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Retired Contractor
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Discussion Starter · #1 ·
Location: Northeast
Winter Concrete Temps: 32* f
Full to Partial Below Grade
No water penetration!

So I'm getting to finish off my basement - finally! It started 12 years ago when I built the house and then stopped, which is a good thing as what we did then and now are a bit different.

So I like the idea of use the 2" Foil Faces Rigid Closed Cell Foam on the walls followed by the furring strip method seen on TOH

My walls were poured well and not wavy at all and we won't be hanging TV's on them since 1/2 of this basement are 1/2 concrete walls and the sections that are full (9') concrete walls are in areas were a TV would never go.

So that brings me to the floor.
I've done tests using 2" foam with plywood over it. One had an air gap and the other did not. The air gap with foil up was a few degrees warmer than the wood in direct contact with the foam. (Foil only matters if you have an air gap)

OK, so now ideally I'd like to put as thick of an insulation down under the floor as I can, but to do this, I'd then have to lay the subfloor right on the rigid insulation. We see this down with Barricade OVRX tile floor system, but I'd want a much thicker insulation system.

So I have three options:
Option 1) PT 2x4 Sleepers laid 24 O/C over a 6mil plastic blanket with 1" rigid foam in between and 3/4" T&G Sub Floor attached to the sleepers. Sleepers float on the floor and do not penetrate the concrete with screws. I end up with a 2,25" thick sub floor and no insulation every 24"

This option means I need to remove and reinstall 2 Glass SLiding Doors to compensate for this thick floor.

Option 2) Lay 3/4" rigid T&G foam down (no vapor barrier) on the floor and cover with 5/8 T&G sub floor screwed to the concrete.

This puts me 1/8" shy of the lip on the Glass Sliding Door. I guess I could drop down to 1/2" rigid Foam Board too.

Option 3) Use a Barricade Flooring system.

This puts me 1/2" under the lip on the Glass Sliding Door.
BUT...since this system remains 1/2" out from the walls, I do not consider it a true vapor barrier.

Next issue!
We plan on covering the subfloor with a laminate flooring. It is recommended that you install the foam pad under this, but won't this create a double vapor barrier?
 

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Sean
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Why not option 3 with full sheets of 1/2 XPS under that - 2" would be better but if you don't want to reset the doors...
As for foam pad used under most floating laminate floors - it is not a closed cell so that point is mute, the laminate can act as one though but if vapor is getting that far up you have other issues
If you are really worried about vapor, apply a one of those crack isolation membrane before you put down the foam & then control the moisture above (relative humidity, etc...)
 

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Retired Contractor
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Discussion Starter · #3 ·
Why not option 3 with full sheets of 1/2 XPS under that - 2" would be better but if you don't want to reset the doors...
As for foam pad used under most floating laminate floors - it is not a closed cell so that point is mute, the laminate can act as one though but if vapor is getting that far up you have other issues
If you are really worried about vapor, apply a one of those crack isolation membrane before you put down the foam & then control the moisture above (relative humidity, etc...)
My concern over that is with the thickness of the wood (kind of thin) over that much rigid board.

I did think about some way to T&G all 4 sides of 3/4" sub floor and then glue it to the rigid foam board.
 

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Retired Contractor
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Discussion Starter · #4 ·
I wonder how well Plywood clips would be over the short end's of 4x8 T&G Sub-flooring?
 

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Sean
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I would worry about plywood clips telegraphing through - as for the foam to laminate question - that shouldn't be a factor as it is over the 3/4 ply which is now the subfloor - as long as any dips, etc... are taken care of & the subfloor is smooth you shouldn't have any issues that I see

If you are worried about connecting the floors together - you can attach with those spring loaded nails - the ones with a slight bow in them (drill through material in question to proper depth, drive nail & move onto next - though you may need to drill a countersink hole also)
 

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Retired Contractor
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Discussion Starter · #6 ·
I would worry about plywood clips telegraphing through - as for the foam to laminate question - that shouldn't be a factor as it is over the 3/4 ply which is now the subfloor - as long as any dips, etc... are taken care of & the subfloor is smooth you shouldn't have any issues that I see

If you are worried about connecting the floors together - you can attach with those spring loaded nails - the ones with a slight bow in them (drill through material in question to proper depth, drive nail & move onto next - though you may need to drill a countersink hole also)
I am more concerned in making sure the short end of the plywood is connected to the short end of the adjoining board.

I've seen reviews on the Barricade flooring site where people are noticing them opening up. Some are now gluing these joints together.

I've been trying to avoid drilling into the sub floor as we do have RADON and we have a Mitigation System installed. Any and every penetration in the floor will reduce the negative vacuum effect. While I might be stretching here, that is my #1 concern with it durectly fastened to the concrete.

If I could get over that, I could drill and screw the 3/4" T&G flooring right to the concrete with the rigid foam sandwiched in between.
 

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Sean
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As long as you are not drilling all the way through the concrete you are not opening up any pathways & even if you did the fastener should block it. the crack isolation membrane should also help seal it out also - at least from the floor. You may also consider finding a way to pressurize that area - maybe an ERV/HRV which pushes air in & pulls from higher up the house (be cool if they offered one with a slightly oversized fan for the intake side)
 

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Retired Contractor
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Discussion Starter · #8 ·
As long as you are not drilling all the way through the concrete you are not opening up any pathways & even if you did the fastener should block it. the crack isolation membrane should also help seal it out also - at least from the floor. You may also consider finding a way to pressurize that area - maybe an ERV/HRV which pushes air in & pulls from higher up the house (be cool if they offered one with a slightly oversized fan for the intake side)
There is a Mitigation System down there now which creates a negative pressure under the slab. We sealed every crack, hole and cut to insure proper operation of the system. Since its a forced hot air system, I think that to does pressurize it "slightly"

I think you are right though. As long as I don't go through the concrete, I should be OK.

So that would mean I could go with a 3/4" rigid foam, taped and sealed - topped with 5/8" T&G screwed down on the short ends and perhaps a few screws on the long ends too. I'm thinking I might want to upgrade to 3/4" flooring as there will be a pool table down there. Since I have time...I might just do an experiment and put down a sheet of 5/8 T&G over 3/4 Foam and see what happens as I work on the walls.
 
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