PSI of underslab insulation?

[socapots]

Ok.
so another question that has come up in my mind..
How do you know how strong the insulation under your slab should be?
I tried searching the forums a bit but didnt come up with anything that says what people used and why.
If i am wrong and the threads are out there please point me in the direction and it would be greatly appreciated.
The shop i build will be parking for a truck, as well as have an area for a lift.
Do i really need to worry about the strenght of the insulation i am putting under there?
Any help/input is appreciated as always.

 

[matouse3]

Here is one thread with the discussion.

http://www.garagejournal.com/forum/showthread.php?t=164230&page=2

Most of the threads related to this topic are in the Heating/AC forum, not the flooring.

From what I have come across on here, the most agreed upon (but this is not across the board) is the use of 2", 25psi XPS pink/blue board. This stuff runs about $20-$30+ per sheet. Other on here have used EPS and door cutouts (if you have a supply around you) with out an issue. I personally put down the 2" XPS 25psi.

 

[socapots]

Thanks for the response.
I was kinda wondering if I was posting in the right area. Lol.

 

[rburke65]

I used the white styrofoam under my floor. PSI rating.......? Don't know. I got it free from a local insulating contractor when they were installing a new roof and updating the insulation on local high school. They were giving it away. In know from my previous employment that this had to have been 15psi +-. in my opinion, you really do not need the 25 psi board. This has been talked to death here on TGJ. Placed my floor in Aug. of this year, atop of a good base, no cracks. Good luck.

 

[socapots]

Thanks man. I'm still looking for some good topics. Gotta try some different search methods I think. If anyone remembers the name of a tpoic let a guy now.
Thanks.

 

[51rider]

I cannot recall any threads specifically, but the key to any underslab insulation is its compressive strength. This is measured in Pascals (Pa) & generally the higher the figure the better.
For example, the 50mm (2")board I used has a compressive strength of 350KPa (KiloPascals). That figure isi roughly around 50PSI.
I won't give you the name as I don't think it is available on your side of the pond.
More recent thinking is that 75mm or 3" is the minimum amount of insulation you want if installing directly above grade and below the slab. If you already have a structural floor slab in place, then 50mm or 2" of insulation below the finish floor slab is the minimum you want to go for.
Try this link, URL]
for further information.