Prüfung der Druckfestigkeit von Außenputz auf Mauerwerk

Testing the compressive strength of external rendering on masonry.

The important properties of external renderings have to be adapted to the respective rendering base, especially in case of masonry made of high thermal insolating light clay units, to avoid unintentional crack formation in the rendering extending into the rendering base. A criterion for the adaptation between rendering and base is the compressive strength of the rendering, which should not exceed 5 N/mm². The compressive strength of the rendering can be tested according to DIN 18555-9, test method II or III. Preferably, it should be determined with test method III by use of small plates of the rendering taken from drilled masonry samples. A relation of these compressive strength values to values tested on prisms (standard test method according to DIN EN 1015-11) does exist. Thus, the upper limit value of the compressive strength tested on prisms can approximately be determined, with which it can be assumed that the compressive strength of the rendering on the masonry wall does not exceed the recommended value of 5 N/mm².