Do I seal/caulk/cement big gaps between foundation and fiber cement board siding?

Submitted by metalmayhem9 t3_10lbdgk in DIY

I am having a mice problem this winter. I did not have them last winter. I would like to figure out ways to prevent them coming in. I found gaps between the fiber cement siding and the foundation (images below). No other cracks elsewhere.

Somebody told me to seal any and every gap like this. But I also heard that these gaps should stay because water needs to come out. How can I safely remove these entry points without endangering the integrity of the structure? Please advise.

 

Probably ok https://imgur.com/smHps2m
Not ok--how do I close this? https://imgur.com/Kp5OwFk
Safe to seal this gap? https://imgur.com/peoQEyn

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PinchePoderes t1_j5w2zmo wrote

I’m not a siding guy so I couldn’t say for sure but in general you’d have a siding, moisture barrier, sheathing, framing/insulation, probably another vapor barrier, then sheetrock, so if mice were getting in under your siding I would expect to see some kind of holes in your interior, that’s where I would look and I’d spray foam it. It’s just kind of a lot of layers for them to go through, not to say that they couldn’t but I’ve more commonly seen them get through areas around windows and doors. I have seen where they will come through siding and nest in the walls.

If you have a crawl space with ductwork in it I’d check around there too. If there is a gap between the duct and subfloor they could probably squeeze through the floor register.

Edit: the other pictures with the cracked foundation could be patched with a concrete epoxy or a concrete patch and repair mix like quickcrete. The picture where you can see 2x4 looks like your bottom plate and you could take a sealant like NP1 rated for exterior use to it. I’d try to lay a bead of it between the bottom plate, sheathing, and foundation rather than the siding. The siding probably does need to breath to eliminate moisture but I would also say due to the technique used to install the siding it shouldn’t see much; assuming it was done correctly. Basically it’s overlapped like that so water runs down and off.

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metalmayhem9 OP t1_j5wnf6w wrote

Thank you so much for the detailed explanation. As for the last picture, I could not see (perhaps due to a lack of experience) any sheathing around the bottom plate. Is it possible that there is no sheathing or sheathing that degraded over /the years?

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PinchePoderes t1_j5wpqx0 wrote

Absolutely, happy to help.

It’s really hard to tell from the picture, but the only time I’ve not seen sheathing used was on a shed and screened in porch, stuff that doesn’t really matter too much. I would be really surprised if there wasn’t any. I’m not am engineer, so I can’t say for sure, but I was always told the sheathing does provide a bit of rigidity and shear strength to the structure.

Sheathing is typically OSB so it is possible that it was a weak spot that crumbled out or the builder just cut it a bit short, that wouldn’t be a super weird thing to see and probably the most likely. It also depends on how old the house is. I actually don’t know when they first started using OSB or Plywood as sheathing but it could be completely different if its pretty old, I’ve seen a couple houses built circa 1910 that just had boards. If you’re really gentle with the siding, you might be able to pull it back a bit to get a better look.

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metalmayhem9 OP t1_j60f0aj wrote

You were right. A sheathing appears to be there. Also some noticeable gaps between the foundation and the bottom plate. Next up is to lay a bead. Thanks!.

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PinchePoderes t1_j5ws4wn wrote

Could be the sill plate. the sill plate sits on top of the foundation depending on the style. Kinda depends what style the builder did and how old it is. It’s really hard to tell without being able to look at it myself. I would still probably try to peel back some of the siding to get a better look.

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OldEEAP t1_j5xg5xs wrote

We have had similar gaps in siding at some of the family rentals. Not sure how big the total number of cracks are, but stuffing it with brass wool has kept rodents out in the past for us.

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metalmayhem9 OP t1_j60f89u wrote

Hmm using brass wool is a new concept to me but it sounds easy enough. TY.

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01lexpl t1_j5yn3nv wrote

I'm in a townhouse, so two areas (and the biggest being the backyard). I bought a roll of copper mesh (on Amazon), folded it over and stuffed it under my siding.

I used my little snake camera to see where there are possible gaps. Found a few where the fuckers could climb in, but they were coming up thru the window - as a small area was kissing spray foam.

In the larger holes like your picture (and on corners), i put the mesh and sealed it off with spray foam. The tighter spots I left the mesh, as it was held in palace tightly by the siding.

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metalmayhem9 OP t1_j60fkv2 wrote

Thank you for the idea. Do you know whether using the spray foam hindered the flow of water? You know, just in case should any end up inside the siding during rain/storm.

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01lexpl t1_j61ti95 wrote

Doubt it. I just added some where it was missing by the window and edges where there isn't much water run-off. I don't have a pic, but my siding goes over top of the foundation more than yours, but it still fine. You're filling in big gaps with foam, and other small gaps are just fitted with copper mesh.

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