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Princelake
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# Posted: 15 Jan 2022 08:34am
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Hey guys, just brain storming and planning for spring. My cabin is on piers ranging from 2-4ft off the ground. The ground is all bedrock so minimal moisture. I plan on putting batt insulation between the floor joists. Now to protect it from mice, insects, and moisture. Other camps in the area have just put 7/16†osb. Will that hold up? Spend a bit more and put 3/8†plywood? Mice can chew through wood. I was thinking house wrap and 1/4†wire mesh.
https://www.homedepot.ca/product/fencer-wire-1-4-inch-x-4-ft-x-100-ft-23-gauge-hardwa re-cloth/1001469451
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travellerw
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# Posted: 15 Jan 2022 09:29am - Edited by: travellerw
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I have thought of these same issues.. Mice are persistent and will find any little hole, then leave a pee trail so other mice can follow. In the end I came to the conclusion that the only %100 solution was to keep the insulation on the inside.
Mine will be insulated with 2" foam on the inside, then a 5/8" subfloor over that. However thats usually not an option unless you planned for it during the build.
I think a better solution if you didn't plan for an insulation subfloor, is rigid foam between the floor joists. Its way more work, but mice seem to like it less. It doesn't make a nice warm cavern full of nesting material!
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rpe
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# Posted: 15 Jan 2022 09:29am - Edited by: rpe
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That's exactly what we used. We have had no critter issues.
TSC (now Peavy) puts that 1/4" mesh on sale regularly for a significant discount. Keep an eye out if you have the time.
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gcrank1
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# Posted: 15 Jan 2022 10:49am
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Having done some remodeling and demolition Ive found mouse nests and trails in batt insul., I dont think it is the right stuff for that application especially without enclosure.
Having done blue DOW 1" sheet insul in '83 between the joist before the decking I can say we never had issues from below; it was exposed beneath.
Now Id be inclined to repeat that with 2". I think they make it pre-cut for between 16" and 24" centers? I had to cut my own 
OR, probably the smart way, put down a 'base decking', top with the 2" eps then the heavy floor decking.
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Princelake
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# Posted: 15 Jan 2022 11:02am
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I did not put Ridgid foam insulation under my floor decking because it only has R-10. Right now it’s currently -34c at camp. Batt insulation gives the highest R value for the best price. 4’x8’x2†sheets of ridgid foam are over $40 a sheet here.
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kevlar
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# Posted: 15 Jan 2022 11:14am
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I'm building a small cabin on a trailer this winter, I'm going with fiberglass insulation with 1/4 inch hardware cloth, all the research I did said that should keep mice and squirrels out. They will just eventually chew through any kind of wood given enough time. I hope it works, I got some from Peavey Mart a week ago on sale.
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Brettny
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# Posted: 15 Jan 2022 11:33am
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What's the cost difference between 2in foam and fiberglass with hardware cloth or plywood? It may be less than you think. Ontop of it the foam is a far better product.
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Brettny
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# Posted: 15 Jan 2022 11:43am
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You should really use some type of tyvex or house wrap on the outside of the insulation. Paper faced stuff will nearly be useless in a few years.
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gcrank1
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# Posted: 15 Jan 2022 01:03pm - Edited by: gcrank1
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That and the paper/vapor barrier side is supposed to go to the warm side.
Was it somebody here that put ledger strips way down in the floor joists, cut and fit 1/4" luan, then paper faced batts stapled in from the top side? (just like doing a studded wall laying down)
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Princelake
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# Posted: 15 Jan 2022 02:17pm
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You can’t even buy paper faced insulation in northern Ontario.
Maybe batt insulation followed by a layer of ridgid below it.
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toyota_mdt_tech
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# Posted: 15 Jan 2022 02:53pm
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Quoting: rpe That's exactly what we used. We have had no critter issues.
Bingo, and a nice little air powered crown stapler can be used to secure it to the rim joist so they dont try to enter under the ends, and if they try, metal flashing, just a flat roll of the stuff and secure it with the same crown stapler.
I used a full footing/stemwall with no exterior crawlspace access, my vents have the same sized screen mesh. No varmints.... well, not a woodpecker, but I think I took car of him and didnt even have to kill it. 
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kevlar
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# Posted: 15 Jan 2022 04:05pm
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Just did a quick price comparison, to get the same R value, the foam board would be close to 3x the cost. I forgot to mention I will put house wrap in there as well, vapor barrier on top. Can't even get fiberglass with the paper backing here anymore. Have seen squirrels destroy foam board I had sitting in a barn, so doubt that would keep them out. Spray foam would be best, but that much more money again.
