Limits of water absorption of façades

When does a facade absorb too mech water?

It’s very simple. When there is damage because of leaking rain water, there is always something wrong and the limit is met. The quantity of absorbed water which leads to damage is always too much.

An outer cavity wall is destined to take in water and give it back. At the bottom the water resistant foils or other means are in place to guide this rain water outside, without causing resulting damage inside. If the used façade stone, laying mortar and joint mortar are sufficiently frost proof with the right composition, there is no problem. However when one of these products is not sufficiently frost proof, or degrades, plasters, strongly discolours or gets instable there is (possibly) a problem.

The Karsten tube (picture) is used to check the durability of the hydrofuge in comparison with a non-treated wall. Also see ASTM E-514 test, RILEM 25 PEM (Reunion Internationale des Laboratoires D’Essais et de Recherches sur les Materiaux et les Constructions), The American norm SAE J1960 and the German norm DIN 52615, Belgian Institute for Normalisation NBN EN 196-1, NBN EN 1936, ICCROM – International Centre for the Study of the Preservation and Restoration of Cultural Proprety, WTCB TV 224 2002.

When there is damage, determine the cause or source an check it with the “insurance technical equivalence theory”. If the one cause had not been there, would there be damage? The liable party of that one cause is completely liable for the caused resulting damage, even if this is indirectly caused (see equivalence theory).