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RE: Using Geofoam under parking lots

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Title: Using Geofoam under parking lots
We often use close-celled polystyrene (pink or blue board) under buildings and roadways. The compressive strength range up to 60 psi (8640 psf).
Note that 10 psi (1440 psf) is also a good load capacity when buried using the shear value of the road gravel to spread the load pressure.
What is really important is the materials ability to resist water absorption that degrades the strength and thermal resistance values.
We also place a petroleum resistance liner above the insulation if spills may occur.
-----Original Message-----
From: Mark [mailto:imagineer66(--nospam--at)]
Sent: Wednesday, August 17, 2005 11:09 AM
To: seaint(--nospam--at)
Subject: Using Geofoam under parking lots

Project: Snow Melting under parking lot and alleyway.  The kicker is that occasionally a 15-ton crane to remove rooftop equipment, etc. sets up in the alleyway.

The manufacturers of the hydronic snow melt system require insulation under their tubing because the water table is within 8 feet.  After some research, I've found that GeoFoam is used under highways, bridges, and abutments.  This sounds like it might be the stuff to use.  I've gone to several websites (,,, and a couple of manufacturer's sites).  Alas, I still don't have a good handle on this. 

Has anyone used this under roadways?  Is 10psi flexural strength really strong enough to support heavy vehicles?

Thanks in advance,
Mark Jones