EPS behaves as a linear elastic material up to a strain of about 1% as shown in the figure above that depict the stress-strain response of EPS. As a result, the design recommendation for EPS geofoam is to limit loading to the compressive resistance at 1% strain. The stress at a compressive strain of 1% is called the elastic limit stress and is measured in a standard rapid-loading compression test. Except for special compressible applications, higher compressive strain, e.g., 5 or 10%, is not used to estimate the EPS strength because these strains are past the yield strength of the EPS and this may lead to undesirable permanent strains.