Microcement

The microcement item covers the whole surface finishing system on a prepared substrate. It includes cleaning and priming, embedding a glass fibre mesh on substrates at risk of cracking, two or three coats of base and finishing microcement with sanding between coats and, finally, a protective sealer in two or more coats. Treating corners, edges and transitions to other materials is part of the job as well.

The item normally does not include levelling large unevenness, a new screed, waterproofing of the shower, removing and refitting sanitaryware or any demolition. If the substrate is not flat and sound, that is dealt with as a separate job before the microcement is applied.

Where it works well

• bathroom renovations where sound old tiles should stay in place,
• floors in living rooms, kitchens and hallways that should look continuous, without thresholds,
• showers and walls around a bath, as long as the waterproofing is done properly,
• kitchen splashbacks, worktops, stairs and furniture made from rigid boards,
• shops, cafes and offices where an industrial look is wanted.

Where it is more of a risk

• substrates that move, such as old parquet, timber boards without stabilisation or springy plasterboard floors,
• fresh screeds and plasters that have not dried yet,
• substrates with rising damp, for example a basement without a damp-proof course,
• surfaces with active cracks and movement joints that someone wants to cover without a break,
• outdoor areas, unless the manufacturer offers a system intended for exterior use.

Microcement is not a substitute for repairing the substrate. Manufacturers agree that whatever moves underneath will sooner or later show on the surface.

The substrate must be sound, dry, clean and stable. Most often it is a cement or anhydrite screed, plaster, concrete, plasterboard on walls or old ceramic tiles. With tiles, the first step is to check that none of them are hollow. Loose tiles are replaced or re-bonded, the surface is degreased and the grout joints are filled so that they do not show through the thin layer.

Absorbent substrates such as plaster and screed receive a primer that evens out their absorbency. Non-absorbent ones, such as glazed tiles, receive a bonding primer with sand so the microcement has something to grip. On substrates where cracks are likely, a glass fibre mesh is embedded in the first coat. The manufacturer of the system specifies the right primer, and it is not a good idea to combine products from different brands.

New screeds must be allowed to dry properly. The exact moisture limit is set by the manufacturer, and in practice it is measured with the carbide method or a moisture meter. With underfloor heating, the screed must be heated up according to a heating protocol before the work starts.

1. Check the flatness, strength and moisture of the substrate and tap it to find hollow spots.
2. Repair unevenness and cracks, and on tiles fill the joints and sand the glaze.
3. Vacuum the dust and degrease and clean the substrate as the manufacturer instructs.
4. Apply the primer or bonding primer suitable for the substrate and let it dry.
5. On substrates at risk, embed a glass fibre mesh in the first coat with overlaps.
6. Apply the first base coat of microcement thinly with a steel trowel.
7. Once dry, sand the coat and vacuum the dust.
8. Apply another base coat and sand again.
9. Apply one or two finishing coats of fine microcement, which define the final look.
10. Let the finishing coat dry, sand it lightly and remove all dust thoroughly.
11. Apply the protective sealer with a roller in at least two coats according to the technical data sheet.
12. Protect the surface from water and loads until it has fully cured.

To give you an idea of the timings: the Danish manufacturer Urban Hald states in its instructions that microcement coats are up to 1 mm thick, need 2 to 4 hours to dry before sanding, that the last coat needs at least 12 hours before sealing and that the second coat of sealer follows after 8 hours. According to the same instructions, the surface can be walked on in socks after 24 hours, but it is only watertight and fully cured after 7 days. Other brands have similar but not identical times, so the technical data sheet of the system used is what counts.

One-component and two-component microcement

One-component systems are simply mixed with water. They are easier to prepare and suit smaller areas. Two-component systems are mixed with a polymer resin, which increases flexibility and adhesion. For floors that take heavier loads and in bathrooms, two-component systems are chosen more often.

Coarse and fine microcement

Base coats are made from a coarser material that provides strength. Finishing coats are fine and define the texture. A fine surface looks smooth and matt, a coarser one looks more like stone and is less slippery. For bathroom floors, a slightly coarser finishing coat or a sealer with an anti-slip additive is often chosen for this reason.

Sealers and protection

The sealer is what protects microcement from water, grease and stains. Two-component polyurethane sealers in matt, satin or gloss finishes are used most often. The sealer must come from the same manufacturer as the microcement. A different sealer can leave blotches on the surface or start to peel.

Colour

Microcement is coloured with pigments directly when it is mixed. The shade is therefore mixed for the whole area at once or to an exact recipe. When topping up, it is hard to hit exactly the same shade, which is why small repairs on a large surface usually cannot be made invisible.

Sealed microcement resists water, but on its own it is not waterproofing. In a shower and around a bath, a waterproofing layer is therefore applied first, with sealing tapes in the corners and collars around the drain and the taps. With a level-access shower, the fall to the drain must already be formed in the substrate, the microcement simply follows it.

Microcement can be applied over underfloor heating. According to manufacturers, the heating is switched off several days before application and switched on again only once the sealer has cured. Urban Hald specifies switching it off at least 72 hours before work starts and switching it on no earlier than 24 hours after the last coat of sealer. The temperature should then be raised gradually. Sudden heating causes stress and hairline cracks.

