Damp rooms
A bathroom is not a shower: its walls get steam, condensation and the odd splash, but no running water. That is good news, because many mineral renders thrive there — lime in particular takes moisture from the air and gives it back, which avoids the condensation that streams down a sealed wall.
The test
Included: renders and stuccos whose water verdict is at least “steam only”. Clay and gypsum renders are left out: they break down when damp lasts.
RenderCement + resin · 2–3 mm
A mineral render as one continuous surface with no joint anywhere — the only finish here that runs from floor to wall in a single material.
Photo Alex van Olst · CC BY-SA 4.0 · Wikimedia Commons
StuccoHydraulic lime (NHL) · 3–6 mm
The one lime finish that takes running water — and it is the soap, not the lime, that makes it waterproof. The floor of hammams for centuries, walls and floors alike.
Photo Eigenheym · CC BY-SA 4.0 · Wikimedia Commons
StuccoAir lime (CL) · 0.5–1 mm
The same gesture taken to a polish: a very fine marble flour, worked with the iron until the gloss of marble comes up.
Photo SchiDD · CC BY-SA 4.0 · Wikimedia Commons
RenderHydraulic lime (NHL) · 1–3 mm
A material rather than a colour: one to three millimetres trowelled on, giving the wall a relief and a depth no paint imitates.
Photo Jules Verne Times Two · CC BY-SA 4.0 · Wikimedia Commons
StuccoAir lime (CL) · 1–2 mm
The everyday Venetian stucco: two coats compressed with the blade, closing the surface without taking it to a shine.
Photo Kubko666 · CC BY-SA 3.0 · Wikimedia Commons
Among paints, these pass the same test: Badigeon de chaux, Peinture à la chaux, Peinture au silicate, Peinture acrylique.