Slab on grade on High Density Foam

[EngDM]

Hey all,

I am needing to check an existing slab for a new mezzanine line load, but the slab is on a HD40 (psi) foam insulation and I'm not sure what to take as the subgrade reaction modulus since that is in pcf.

My thought is that I'd need to check the HD40 to support the load, and then check the granular below the foam with a wider footprint since the load will get spread out by the high density foam.

The load is pretty light so I can't imagine there will be any issues, but it is something I'd like to know how to check.

 

[jhnblgr]

https://www.dupont.com/content/dam/dupont/amer/us/en/performance-building-solutions/public/documents/en/styrofoam-brand-highload-40-60-and-100-pis-43-d100994-enNA.pdf

At the bottom it says for static loads 3:1

Nys dot says 1% but I think that’s a but extreme you’re better off cutting it out at that.

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-repository/GEM-24b.pdf

This may or not be of any help: https://www.wbdg.org/FFC/DOD/UFC/ufc_3_220_20_2025.pdf

 

[EngDM]

https://www.dupont.com/content/dam/dupont/amer/us/en/performance-building-solutions/public/documents/en/styrofoam-brand-highload-40-60-and-100-pis-43-d100994-enNA.pdf

At the bottom it says for static loads 3:1

Nys dot says 1% but I think that’s a but extreme you’re better off cutting it out at that.

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-repository/GEM-24b.pdf

This may or not be of any help: https://www.wbdg.org/FFC/DOD/UFC/ufc_3_220_20_2025.pdf

Thanks for the references. Since the foam is relatively uniform, would it be accurate to say that the subgrade modulus is of little effect and it's more of just a bearing check?

 

[canwesteng]

Not sure that it being uniform is the reason it is of little importance, but it is pretty thin (probably 50 or 100 thick) relative to the soil, so most deflection should still come from the soil, even if the soil is stiffer.