22 June 2026

Facade impregnation: when is it worthwhile (and when not)?

Impregnation keeps rain out and grime away — but only on the right facade, at the right moment. The checklist.

During impregnation an invisible, water-repellent agent soaks into the stone. Rain now beads off the facade instead of soaking in: the wall stays drier, green algae gets less grip and the facade stays clean for years longer after a cleaning visit. The agent does not seal the facade — water vapour from inside can still escape.

It is worthwhile in three situations. After a cleaning visit: the facade is clean and dry, exactly the surface the agent bonds to best. On a facade that greens up quickly, for instance facing north or under trees: the impregnation layer removes the moisture algae grow on. And with penetrating damp: if rain strikes through to the inside wall, water-repellent treatment is often the least invasive solution.

When not? On a painted or coated facade — it simply won't absorb the agent. On a facade with failing pointing: repair the joints first, otherwise you are impregnating a wall that keeps taking in water along the joints. And not when the moisture comes from inside (rising damp, condensation): an exterior treatment won't solve that, and you need a proper diagnosis first.

The costs are straightforward: € 8 to € 15 per m², and the effect lasts 5 to 10 years on average. Combined with a cleaning visit you pay for call-out and scaffolding once — check the numbers in the price index and request quotes with and without impregnation, so you see the price difference exactly.