Microcement bathrooms in Mallorca

The bathroom is where microcement is most requested, and also where we see the most failures in other people's work: dark stains at the base of the shower, tile joints showing through, sealer lifting around the drain. None of them comes from the material; they come from treating it as a thick paint rather than as a system. Here we explain how a microcement bathroom is done over tiles so that this does not happen.

Microcement over bathroom tiles

The existing tiles are a good substrate if they are firm. We tap them one by one; those that sound hollow are removed and the gap filled. The joints are levelled with a levelling paste until the surface is continuous, and the glaze is sanded to open it up. Then comes a bonding primer for non absorbent substrates. With the substrate prepared like this, the microcement does not know there are tiles underneath.

Floor standing sanitaryware, the toilet and the bidet, is taken off so the microcement can go underneath; a wall hung basin and the taps are protected and the microcement is finished against them. The shower screen is removed if it is fixed in place and refitted on the sealed microcement with neutral cure silicone, never acid cure, because acetic acid attacks the polyurethane.

The waterproofing goes underneath, not on top

This is the point that separates a well made bathroom from one that gives trouble. Sealed microcement repels water, but it is not a membrane: the mortar is cementitious and the polyurethane is a few tenths of a millimetre thick. In a shower, where water falls on the same spot for minutes every day, a micropore or a scuff is enough for moisture to reach the mortar and leave the dark stain that does not go away.

That is why in the shower area, floor and walls up to at least two metres, we apply a flexible cementitious waterproofing mortar before the microcement, in two coats, with elastic tape at the corners, at the junction between floor and wall and around the drain. The primer and the microcement go on top of that layer. If water ever gets through the sealer, it stops at the waterproofing and does not reach the slab or the neighbour below. In the rest of the bathroom, outside the shower, this layer is not needed.

The shower tray and the drain

A microcement shower tray is built in place, with a 2 percent fall towards the drain. If the bathroom already has a tiled built-in tray, it is kept; if it has a ceramic or resin tray, the usual approach is to remove it and form the new one in mortar. The drain is the most delicate point: the microcement and the waterproofing have to finish against the drain flange, which must be a model with a flange made for membranes. An old drain without a flange is the most common cause of sealer lifting around the drain.

A linear drain, against the wall or across the front of the shower, is the one that works best with microcement: the fall runs in a single direction, the floor stays flatter and there is only one junction to protect. On the floor of the shower the sealer carries anti-slip aggregate; wet and soapy, smooth microcement is slippery.

Walls: how high to go

Bathroom walls can take microcement up to the ceiling or to a set height, finished with a profile or with a clean line and paint above. In the shower we recommend going up to the ceiling or at least to two metres, because of splashes and steam. Outside the shower, the height is an aesthetic choice. Corners can be left sharp or rounded; rounded ones are easier to clean and are the usual choice in built-in trays.

Bathroom floor and junctions

The bathroom floor outside the shower is treated like any microcement floor: joint levelling, mesh, four coats and sealing. The junctions with the base of the toilet, the basin pedestal and the door frame are finished with neutral cure silicone in the colour of the microcement once it has been sealed. The door rarely needs trimming: the system adds about 3 mm.

Colours for a microcement bathroom

Mallorca's hard water leaves a white film of limescale that shows clearly on dark tones, especially inside the shower. Off-white, sand, pearl grey or taupe make a small bathroom feel larger and hide limescale and soap; anthracite or cement grey look better on the basin wall or a built-in unit than in the shower tray. In the shower tray, a matt or satin finish with aggregate, never gloss. The families and finishes are covered in microcement colours and finishes.

Timescale for a microcement bathroom

A complete bathroom, floor and walls, usually takes five to eight calendar days: one or two for preparation and waterproofing, three or four for the microcement with its drying times, one for sealing, and then the curing days. You can walk in with clean footwear 48 hours after sealing. The first shower comes after 7 days, when the polyurethane has reached its hardness.

Maintenance of a microcement bathroom

pH neutral soap and water; no limescale remover, bleach or ammonia. Mallorca's water is hard and leaves a white film on the sealer: remove it with a damp cloth after showering, or with a squeegee on the screen and walls, and not with acid products. Ventilating after a shower prevents mould in the corners, which cleans off microcement but stains it if left for weeks. And check the shower tray every two or three years: when water stops running off and darkens the surface, it is time to renew the sealer, a one day job.