Is Microcement Waterproof? The Honest Answer

Short answer: yes. The longer answer is the useful one, because which layer is doing the waterproofing is the whole difference between microcement and the decorative finishes it gets confused with.

The microcement is waterproof, not the sealer

This is the part people get backwards. Microcement is waterproof in itself — the body of the material, not the coating on top of it. That is why it works in showers, bathrooms and splashbacks.

Compare that with a decorative plaster or a limewash. Those are porous. The sealer or wax over them is the only thing standing between water and the wall, so the day that coating wears thin in the corner of a shower, you have a problem in the substrate and no way of knowing until it shows.

With microcement, if the sealer wears you have a finish that stains more easily. You do not have water in the wall.

So what is the sealer actually for?

It protects the finish — from staining, from cleaning products, from the daily abrasion of feet and pans and shower gel. It is what makes the surface washable.

That does not make it optional. Two coats of sealer go on every job, no exceptions. Skipping it or rushing it is the single most common way a good application ends up looking bad six months later. But understand what you are protecting: the look, not the structure.

What still has to be right

Here is the sentence worth reading twice: a waterproof surface over a discontinuous detail still fails.

Wet rooms live or die on the waterproofing behind the finish. It has to be continuous into every junction — the drain, the curb, the niche, the bench, the corner where the wall meets the floor, every pipe penetration. Microcement being waterproof does not rescue a gap behind it. It never has, for any finish.

This is exactly the same discipline a tiled wet room needs. It is not a microcement problem. It is just the job.

Which system you need

Core is primer, microcement, sealer. It covers interior walls, bare concrete floors and indoor fireplaces.

Reinforced adds fiberglass mesh bedded into a structural build coat. You need it for anything wet, anything outdoors, and any floor that is not bare concrete. The mesh is what stops movement underneath reaching your finish.

For anything wet the answer is always Reinforced. Not because of water — the microcement handles water — but because of movement. A bathroom floor flexes, a shower bench is a change of plane, and the mesh and build coat are what stop that movement arriving at the surface as a crack. A crack is how water finds a way past a waterproof material.

There is no version of a bathroom where Core is the right call, including the dry corner by the door. You do not want a system change running through a seamless floor.

What about mould?

Most bathroom mould does not live on tile. It lives in grout and in silicone — porous, textured joints that hold moisture and soap residue. Microcement has no grout lines and no joints, so it takes away the place mould normally colonises.

That is a real advantage and it is why a lot of people end up here. It is not the same as saying nothing can ever grow on it: a surface that stays wet and never dries will grow something regardless of what it is made of. Ventilation still matters.

The three ways people get this wrong

Using Core in a wet area. No mesh, no build coat, movement reaches the surface. This is the big one.

Treating the sealer as the waterproofing. It is not, and thinking it is leads to people economising on the wrong thing.

Assuming a waterproof finish fixes a bad detail. The drain, the curb and the penetrations are where bathrooms fail, in every material.

Common questions

Can it go on a shower floor? Yes, with the Reinforced system and the waterproofing underneath done properly. Slip resistance is a finish and sealer decision — ask us about your specific job rather than assuming.

Does it need a tray or a threshold? No. That is the point of a wet room in microcement: the floor and the walls are one continuous surface.

Can it go under water, in a pool? Permanently submerged surfaces are a different specification. Email us rather than assuming this page covers it.

What if it chips in a shower? It is repairable in place, which is more than you can say for a cracked tile in the middle of a run.

Microvella ships late 2026. Join the waitlist and we will email you the day it is ready to order.

Related: Microcement for bathroom remodelers · Microcement shower installation · Shop the full system