poison and don't tell your wife.
Chipmunks and squirrels are simply mice and rats with furry tails, tree rats.
They are dirty and cause disease, stink up the house with the smell of urine as well as carrying flees.

[Greg]

HI & welcome. There are a few ways for critters to get in, with out knowing how your's is set up I"ll throw a few ideas out that may or may not apply to you.

Are the blocks on a poured footer? They may be digging under the blocks.
Are there any pipes or wires running through the blocks? If the hole is slightly over sized the could be getting in that way.
Tapcons WILL hold in blocks, pre drill first, You could try flashing. You did not say if the home is sitting tight on the top of the blocks or not, If possible you could run flashing from the INSIDE of the top block over the top of the block and under the back of the hardiboard. That would effectively make a metal barrier between the home & blocks.
Any gaps can be filled with steel wool, push it in as tight as possible.
The other Idea I have would be to cover the blocks with steel sheets (Pole barn type) with the bottom buried in the ground, that would make a complete steel barrier.

Greg

[Telkwa]

The cinderblocks are on a poured footer. It's not a monolithic slab from one corner to the other. It's one continuous pour around the perimeter, and another wide pour down the center. In other words, there are two strips of dirt directly under the two halves of the double-wide where none of the metal support jacks go. There's concrete underneath all the support jacks. We filled the two dirt strips with bottom ash from a coal-fired steam plant. The ash is like gritty sand that packs well and drains well too. I'll have to check where the water and electrical comes in, and the wastewater line goes out. I think the electrical is underneath the footer, and the other two come in just above the footer thru gaps in the cinderblock.

Sorry, I thought all mobile home/cinderblock skirting was done the same way. The mobile was all set up and occupied before the cinderblock went up. The final course is a couple of inches shy of the bottom edge of the mobile. There is no contact between the two.

It's my understanding that this is common practice, at least here in Washington State. I specifically asked about that, because I wanted cinderblock right from the beginning, and I thought that the mobile home rested on the block. Sorta like a "real house". Nope, not the way we do it, is what I was told.

Your suggestion, to attach metal flashing that runs from the inside of the cinderblock, across the gap, and then to the outside, behind the Hardi-Board, sounds very bomb-proof to me. There will be some variation in the gap. For one, the cinderblock is rough, and two, I imagine the cinderblock isn't laser-straight. The cinderblock isn't wobbly to the naked eye, but you know what I mean - tossing up a cinderblock wall that doesn't even touch anything isn't exactly a precision job and they probly didn't take much time to get it down to the last 1/16th". But if we had the flashing bent so that the part going across the blocks was slightly diagonal, instead of having it bent 90 degrees at both turns, I'd think there would be some wiggle-room?

If we were to substitute some heavy duty HW cloth instead of flashing, that would work, wouldn't it? Tapcon it to the inside of the cinderblocks and weave it thru to the outside under the Hardi-Board?

Either way means a lot of work underneath the mobile, which I was hoping to avoid. If I'm gonna spend a bunch of time under the mobile anyway, why not just attach both ends of the flashing or HW cloth while underneath? Do you see any advantage to running the flashing or HW cloth across the gap (from inside bottom to outside top) and attaching behind the Hardi-Board vs. just attaching top and bottom while underneath?

Going across the gap and attaching the upper side of the flashing or HW cloth behind the Hardi-Board seems better to me than attaching from the back/underneath, but I'm not sure why. Plus it'd be more work to tear off all the Hardi-Board. Chances are some of it would break. And I'd have to re-caulk the upper edge. And paint. Oh, well. This has to be done right the first time. It just won't do to cut corners, then find out that they're still getting in.

Today's Sunday but tomorrow I'm gonna start making some calls - to exterminators and the local sheet metal shops - and see if anyone's got any great ideas. Western Washington's got lots of mobiles, and lots of mice, so I'm thinking someone's gone down this road before.

EDIT: What about flashing bent into a deep "V" shape, with two wings at the top of the "V"? Attach to the mobile and the cinderblock with screws thru the wings, and the "V" part would jut into the gap between block and mobile. Something like that could be attached from the front or the back. But attaching on the front would probly push the Hardi-Board out and away, especially any place that the sheetmetal got rippled because of inconsistencies between the two surfaces. "V" shaped flashing or HW cloth would probly have to be done from underneath, eh?

[Greg]

OK, so the blocks offer NO support for the home? Someone missed out on a great parameter blocking start.

As long as there is an air gap (I would not be too wild about) I would go with the Hardware cloth and utilize the ventilation to your advantage. You may want to take some pressure treated 1x and screw through that, then the hardware cloth into the block. You would only need a screw every 18" - 24" to secure it tight to the blocks.

