Rigid Insualtion Under Slab
Rigid Insualtion Under Slab
(OP)
I am working on a "oh, by the way" project, you know, the ones where the client says,"oh, by the way, we are going to be doing xyz and I hope you are OK with this".
In this instance, the client is going to be putting 60psi compressive strength rigid insulation under the slab on grade and is asking me if this is OK. While this would normally raise a few eyebrows on my end, in this instance, we have some large moving loads on the slab and I am a bit worried about it. The slab was designed in accordance with the geotechnical report which gave a subgrade modulus of 200pci. I can't seem to find anything that will list either a subgrade modulus for the rigid insualtion or an equivalent E value.
Of course I am also getting the "we did it on a similar project so I don't get why you are so worried about this" from the client as well.
Does anyone have experience with adding rigid under a slab on grade?
In this instance, the client is going to be putting 60psi compressive strength rigid insulation under the slab on grade and is asking me if this is OK. While this would normally raise a few eyebrows on my end, in this instance, we have some large moving loads on the slab and I am a bit worried about it. The slab was designed in accordance with the geotechnical report which gave a subgrade modulus of 200pci. I can't seem to find anything that will list either a subgrade modulus for the rigid insualtion or an equivalent E value.
Of course I am also getting the "we did it on a similar project so I don't get why you are so worried about this" from the client as well.
Does anyone have experience with adding rigid under a slab on grade?






RE: Rigid Insualtion Under Slab
http://msdssearch.dow.com/PublishedLiteratureDOWCO...
It provides this table with compressive modulus values that vary between 1,400 psi to 3,700 psi.
For a 1 ft. x 1 ft. area, and an 8” thickness of insulation, that equates to a stiffness of between 25 kips/in to 67 kips/in.
Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies
RE: Rigid Insualtion Under Slab
With this table showing K values for various thicknesses of insulation:
Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies
RE: Rigid Insualtion Under Slab
I had a foam "BTW" the other day on a house I am working on. "BTW, we are cladding the house in 1 1/2" foam and 7/4 (yes 7/4!) reverse board and batten. Tell us how to fasten it!"
RE: Rigid Insualtion Under Slab
RE: Rigid Insualtion Under Slab
Dik