What is Geofoam?

Geofoam is not the commodity white foam typically found in your local hardware store, it is a stronger engineered foam for an engineered solution. Geofoam is a lightweight, rigid foam plastic (EPS – Expanded Polystyrene) that has been used around the world as a fill for more than 30 years. It is approximately 100 times lighter than most soil. This extreme difference in unit weight compared to other materials makes EPS geofoam an attractive fill material in both transportation and non-transportation applications. EPS geofoam also reduces lateral stress encountered with traditional materials, especially in embankment situations.

Common Geofoam Applications:

  • Slope Stabilization
  • Bridge Abutments
  • Embankments
  • Theater “Stadium” Seating
  • Retaining Structures
  • Utility Protection
  • Pavement Insulation
  • Shallow Foundations

Not all EPS meets geofoam requirements. Take no risks!


Many suppliers of foamed plastics in good faith report that their material is “UL Classified”. While most construction plastics can be found in the UL online certifications directory for Surface Burning Characteristics (BRYX), most are NOT classified geotechnical report nz for Physical Properties.

When listed in the certifications directory for Physical Properties, this is typically limited to compliance with ASTM C578-08b. HOWEVER, the compressive strength testing for C578-08b is at 10% deformation.

By the time the foam has reached 10% deformation, it is permanently dented — the road, building, or abutment is sinking or leaning at this point! The more important properties are verified against ASTM D6817-07, in the 1-2% elastic region of the foam deformation (takes the stress & bounces back).

In slope stabilization or other geofoam applications, it is imperative that the physical properties of the EPS foam be assured to prevent creep and other long-term failure issues.

Insist that your supplier verify independent, ongoing 3rd party verification of physical properties vs ASTM D6817-07.

What does it cost?

The value chain for EPS Geofoam is petrochemical-based: that means its cost is correlated to the cost of oil. Below is an example of approximate cost of Geofoam compared to cost of oil.

Selecting the Right Product Grade

Selecting the correct material for your project is important. If underspecified, the project could fail. If overspecified, money is wasted on extra strength that goes unused. We urge our clients to contract with a civil engineer to help specify the correct grade of product. In general, the engineer will use the dead load of ballast and topping materials, the live load during use (such as traffic), and a safety factor to assure the correct maximum loading is calculated. From this, the load can be converted to pounds per square inch (psi). Then it is simply a matter of selecting the grade from the table that exceeds this psi value at 1% compressive deformation.


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