Greg

[Telkwa]

Yeah, I thought it was weird that the mobile doesn't set onto the blocks, but like I said, that's how it's done around here. Or so they said.

Maybe I was being lied to.

Anyway, I'll post back with whatever we decide to do.

[flcruising]

Something we use here to keep out the snakes and rodents are moth balls - though snakes do a good job of keeping away the rodents. Just sprinkle them around underneath.
(Reminds me - I need to do that again under our front porch)

...or you can get yourself a cat.

[bondo]

I too live in WA state and have been dealing with this problem since Oct. I have the same skirting and same situation. My skirting had screen similar to window screen, so the mice walked right through that. Once I sealed that up with metal mesh screen, they kept finding new ways. Finally I had everything blocked except the gap between the block and house. I've been racking my brain for months thinking of a good easy solution. My solution, which I just finished today, is to cut long pieces of wire mesh, fold it to a V shape and stuff it up the sides of the house. It fits pretty snug and doesn't slip due to the rough blocks. I also shot some expanding foam up the sides to help hold the mesh screen. If you just shot expanding foam up the sides that might help, I'm not sure they'd be able to climb vertically and chew the foam out at the same time.

[bondo]

also, if you do use poison, your wife will know. As you're sure to have dead mice down in the crawl space. Whatever you do just be diligent and don't let up, they can do alot of damage.

[Greg S]

It is my personal opinion from having lived in the country that there is no 100% guaranteed method of preventing mice from getting into a home. The best you can hope for is to control there presence.
I built a cottage, myself by hand, and every stage of construction was completed with mice in mind, I left no gapes in the perimeter anywhere to my knowledge. In addition I drywalled every wall and ceiling surface on the interior as well.
Mice got in anyway. I discovered they were climbing straight up the outside wall and pushing up the aluminum soffit at the top of the wall and entering the attic. From there I have no idea how they got inside the house but they did. I tried everything until I finally gave up and put out poison. Within a week there was not a sign of mice and to this day I have not seen another one inside or around the cottage. All I have ever seen is tufts of mouse fur.
Warfarin poison dehydrates the carcases and does not result in any smell.

You could attempt the methods suggested to prevent these B&E specilists from entering your home but I strongly suggest you keep poison as your fall back plan. Trust me you will need it.

[jakehobby1]

also, if you do use poison, your wife will know. As you're sure to have dead mice down in the crawl space. Whatever you do just be diligent and don't let up, they can do alot of damage.

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[Telkwa]

bondo's reply is remarkably similar to where we're at now. I started calling people and ended up setting an appointment with a small outfit from a small town near us that specializes in animal control.

The young man who showed up said our concrete block skirting was installed very nicely, and the overlapping Hardi-Board was very tight to the blocks. The problem is these split blocks are coarse. You can be in contact with the Hardi-Board at one spot, then slide your fingers along and find a 1/2" gap. We discussed drastic measures like removing all the Hardi-Board and installing a wide sheet of HW cloth, but he said the Hardi-Board would break and it'd end up being a big job. He thought he could get good results by simply bending strips of HW cloth into a "V" shape and stuffing it behind the Hardi-Board.

He said that they would also shoot expanding foam into the bigger gaps. I've used foam before. Mice blow right thru it. But he explained that if you shove the HW cloth into the gap first, then apply the foam, the foam expands into the mesh and sets up, creating a barrier that's tougher than just the HW cloth.

So we signed on the dotted line. Problem is, they never used any foam. I asked about it as they were wrapping up and he said the HW cloth fit so snugly that he didn't think they needed it. I'm annoyed that he talked about foaming before we signed, then didn't do it, but I can go around the perimeter with a coupla cans of foam.

We have two openings in the block skirting that allow access under the mobile, with screened wood frames blocking the openings. The animal control guys put heavier HW cloth on both of the frames. I cut up some metal flashing and attached it so that the flashing overlaps the gaps around the frames. The openings are directly underneath two doors on one side of the mobile. They're hidden behind some wood steps. When we first pulled back the wood steps, we found a handsome Northwestern salamander tucked into one of the corners. I scooped it up and released it in between some big rocks along a retaining wall we built a few years ago. My wife and I don't want mice under the house, but we think salamanders are cool

I was worried that the HW cloth would push the Hardi-Board away from the concrete block, but I don't see evidence of that, even at the corners of the house where it would be most evident.

It's too soon to say whether the HW cloth is stopping, or at the very least has drastically slowed down, the rodent traffic. And, as mentioned above, mice are persistent. So I don't think we've necessarily solved the problem once and for all, but at least we've done something about it. Well, paid to have something done about it...