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travellerw
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# Posted: 15 Jan 2022 04:21pm
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Quoting: Princelake I did not put Ridgid foam insulation under my floor decking because it only has R-10. Right now it’s currently -34c at camp. Batt insulation gives the highest R value for the best price. 4’x8’x2†sheets of ridgid foam are over $40 a sheet here
If you check my other posts.. I stayed in our cabin recently at -40C (northern Alberta). We don't have the floor insulation down yet (so just 3/4 OSB) and it wasn't all that bad. R20 will be more than enough for the floor! Even without it, we were able to maintain the cabin at 17-22C with the wood burner on the lowest damper setting.
I think no matter what you do on the outside, them suckers will get in. I have literally spent 10 years trying to seal up my trailer belly to keep them out. 10 years and I'm still fighting a loosing battle. I tried screens, spray foam, steel wool, tape, ect... Chewed through most of it.. They make a spray foam with poison in it that I have been considering, but hate the idea as it may poison animals I did not intend to.
Good luck.. I hope you find something that works.
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travellerw
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# Posted: 15 Jan 2022 04:23pm - Edited by: travellerw
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P.S. Watch the used market (facebook and kijiji).. Often big projects buy too much foam insulation and then dump it on the used market. I bought mine for less than 1/2 what HomeDepot wanted for it!
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paulz
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# Posted: 15 Jan 2022 05:40pm
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Nothing to do with insulation but I've been getting free onions and garlic and tossing them under the cabin. Supposed to repel mice and varmints. Don't know if it works, they're probably making a pizza down there.
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gcrank1
Member
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# Posted: 15 Jan 2022 05:57pm
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Garlic will keep the vampires away, not sure what the onions will do, maybe take root?
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rpe
Member
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# Posted: 15 Jan 2022 08:05pm
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Quoting: travellerw P.S. Watch the used market (facebook and kijiji).. Often big projects buy too much foam insulation and then dump it on the used market. I bought mine for less than 1/2 what HomeDepot wanted for it!
Same applies to batt insulation! We got a trailer load of R22 Rockwool batts (~16 bundles) for less than half new, and no tax to boot. They were on the jobsite, and got splatted with plaster mud and goobers of spray foam, and couldn't be returned for refund.
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arp
Member
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# Posted: 15 Jan 2022 09:22pm
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I sandwiched Reflectix (bubble foil) between the joists and plywood decking when I built my 10x16 bunkie.
I've seen it done with success from a few youtube channels I follow. You can also add it in the joist cavities after the decking is down if you can access it. Make sure it wraps down the joists by a few inches and tape the joints with foil tape. Chipmunks and other critters don't like the foil and don't seem to chew through it. Doesn't give much R value but I did alright in there with a heater and rockwool in the 2x4 walls at -30*C
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Brettny
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# Posted: 16 Jan 2022 05:27am
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We have a foam factory a county away that sells "scratch and dent" foam. Typicaly these are various thickness 4x8x4' pallets for $50. The used market costs more than getting it direct.
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Steve_S
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# Posted: 16 Jan 2022 05:44am - Edited by: Steve_S
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Quoting: Princelake My cabin is on piers ranging from 2-4ft off the ground. The ground is all bedrock so minimal moisture.
Do always keep in mind the moisture & humidity under the cabin, bedrock exposed or not. If you intend to put any OSB or whatever up to enclose the floor base, do pre-treat it & prep it properly before insalling it. After a few short years OSB will start to swell & separate and Ply can start to delaminate... A Can of treatment is cheap and smart thinking.
Piers.
That is the access path for rodents, you can put aluminum shields around the Posts and even a Guard Cap to prevent rodents from climbing up the posts such as this below. Making it harder for them to climb up to the structure is not that hard.
Insulation Process, just my thoughts.
- Install Building Wrap onto the joists, then the Treated sheathing material. Make sure everything is sealed, especially around any pipes etc.
- Use a "Spray Foam Kit" (Non Soya !) and spray in 1 inch, making sure to get all the nooks and everything is sealed.
- Then use Roxul Batt to complete the insulation fill between the Joists.
- Next lay down a heavy 6mil+ plastic, sealing it to the joists with "Acousti-Seal", and then lay your subfloor.
https://www.lepage.ca/en/lepage-products/build-things/sealant/pl-construction-sealant /pl_acousti-seal_vapourbarriersoundreductionadhesive.html
You have not mentioned how the plumbing etc is being done, if through floor or out a side wall or what. This can sometimes be a "critter highway" as well. The chipmunks up here got Damned Creative ! Never underestimate motivated beasts !, Aluminum shields & guard do work a treat around any plumbing access points. The little bugger only need one "TINY" spot where they can start to gnaw a hole.
