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Raising living room floor using rigid foam

user-5593551's picture

I have a second floor sunken living room that I would like to raise to the surrounding floor level. I am considering using rigid foam board to take up the space and hopefully reduce noise to the living space below. I would place plywood and flooring on top of the rigid foam. The supporting joists are adequate for the additional load.

Are there concerns or code issues with this approach? Would I be better off just taking up the space with 2Xs and adding sound attenuation on the underside?

I'd be a little leery that (post #216349, reply #1 of 4)

I'd be a little leery that the foam would compress over time, leading to squeeks and bounce.

Perhaps the foam manufacturer would share some advice on this application.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Not at all. The foam (post #216349, reply #2 of 4)

Not at all. The foam compressive stength is more than edequate. We frequentlyuse rigid foam beneath concrete slabs that are subjected to vehicular traffic 

But concrete spreads the load (post #216349, reply #3 of 4)

But concrete spreads the load much more evenly than plywood.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

maybe... (post #216349, reply #4 of 4)

It's not unusual to have flooring over plywood over 1" polyiso foam on top of concrete floors. I think 1" Styrofoam actually has a c ompressive load rating. But I don't understand how much you need to raise your floor, probably a limit on how thick the foam can be. I also have seen a sound reduction rating for foam in a floor, it seems like it was impressive. I recently did a small area as described above in a remodel [lam over plywood over foam and it had a good feel to it.

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