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ram1500 10-14-2012 12:31 PM

XPS HD PSI for above concrete slab
New here but was wonder what you think of placing a 1" XPS foam on floor then 6-10mil poly then 13-15mil laminate on a basement subfloor for 1500 sq ft.

For the 1" XPS stores have 15, but can special order 25-100 PSI.

I would like to avoid adding 1/2 or 3/4 OSB for height reasons.

Been told 15 PSI would be risky of compression but 40-100 PSI would be fine since both foam and laminate will be floating.

I noticed is there are the 4x8 products (anything higher that 15 PSI is special order) and there are also the 2x2 products as well but hard to find. Here are links to each (both are R5 with 60 PSI).

BTW, I live in southern Ontario Canada and house is 10 yrs old, dry concrete with 24RSI 2lb spray foam on wall and headers. Basement will be used as an office and rec area. More of an open concept.

Not sure what the prices are for higher PSI sheets but 2x2 are about $6 each square, while 4x8 PSI is about $18. Still waiting for prices for 60 PSI.

Wondering what you think the XPS PSI should be and is it worth ordering the 2x2 or 4x8 sheets?

Thanks in advance.

gregzoll 10-14-2012 12:34 PM

You would be better to lay a sub floor over the XPS. What is the current height. from floor to joists for the main floor?

ram1500 10-14-2012 12:52 PM

Walls and ceilings are already have drywall and primed.

Since this is a basement we have bulkheads around ducts. Under bulk heads is about 79 1/2" high otherwise everywhere else is 90".

As an FYI, bulk head is bout 5ft wide right in the middle of house. Kinda large IMO but there wasn't a choice.

My wife suffers from raynauld's, poor blood circulation in the hands/feet, so it has to be warm.

We will be adding a gas fireplace as well if that helps.

gregzoll 10-14-2012 08:51 PM

Your best bet is to use either heat under the flooring, or baseboard rad's, and forgive the xps on the floor. As long as you keep the air moving down there and heat when you are in the space, you will be fine. Personally I hate being in a basement for anything, unless I have to be down there to do something.

It is more of getting the walls insulated, is going to be your best bet, other than trying to put a bunch of work into effort on the floor.

At a little over 6 1/2 feet at the lowest point, and 7 1/2 at the highest, your basement is actually about the same as ours. I have to stoop to get under the duct work above our furnace. due to I am 6'-4".

Gary in WA 10-14-2012 09:32 PM

The psi depends on the furniture planned... I usually site this at 36# or 5200#ft.2;

Here are some other foams/floors:

Were you looking to heat it?


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