I watched field mice squeeze through a 3/8" Hole with little difficulty! Chipmunks can get through a 1/2 hole...., ruddy blighters, a MENACE !
Do keep an eye on Kijiji for Foam Insulation Sheets, they do come up, over stock or overbuys are common as is surplus. That is where I found the commercial roofers who supplied al of my foams.
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rpe
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# Posted: 16 Jan 2022 08:34am
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My cottage neighbour fit eps foam sheets in his joist cavities. They ended up coming loose over time, and the mice made nests between the foam and the floor sheeting. On a quiet evening he could listen to them racing back and forth in the joist bays below his feet. He had a spray foam company come and they offered to spray foam from the underside, sealing the the existing eps (and mice!) into the joist bays forever. I've heard very good results with the spray foam option as well.
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gcrank1
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# Posted: 16 Jan 2022 09:22am
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That is why it is better to 'do it from the top' than as an afterthought from below.
I put ledger strips in using a simple diy T guide (1" styro, 1" drop off the T) for the styro to sit on, then decked it. Never had any sounds from below.
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Brettny
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# Posted: 16 Jan 2022 11:50am
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Quoting: rpe My cottage neighbour fit eps foam sheets in his joist cavities. They ended up coming loose over time, and the mice made nests between the foam and the floor sheeting. On a quiet evening he could listen to them racing back and forth in the joist bays below his feet. He had a spray foam company come and they offered to spray foam from the underside, sealing the the existing eps (and mice!) into the joist bays forever. I've heard very good results with the spray foam option as well.
Did they just nail up the foam? If it's right at the bottom of the subfloor there wouldnt be a highway. Caned spray foam really holds in foam board in tight and seals it up good.
If the interior of the subfloor isnt finished I would put a few nails right down through in each bay. Then fit your foam in the bay from the underside and push it into the nails. This will hold it and make useing caned foam prety easy.
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rpe
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# Posted: 16 Jan 2022 12:56pm
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Quoting: Brettny Did they just nail up the foam? If it's right at the bottom of the subfloor there wouldnt be a highway. Caned spray foam really holds in foam board in tight and seals it up good.
The one cottage I looked at did have the sheets held up with furring strips, but over the years, the little *&^*@#$'s got up inside and started chewing. There was bits of white EPS all over, and once those critters start living up there, waste, food storage, etc, pops those sheets loose, and it's game over.
I agree with gcrank, planning ahead is always preferred, not possible when upgrading existing structures. One neighbour of mine ended up with major reno a couple years back. He pulled his entire floor decking up from inside the cottage, nailed those sheet metal angle sections that support hanging ceilings along the bottom of each joist. He then ripped sheets of 1/4" ply to fit the gap, dropped them in to sit on those angles at the bottom of the joists, and called the spray foam company to come and fill 'er up. Now that will be an air-tight floor, and likely a better quality job than when the installers are crawling around under the structure trying to aim the nozzle the correct direction.
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Princelake
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# Posted: 16 Jan 2022 01:17pm
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When I framed it I thought about putting down ridgid board before plywood. I question the life span of ridgid foam. I want my cabin to stand 100+ years. In 20-30 years will it deteriorate? I’ve seen rodents make tunnels in ridgid foam and spray foam. I feel I could make a huge mess for myself down the road. I kept the camp up high end to insulate underneath it.
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gcrank1
Member
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# Posted: 16 Jan 2022 03:04pm
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We did ours in 1983, still good. Underneath, between the joists it is not exposed to sun and weathering at all.
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Brettny
Member
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# Posted: 16 Jan 2022 04:28pm
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Quoting: rpe There was bits of white EPS all over, and once those critters start living up there, waste, food storage, etc, pops those sheets loose, and it's game over.
The white styrofoam type stuff? That's terrible foamboard. Everything chews it and can burrow in it, even carpenter ants.
If your putting foam above the sub floor it's not put under the walls. So removing it if needed isnt to terrible.
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gcrank1
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# Posted: 16 Jan 2022 05:19pm
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Beadboard? The cheapest ugly stuff that breaks up into little floating beads that go everywhere and have enough static that they run away as you try to catch them? Horrible YES, I dont even like it for packaging.
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rpe
Member
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# Posted: 16 Jan 2022 06:41pm
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Yeah, what the guy had used was beadboard. He went to a fair bit of work too, fitting it up between the joists that weren't all perfect 16" centers. Once that stuff is loose with easy air movement around it, I think the effective R value drops to near zero.
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gcrank1
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# Posted: 16 Jan 2022 07:11pm
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Even if put in tight with no gaps the R Value is low. Sad thing is it took as much work to put in that poor stuff as it would have to use good stuff.
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