Microcement is fully suitable for wet rooms when correctly detailed. We've installed in over 200 shower zones, steam rooms and full wet-rooms with zero warranty claims relating to water ingress. This is how we do it.
The substrate
We don't waterproof with microcement — we waterproof under it. The base of every wet-room install is a two-component cementitious membrane (Mapelastic Aquadefense or equivalent), reinforced at corners and waste pipes with bonded mesh tape.
The fall
1.5–2% fall to the drain across the shower zone. We don't accept lipped trays or framed enclosures that interrupt the fall — the visual point of microcement is the continuous floor, so the fall has to be in the substrate, not bodged with silicone at the threshold.
The microcement build
Primer + mesh + two build coats + one finish coat, identical to a dry-area install. The mesh runs around shower corners and 200 mm up the wall on all sides to bridge any wall/floor movement.
The sealer
Two-component aliphatic polyurethane sealer (4 coats over 24 hours). This is the layer that does the water work. It's specified for swimming-pool surrounds, so a shower floor is well inside its design envelope.
The first 24 hours
The room is unusable for 24 hours after sealer application. Day two, light splash is fine. Day five, full use.