Simple sub-floor (over concrete) question

[David Bonnell]

Hi all,

I recently stumbled on a product that combines 0.5" of extruded polystyrene (XPS) with 5/8" OSB in a 2'x2' panel. It is called Barricade, is rated for 5000 pounds/sq.ft., and is meant to be used directly on top of a concrete floor. There are no additional supports between concrete floor and OSB layer...just the 0.5" layer of XPS.

Question: is there any reason why you couldn't lay down 4'x8' sheets of XPS and 4'x8' sheets of 5/8" OSB to achieve the same result? Again, the XPS would entirely be supporting the layer of OSB. Material cost would be roughly 50% of the assembled 2x2 panels... (~$8 per panel)

[marson]

It looks to me like the barricade is mostly meant to be floating, except for the tapcons around the edges when using tack strip carpet. Also, it is interlocking. 5/8 OSB is not tongue and groove, so the edges would have to be fastened or they would pop up. However, fastening with tapcons would be no huge deal. So in short, no, there isn't any reason you can't come up with your own version.

[David Bonnell]

The biggest concern is if the 1/2" (or 1") layer of XPS would be adequate floor support (instead of 2x sleepers)...but that seems to be a non-issue. I live in a cold environment, so I am astounded that nobody else (that I know of) seems to be taking this approach when building a basement subfloor. People must be looking for ways to save money, I guess....IMO, saving money on insulation only to lose it (repeatedly) in heat loss doesn't make any sense.

[marson]

I wouldn't be concerned about the foam compressing at all. Specify 25 psi extruded polystyrene, the kind used under slabs. . We put 2" of foam under slabs and footings all the time. I have also made a plywood-foam sandwich for insulating a floor, sort of like you are talking about except over wood joists. Worked great. Have even seen

1" foam put under log cabin walls (It compresses to 7/8").