Polyiso HD cover board to insulate a basement floor
I need every inch of height on my basement ceiling, so I was wondering if either 1 or 2 layers of roofing type polyiso HD cover board would work as both the insulation and sub-tile floor? A couple of companies make such cover board and both claim an R value of 2.5 for only 1/2" thickness. All input is appreciated.
Asked by Brian Winke
Posted Wed, 11/14/2012 - 01:38
Edited Wed, 11/14/2012 - 01:52
Posted Wed, 11/14/2012 - 01:38
Edited Wed, 11/14/2012 - 01:52
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Brian,
My guess is that the foam will be too squishy to work as a substrate for tile.
My advice: (a) use XPS, not polyiso, (b) include a subfloor of plywood or cement backerboard above the XPS, and (c) choose a more flexible type of flooring -- not tile.
Posted Wed, 11/14/2012 - 07:17
Thanks Martin. I was thinking that cover board was inherently not squishy. To confirm we're talking about the same thing, I'm attaching the following link. There is at least one other manufacturer with a similar cover board, but this will give you the idea: http://www.firestonebpco.com/roofing/insulation/coverboards/isogardhd/
Posted Wed, 11/14/2012 - 08:53
Brian,
Just because an insulation board is stiff and rigid enough for roofing applications, doesn't mean that it's stiff and rigid enough to use under ceramic tile.
Posted Wed, 11/14/2012 - 09:36
Fair enough. Thanks.
Posted Wed, 11/14/2012 - 09:41
There's also the issue that in an over-slab application it's likely to take on groundwater over time, reducing it's effective R-value. Iso is oftenOK to use on basement walls, slabs, not so much (no matter how rigid the subflooring is for distributing the mechanical loads.)
Posted Wed, 11/14/2012 - 13:34
Conceeded and appreciated. Thanks!
Posted Fri, 11/16/2012 - 02:39