The degree of load capacity that a given (building) material can tolerate permanently, without any change in size or quality.
In the case of thermal insulation materials, the long-term load capacity is characterized by a compressive strength at 2 % material compression over the long term. The long-term load capacity of the RAVATHERM XPS is described by the CC performance feature. This allows for a maximum total compression of 2% over 50 years at the specified maximum compressive strength.
Floor structures and slab foundations shall be calculated with this value in the case of other permanent loads!
Important! Durable load capacity (CC) is not the same as the compressive strength value for the 2% compression of the insulation material, as specified by some manufacturers.
Interesting fact: thermal insulation products are usually classified using the compressive capacity values measured at 10% compression, or sometimes (for some XPS products) their compressive strength. However, the strength values for 10% compression are not design values, because thermal insulation materials usually suffer permanent deformation over a certain compression under the influence of a certain load. They suffer further deformation following so-called initial compression under long-term load.
E.g. The EPS, which is similar to XPS – according to product standard MSZ EN 13163, expanded polystyrene foam – thermal insulation materials no longer behave elastically over 2-3 % compression, the cells suffer permanent deformation.