Recently I asked the group for advice about building a house with a cement slab floor. Many responses pointed out that concrete floors are tough on the legs and back. With that in mind, I developed the following idea to make the concrete floor more human-friendly.
– cover the concrete floor with 4×8 panels of rigid insulation 1″ thick.
– cut a 4″x4″ square out of the insulation at each corner where the panels meet, as well as on the edges 4′ from the ends and also in the very center of each panel.
– into each hole place a 1″ thick wood block that just fits into the square hole.
– now cover the entire floor with T&G plywood. The plywood rests directly on the insulation and on the square blocks.
The trick is that the plywood floor “floats” on top of the insulation, and the small wood blocks serve as additional support. The plywood floor could actually be removed if needed, as no fasteners are used.
Has anyone heard of such a system before? Can you see any drawbacks (other than having to undercut doors, etc).
Regards
Paul
Replies
It would work but I'm not sure I understand the reasoning behind the wood blocks. The foam can support a lot of weight assuming you're using a decent thickness of plywood so there are no point-loads on the foam.
I'd be a bit concerned about the edges of the plywood catching a shoe if they didn't stay perfectly flat.
You could always try using pocket screws on the plywood edges.
Since the plywood is tongue and groove, the edges shouldn't pucker.
Without any fastenings I don't see it staying all that flat, at least if we are talking cdx. maybe if you are using advantech or a similiar product. The ends may still be an issue as there is no tongu and groov there. Have you considered sleepers with foam between them.
I don't think the blocks add anything. Why don't you want to screw down the floor through the foam? That is what is commonly done when insulating similar floors in basements.
Skip the wood blocks. Use two layers of ply, staggered joints, screwed togerther.
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Put down 1x4 sleepers, 16" on center. Lay 3/4 plywood perpendicular to the sleepers and then lay the wood flooring.
You're trying to re-invent the wheel, which can be interesting, intellectual fun on the drawing board...but it's not very practical.
Yes, your system would probably work well enough for finish floors of carpet or linoleum, but wood-strip flooring nailed to floating plywood would probably work itself loose over time, and you would certainly never be able to lay tile or stone on it...not would any future owner. That could be a problem when it comes time to sell the place.
Just put down sleepers and screw your plywood subfloor to that. It's simpler, much less expensive (foam-board insulation isn't cheap, you know), and it works.
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Use this instead
http://www.dricore.com/en/eIndex.aspx
What everyone else said....
And also, if you use the blocks of wood, and either the foam compresses slightly, or there are any dips and valleys in the floor you might hear nice "clack, clack" sounds as the small wood pieces hit the concrete when you walk over the floor.
I don't like "clack, clack" sounds.
Paul
No need to insert the blocks
Use spray foam adhesive to glue the foam down to the crete, then do the same gluing the plywood to the foam. do two plies of 1/2" ply and alternate all joints.
The only problem with this is that if you use radiant heat in the slab, it will make it less efficient by far. So if you go that option, just glue sleepers to the slab @ 16" OC, then run the subfloor on those to get a comfortable wood base under you.
edit - the glued down foam and ply layers solves all the potential problems others have mentioned here. use sq edge underlayment rather than T&G - much easier.
You would need to weight each piece down as the glue kicks for about 20-30 minutes.
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Edited 7/24/2009 5:56 am ET by Piffin