Where microcement works and where the trouble starts
Microcement works on walls, in a living room, in a bathroom with good waterproofing and on a flat, stable floor. Trouble starts where the substrate moves: over old tile with hollow spots, on a poorly cured screed, at junctions of different materials and on heavily used steps or shower trays without waterproofing.
It is a thin coating, 2–3 mm including primer and sealer. It does not hide defects, it repeats them: a crack in the substrate shows on the surface within weeks. So the result is decided mostly by preparation, with skill at application coming second. Good microcement looks expensive; bad microcement looks like grey filler, and the difference shows within a year.
Why microcement cracks and whether it can be avoided
There are four causes: substrate movement, tile joints under the coating, a layer that is too thick and poor drying. Cracks can almost always be avoided if the project covers three things. First, the screed must cure and dry to the moisture level stated by the system manufacturer, not by feel. Second, fibreglass mesh runs across the whole area and bridges the joints of the substrate. Third, on large areas and over the building's structural joints, microcement joints are cut and carried through.
Fine hairline cracks in a corner or where wall meets floor can appear even with good work. That is normal shrinkage and is closed at handover. If a crack follows the line of an old tile joint, the substrate was not reinforced.
Can microcement go over old tile
Yes, with conditions. The tile must be well bonded with no hollow spots (checked by tapping), joints levelled with filler, the surface degreased and primed with a bonding primer, and mesh goes on top. Then it works on a bathroom wall. On a floor the relief of the joints often shows through under raking light, and that is your call: accept a faint grid or remove the tile.
The second risk is height: tile, adhesive and microcement add up to about 1 cm, which affects doors, thresholds and the levels of neighbouring rooms. In Eixample flats with uneven floor slabs, that centimetre often decides whether all the tile comes out. For a shower without demolition, tile counts as a substrate only if complete waterproofing goes over it.
Microcement in a shower: is waterproofing needed underneath?
Yes, always. Microcement is cement-based with polymers and is not watertight on its own: protection comes from the sealer on top, which is thin and wears. Waterproofing goes underneath: a liquid membrane with tape in corners and around the drain, or a sheet. A 1–2 % slope runs to the drain, linear or point, recessed so the layers finish flush.
Bad news for the undecided: a microcement shower is for people who want a seamless floor and wall, and it demands the build-up to be exact: membrane, mesh, two or three coats, sealer. Built like that, the shower lasts for years. Without a membrane, water passes under the sealer, the cement base soaks and the coating lifts in blisters.
Microcement and underfloor heating: what to watch
Underfloor heating is compatible with microcement, but the order is strict. First the screed cures, then heating cycles run according to the heating manufacturer's schedule, it cools to room temperature, and only then is the coating applied. Applying it onto a warm substrate causes microcracks and poor adhesion.
After application the heating is restarted gradually, a few degrees per day following the manufacturer's schedule, keeping surface temperature moderate. Sudden jumps open joints. If you want the floor to stay beautiful, do not run the heating at full power in the first winter. On large areas, plan movement joints at the boundaries of the heating circuits: the microcement joint layout follows the circuit layout, so joints sit on joints.
How often to reseal a microcement floor and what to demand from the applicator
Floor sealer wears faster than on a wall: in a normal living area it lasts years, but at constant friction points (entrance, kitchen) it is renewed sooner, usually every two to four years depending on condition. In a shower you judge by eye: dull patches and loss of water repellency say it is time.
From the applicator, demand four things. Work with one system from one manufacturer, from primer to sealer. A trial sample of at least 1 m2 in your combination of base and colour. Coats, consumption and intervals in writing. And a care protocol: what to clean with and what not to. Acids, chlorine and abrasives damage the sealer; a neutral cleaner and a soft mop preserve it.
How BCN YARD can help with microcement
We inspect the substrate before choosing the finish: if porcelain or tile is the better choice, we say so before application, not after. If microcement fits, we build the layers for your shower or floor and agree the sample. We run the project in Russian and Spanish, under a contract with staged payments. Send photos of the room and we will reply within an hour.
Frequently asked questions
How long does microcement last in a bathroom?
With proper waterproofing and sealer renewal, the base lasts decades, while the protective layer is renewed every few years. Lifespan depends on the build, not the material: membrane, reinforcement and sealer quality. Complaints of cracking after a year almost always trace back to poor substrate preparation.
Is microcement slippery?
It depends on the sealer and finish. For a shower and a wet-zone floor, choose a matte, fine-grain finish with an anti-slip additive in the sealer, and keep smooth gloss for walls. Ask the applicator for a sample and test it with a wet bare foot before approving.
Can a scratch in microcement be repaired?
Light scratches are removed by sanding and local sealer; deep ones need recoating and colour matching. A fully invisible patch is rare, which is why the whole plane is repaired from corner to corner. Keep a leftover of the mix from the same batch: years later a different batch will not match in colour.