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Old 10-19-2021, 09:19 PM   #1
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Insulation thickness and furring strips

Hi guys,

I'm using 1x2 furring strips for my subfloor and didn't think ahead to check the available thicknesses at Home Depot. I ended up having to go with 1" polyiso. This is leaving about a 1/4” gap between the top of the furring strip and the top of the insulation boards (insulation being taller than the furring strips). Should this cause any issues?

I thought about ripping down some of the scrap 1x2's and cutting them into a bunch of spacers that I can glue on top of the furring strips to support the top layer of plywood once I lay that down. Not sure if that is necessary?

Any thoughts would be greatly appreciated!

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Old 10-20-2021, 10:17 AM   #2
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I would add another 1/4"
Rip a 2x4 into slats, rip up all your drops and lay the on the 1x2's.
Tack each slat down just enough to keep it in place until the plywood is on and screwed down.
Besure you use right length plywood screws
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Old 10-20-2021, 11:27 AM   #3
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Originally Posted by Mikethebuilder View Post
Hi guys,

I'm using 1x2 furring strips for my subfloor and didn't think ahead to check the available thicknesses at Home Depot. I ended up having to go with 1" polyiso. This is leaving about a 1/4” gap between the top of the furring strip and the top of the insulation boards (insulation being taller than the furring strips). Should this cause any issues?

I thought about ripping down some of the scrap 1x2's and cutting them into a bunch of spacers that I can glue on top of the furring strips to support the top layer of plywood once I lay that down. Not sure if that is necessary?

Any thoughts would be greatly appreciated!
The issue will be that your screws will pull through your flooring when you try to send them home tight; or, the floor will squeak because the fastener couldn't cinch the two pieces of wood tight.

The fix would be to include a spacer on the furring strips. Could be 1/4" ply or even masonite (I'd stick to plywood). Make sure the furring strips stand proud (higher than) the insulation, otherwise you may see a dip in the finished floor wherever two pieces of subfloor meet.

Best practice is to glue everything down, even if you just use a thin bead of adhesive.
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Old 10-20-2021, 07:12 PM   #4
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You could also put strips of 1/4" XPS foam board on top of your furring strips, which would come up flush with the 1" polyiso. This would provide a bit of a thermal break between the wood of the furring strips and the plywood.
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Old 10-20-2021, 08:12 PM   #5
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You could also put strips of 1/4" XPS foam board on top of your furring strips, which would come up flush with the 1" polyiso. This would provide a bit of a thermal break between the wood of the furring strips and the plywood.

Owens Corning makes a product called Fanfold using their Foamular XPS formula. It comes in 1/4" thickness (R-1) with 10psi compression strength.

It's generally intended for application as a backer board for residing applications where it provides a flat uniform surface.

The price is not bad for the amount of material provided and it's already the correct thickness. One piece is 4'x50' (fan folded).

Insulation Supply is a wholesaler/retailer, located in Ohio.
https://insulation.supply/product/fa...esiding-board/
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Old 10-21-2021, 10:11 PM   #6
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Thanks for the replies! I ended up ripping down some 2x4's and used liquid nails to attach them to the top of the existing furring strips and tacked them down. It seems to have done the trick!
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Old 10-31-2021, 08:34 AM   #7
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My motto:
* Simpler is better.
.
2003, for our ExpeditionVehicle, I set one-inch pink-board on the box floor.
Over that, I set half-inch plywood... painted to seal on all surfaces.
The visible floor is slate in the center, bamboo tongue-n-groove plank around the perimeter.
.
Nearly two decades full-time live-aboard, the pink-board shows zero-zero-zero signs of crush or crumble.
.
If we were Perfessioneral Snowboarder types living in a freezer, I might double that one-inch pink-board.
So far, this is working just fine.
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