Wet area specification
Microcement In Bathrooms And Wet Rooms
A microcement bathroom lives or dies on what happens below the finish. Get the tanking, falls and junction details right and the room is genuinely seamless. Get them wrong and the surface becomes the visible symptom of a hidden problem.
The waterproofing is not the microcement
This is the single most misunderstood point in wet room specification. Microcement sealers repel water at the surface, but the waterproof layer is a separate tanking membrane installed underneath the finish. In a shower enclosure and across any wet zone, that membrane and its bonded corner tapes are what keep water out of the structure.
When a wet room fails it is almost never the coating that let go. It is a membrane that stopped short of the splash zone, a pipe penetration that was never collared, or a movement junction between two different substrates that was bridged rigidly. Ask any contractor to show you the tanking system by name and where its coverage starts and stops.
- Tanking
- Bonded membrane with taped internal corners, below the finish
- Shower falls
- Formed in the substrate or a proprietary former, not in the coating
- Finish depth
- Around 2 to 3 mm over the membrane
- Sealer
- Multi-coat schedule rated for continuous wet exposure
Build-up sequence in a typical wet room
- 1Strip and assess
Existing tiles, boards or vinyl come off or are tested for bond. The condition of what is behind determines everything that follows.
- 2Board and form
Tile backer boards, a shower former with the correct fall to the drain, and any bench or niche geometry are set out and fixed.
- 3Tank
Membrane applied across the wet zone, with tapes into every internal corner, around the drain flange and at pipe penetrations.
- 4Prime and mesh
A bonding primer goes down, followed by base coats with reinforcing mesh across board joints and change-of-substrate lines.
- 5Finish and seal
Fine finish coats are trowelled, cut back, then a multi-coat sealer schedule is applied with the correct interval between coats.
Details that decide the outcome
Drains, thresholds and glass fixings are where a seamless room stops being seamless. A linear drain set flush with the finished level is far more forgiving than a point drain in a small enclosure, because it needs a fall in one direction rather than four. Glass screens that are drilled through the finish after sealing need the fixing holes sealing properly, and that step is regularly missed.
Sanitaryware sequencing matters too. Wall-hung units, concealed frames and pipe runs need to be in position before the finish goes on, because any drilling afterwards breaks the sealer film. On a design-led scheme the coordination between the plumber, the glazier and the applicator is worth more attention than the colour choice.
- Linear drain preferred over a point drain in small enclosures
- Concealed cistern frames fixed and tested before the finish is applied
- Fixing penetrations sealed individually, not just wiped over
- Junctions between board and masonry meshed rather than butted
Living with the finished room
A sealed microcement bathroom cleans with warm water and a pH-neutral product. What shortens its life is the household chemistry cupboard: limescale removers, bleach-based sprays and abrasive creams all attack the sealer film rather than the cement beneath, and once the film dulls, water starts sitting on the surface instead of beading off.
In hard water areas, drying the shower walls after use makes a visible difference to how long the surface holds its sheen. Sealers are consumable and can be refreshed. That is a maintenance item, not a defect, and it is worth building into a client handover pack on any development.
Wet room questions worth asking
Before you sign off a wet room spec
Ask for the tanking system, the drain type, the fall arrangement and the sealer schedule in writing. If those four things are clear, the finish will look after itself. Send us your bathroom drawings and we will mark up where the risk sits.