Application takes place at room and substrate temperatures of roughly 10 to 25 °C. In the cold it dries slowly and may not cure properly, while in heat and draughts it dries too quickly and is hard to trowel.

• poorly prepared substrate: hollow tiles, dust or grease cause peeling and cracking,
• covering a movement joint: movement in the substrate is transferred to the surface and a crack appears exactly above the joint,
• a substrate that moves: on parquet or a springy floor, even the mesh cracks,
• too thick a coat at once: the material shrinks and forms a network of hairline cracks,
• skipped sanding: the next coat bonds less well and the surface is uneven,
• badly mixed pigment: darker streaks and blotches appear on the surface,
• sealer from another manufacturer: colour change, milky patches or peeling,
• no waterproofing in the shower: water gets through micro-cracks to the substrate and the tiles underneath,
• exposure to water too early: the sealer has not cured yet and white marks remain on the surface.

In practice, owners sometimes expect a surface as uniform as a lacquered board. Microcement is handwork, and trowel marks and subtle differences in shade are part of it. It is therefore worth looking at a sample or a reference job by the same crew before work starts and agreeing which look is still acceptable.

When deciding, microcement is most often compared with large-format tiles and with poured epoxy or polyurethane floors. Each solution follows a different logic.

• microcement: a thin layer without joints that can also be applied to walls, furniture and stairs. The look is handmade and every surface is a little different. It needs regular care of the sealer,
• large-format tiles: very durable and almost maintenance-free, with few joints, although they never disappear completely. In a renovation, the old surface is usually removed and the substrate levelled,
• poured floor: a self-levelling layer intended mainly for floors and resistant to wear, but unsuitable for walls and showers, and it looks more technical.

Microcement wins where a continuous surface across floor and walls matters and where removing old tiles would mean a lot of dust and time. Tiles win where the least possible maintenance and maximum durability are expected, for example in an entrance hall or a utility room.

The small area between the worktop and the wall cabinets is a good place for a first attempt. A mistake here can be put right without great cost, and you learn the technique just as you would on a floor.

1. Buy a complete system from one manufacturer: primer, base and finishing microcement, pigment, sealer and trowel.
2. Switch off the circuit breaker, remove sockets and switches, and mask the worktop, cabinets and surroundings with tape and sheeting.
3. Sand and degrease the old tiles, fill the joints and apply the bonding primer.
4. Mix only as much material as you can use within its pot life, following the instructions.
5. Apply a thin first coat, let it dry and sand it.
6. Apply the second and the finishing coat, holding the trowel at a shallow angle and working in crossing strokes.
7. Once dry, sand with fine paper, vacuum and wipe with a damp cloth.
8. Apply the sealer with a roller in two thin coats and keep to the waiting time between them.
9. Remove the tape before the sealer has fully cured so the edge does not tear.
10. Let the splashback cure fully before exposing it to water and grease.

Microcement is an interior surface finish, but check with your local authority whether your particular project needs any approval. In a block of flats, follow the house rules, especially the hours for noisy work such as sanding, and remember when working on a shower or drain that a leak could damage the flat below.

Look at the surface in raking light, for example with a torch placed on the floor. This makes unevenness, sharp trowel edges and spots without sealer stand out. Tap across the surface, the sound should be the same everywhere. Run a finger along edges and corners, they should be neither sharp nor chipped.

In the shower, once everything has fully cured, run the water and watch whether it flows to the drain and does not stand anywhere. For a bathroom, ask for information on the waterproofing used and for photos taken before the microcement was applied.

Handover checklist

• the surface is continuous, with no cracks or peeling spots,
• the shade is the same across the whole area, without noticeable streaks,
• the sealer has been applied everywhere, including edges, corners and around the drain,
• movement joints have been kept and filled with a flexible sealant,
• transitions to sanitaryware, thresholds and other materials are clean and sealed,
• water in the shower runs to the drain,
• the contractor has handed over the name of the system and the sealer and care instructions,
• it has been agreed when the surface can take full loads.

For everyday cleaning, water with a pH-neutral cleaner is enough. Aggressive cleaners, chlorine, abrasive pastes and steam cleaners damage the sealer. Felt pads go under furniture legs. On a floor with heavy foot traffic the sealer is renewed after some years, and manufacturers recommend applying a maintenance coat regularly so the surface stays attractive and durable.

In the NUMIQ price list, microcement is calculated as labour per m², including minor consumables. The microcement system itself and the sealer are listed separately as material. The base labour price is around 80 € per m². Prices vary by region and city, and are usually higher in large cities.

The result depends mainly on the condition of the substrate and the size of the area. A small bathroom with many corners, niches and penetrations takes longer per square metre than a large flat floor. Walls and ceilings are slower than floors. It also matters whether a mesh is needed, whether tiles need a bonding primer, how many finishing coats are applied and which sealer is used. Substrate repair, levelling and waterproofing are calculated as separate jobs.

If you are considering classic tiles, read Tiling Services. A similar decorative wall finish is described in Venetian Plaster - Polished Stucco. Waterproofing under a shower is covered in Waterproofing Coating (Around Bathtub, Around Washbasin, Under Shower Tray).