Structural tests have been completed on several papercrete formulas and Fuller claims the compressive strength of papercrete to be in the 140-160 psi range (0.96 - 1.1 MPa), while others like Kelly Hart claim 260 psi (1.7 MPa). For comparison, the compressive strength of concrete ranges from 15 MPa to over 70 MPa (2200 - 10000 psi) depending on the application. A more useful measure of papercrete's properties is its stiffness - i.e. the extent to which it compresses under load. Its stiffness is many times less than that of concrete, but sufficient for the support of roof loads in some low-height buildings.