Walk-in showers: what the floor has to do

A walk-in shower is sold as a glass panel and a drain cover. It is actually a floor. Everything that decides whether it works — whether water goes down the drain instead of across the bathroom, whether the tiles can be the size you wanted, whether the job is a morning's work or a week with a breaker — happens in the 60 to 220 mm of build-up under the tiles. If you have just bought a Maltese flat, finished or in shell, this is the detail to settle before anyone orders anything.

The fall

A level-access shower floor is not level. It is flat to the eye and sloped to the water.

Geberit specifies a fall of between 1 and 2 per cent for the tiled floor of a floor-level shower, and gives a worked example: across a 100 cm wide shower the height difference should not exceed 2 cm. Schlüter's KERDI-LINE-F set is used with a sloped tray at a 2% gradient.

Two things follow. First, these are maker figures for maker systems, not building law — we found no Maltese rule setting shower falls, so what you get is what your tiler and your drain manufacturer between them decide. Second, the fall is small enough that it is easy to lose. A 1 per cent fall over a 90 cm run is 9 mm. A tiler working to the wrong datum, or a screed laid flat and "corrected" with adhesive, eats that in one go, and the first sign is a puddle that sits by the glass for an hour after every shower.

Three places the water can go

A point drain

The classic: a round or square gully in the middle or corner of the shower, with the floor falling towards it. Geberit lists floor drains integrated into a tiled floor as one of its floor-level options.

The tiling consequence is the one people do not anticipate. Falling to a single point means four sloping planes meeting along diagonal lines — an envelope. Small tiles and mosaic take that geometry comfortably. Large-format tiles do not, because a rigid tile cannot bend across a diagonal, so every tile crossing a fold has to be cut.

A linear channel

A channel set along one edge of the shower — Geberit's CleanLine range places it close to the wall, with a comb insert to catch hair. The floor then falls in one plane, in one direction, like a very gentle ramp.

That single plane is why channels and large tiles go together: there are no folds to cut around. Schlüter's KERDI-LINE-F channel comes in lengths of 50–120 cm in 10 cm steps, in V4A stainless steel (1.4404/AISI 316L), with a 25 mm water seal, a horizontal outlet and a drainage capacity of 0.45 l/s. Geberit's channel ranges are CleanLine20, 30, 50, 60 (for thin floorings) and 80, in lengths from 30–90 cm up to 30–160 cm depending on the model, plus a tile-bearing channel where the cover takes a cut tile so the channel reads as part of the floor.

A wall drain

Geberit's CleanWall sets the drain into the wall. The floor still falls towards it, but there is no slot or grate in the floor at all, so the floor tiling stays uniform. Worth knowing about if the whole point of the exercise was an unbroken floor.

Or no tiled floor at all

Geberit also supplies shower surfaces and trays with no or low profile from 80 × 80 cm, delivered with a pre-fitted sealing fleece. The fall is built into the product. In a small flat where the floor cannot be touched, this is often the honest answer, and 80 × 80 cm is the smallest Geberit offers.

The build-up: the number that decides the job

The drain body sits under the tiles, and it has a height.

Geberit's shower channels are installed on an installation set chosen by the screed height available at the drain inlet: one set for screed heights of 90–220 mm, another for 65–90 mm. There is also a floor-penetrating installation set, where the drain passes down through the slab, and a set "with inlet". Schlüter's KERDI-LINE-F has an assembly height of 60 mm.

So the sequence in an existing Maltese flat is:

1. Find out what is actually under your bathroom tiles — screed depth at the point where the drain would go, and what is below it.
2. Compare that with the installation set the chosen channel needs.
3. If there is less screed than the set needs, you have three moves: raise the bathroom floor (which reintroduces a step at the door, unless the whole room goes up), choose a lower-build system, or go through the slab with a floor-penetrating set.

Going through the slab is where a bathroom refit turns into a structural and neighbourly question. In a flat, below your slab is somebody's ceiling. Geberit describes retrofitting a floor-level shower into an existing bathroom as generally possible — "possible" is not the same as "simple in a third-floor apartment in Sliema".

If your property is in shell form, none of this is a problem: the screed has not been laid, so the drain is set first and the screed is poured to suit it. This is the single strongest argument for deciding on a walk-in shower before the screeders arrive rather than after.

Waterproofing is not optional

Under the tiles, the shower area has to be tanked — Schlüter's channel carries a factory-fitted KERDI waterproofing collar precisely so it bonds into a sheet membrane, and Geberit's trays come with a pre-fitted sealing fleece for the same reason. For how tanking is actually done, see Tanking a Maltese bathroom before the tiles go on.

Tiles over the fall

Decide the tile at the same time as the drain, not after.

• Large formats want a single-plane fall, which means a linear channel or a wall drain.
• Small formats cope with an envelope fall to a point drain.
• Schlüter specifies that tiles bonded over its DITRA matting must be at least 5 × 5 cm, so there is a lower limit on mosaic too, at least in that system.

Buying it in Malta

Most Maltese showrooms publish no brand list, so you cannot check from your laptop who carries which drainage system — you ask, by name, and the answer is often "we can order it". We have not verified any Malta or Sicily showroom as stocking Geberit CleanLine or Schlüter drainage, and you should treat anyone's claim to the contrary as something to confirm in writing before paying.

Two local wrinkles. Sicily is a ferry ride away and frequently cheaper for the same Italian-made goods; within the EU, VAT is paid once in the country of purchase, so a Sicilian invoice is a complete invoice. And if the flat is in Gozo, every delivery crosses on the ferry, which matters more for a 160 cm channel and a pallet of large-format tiles than for a tap.

What to take to the showroom

• The screed depth at the proposed drain position, measured, not guessed.
• Whether the slab can be penetrated.
• The tile size you want.
• The shower width, so the fall arithmetic can be done in front of you: 1 to 2 per cent, no more than 2 cm across 100 cm.

Get those four right and the glass panel is the easy part.