Is Microcement Waterproof?

How Sealing Creates Waterproofing

Microcement in its base state is a cementitious material with inherent porosity. Without a sealing layer, it behaves like any cement-based product — absorbing moisture, staining and deteriorating when exposed to water. The waterproofing in a microcement installation comes entirely from the sealant layer applied as the final stage of the installation process.

Polyurethane sealant forms a continuous, flexible film over the microcement surface. When applied in the correct number of coats and allowed to cure fully, this film is completely impermeable to water. The flexibility of PU sealant is also important — it accommodates the minor thermal movement that occurs in any building without cracking, maintaining the waterproof barrier over time.

Epoxy sealant provides a harder, more chemically resistant waterproof film suitable for the most demanding wet environments — commercial spa pools, wet treatment rooms and heavy-use shower areas. Epoxy is less flexible than PU but provides superior abrasion and chemical resistance.

Wet Rooms and Showers

For shower areas and wet rooms, a minimum of three coats of sealant is required. Critically, the wall-floor junction — the line where wall meets floor — must be fully sealed with no gaps. This junction is the most common point of water ingress in poorly installed microcement bathrooms. Professional application includes careful attention to this detail.

What Happens Without Sealant

Unsealed microcement exposed to water will absorb the moisture and develop dark, blotchy staining patterns. These stains are very difficult to remove and in severe cases require full resanding and resealing. This is why sealant application is never optional — it is a critical, load-bearing element of the microcement system.