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Anybody see the article in Fine Homebuilding about basement finishing using 2 layers of plywood over rigid foam board layed directly on the slab?

They layed the rigid foam boards directly on the slab, then topconed the first layer of plywood over the foam and then screwed the second layer of plywood perpendicular to the 1st layer.

They framed the walls putting the sill plates on the new subfloor.

What do you all think of that?
 

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Didnt see it but did they attatch the plates solidly to the concrete? And I would be interested in knowing how they would combat moisture if hardwood flooring was used.
I always shyed away from slab building unless I just had to, but mainly cause I never understood how to develope a fail safe subfloor, so this method is of intrest to me. A slab definitely saves you money.
 

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That's a good question about the wall framing, I assume they would go into the slab with tapcons but maybe not.

I believe there was no moisture issue, I think one of the benefits of the system was the rigid foam eliminated any moisture from penetrating the subfloor so any floor finish was now possible.
 

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The OP stated that the plates went on the new floor, not to the concrete. I would think as long as none of the new walls are bearing walls it should be ok. My only concern would be the foam having a natural tendancy to constantly compact, I could be wrong seeing how there isn't realy any real weight on them. I would still say over time it's going to haunt them, the foam compress's then the screws will stick up?
 

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The OP stated that the plates went on the new floor, not to the concrete. I would think as long as none of the new walls are bearing walls it should be ok. My only concern would be the foam having a natural tendancy to constantly compact, I could be wrong seeing how there isn't realy any real weight on them. I would still say over time it's going to haunt them, the foam compress's then the screws will stick up?
I bet they used foamular or dow board as you won't get the problem of compaction.
 

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what about ceiling height? Remodels might be tough.

I know our PM hems and haws about how many block courses, ridge heights, and over digs......It's probably not an issue, but raising the floor caught my attention.
 

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I've never done it, but I have seen where they have. They lined the walls and slab both with rigid roam. Then put plywood over the foam and studded on top of it.
 

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If the foam's an inch thick it would quite possibly pass code for the 1" expansion required between walls and floor joist. We currently lay a 1" foam on top of the treated plate then set the studs on top ( in basments ) Its quick, and passes code.
 

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I randomly caught an episode of Holmes on Homes (don't normally watch him) where he lined an entire basement that was having moisture problems with 1" foam. He secured the foam with adhesive, siliconed the seams and then covered them with fenestration tape. I figured moisture would eventually find a way in, but it seemed to work for him.

With 2 layers of subfloor, you'd have a pretty sturdy base to attach your walls to, and little to no deflection. I doubt they'd fly for a load bearing wall, but depending on the foam and manufacturer specs, who knows?
 

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I think its a great way to remodel a basement. It typically is going to cost more because your buying the foam and then your going to spend more on flooring typically. When you just go over a slab your typically laying tile or carpet. The other thing I like is your floor should be warmer because your not standing on a slab down there.
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Framer53 said:
I bet they used foamular or dow board as you won't get the problem of compaction.
And the plywood helps distribute the weight over the foam, no load bearing walls on-top of this sub I trust?, don't think it will stand up to that, and the loss of ceiling hight was this a issue ?
 

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I've installed a couple of basements now with a rigid drainage board (ie miradrain) and exterior grade 1/2 ply tapcon'd to the concrete. Creates a thermal/moisture break with minimum headroom loss. Also 1/2 the cost of the dri-core product and is installed quicker too.

I've only had carpet and laminate installed over it - wouldn't recommend tile on that assembly unless the floor is dead flat. Perimeter walls installed on the ply, partition walls direct to the concrete, with poly taped to the drainage board.

Great system - if I had more headroom I would definitely try the rigid sm and ply mentioned by the OP. There's high density/low compaction stuff available if the HO wants to spend the $$.
 

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Sar-Con said:
I've installed a couple of basements now with a rigid drainage board (ie miradrain) and exterior grade 1/2 ply tapcon'd to the concrete. Creates a thermal/moisture break with minimum headroom loss. Also 1/2 the cost of the dri-core product and is installed quicker too.

I've only had carpet and laminate installed over it - wouldn't recommend tile on that assembly unless the floor is dead flat. Perimeter walls installed on the ply, partition walls direct to the concrete, with poly taped to the drainage board.

Great system - if I had more headroom I would definitely try the rigid sm and ply mentioned by the OP. There's high density/low compaction stuff available if the HO wants to spend the $$.
How thick is is the foam ?
 
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