Wet rooms, built watertight

In a wet room the shower isn't a box sitting on the floor. The floor itself is the shower tray. That means three things have to be right. First, the whole wet zone has to be waterproofed, or tanked, with a membrane system that runs across the floor and up the walls. Second, the floor needs a gentle, consistent fall towards the drain so water heads the right way instead of sitting in puddles. Third, the drain has to be sized and positioned so it can take everything the shower throws at it.

Get any of those wrong and the problem is hidden until it isn't: a brown stain on the ceiling downstairs, a bouncing floor, or grout that never quite dries. That's why we treat wet rooms as a construction job first and a tiling job second.

Most Southside homes have timber floors upstairs, and every tenement flat above the ground floor does. Timber moves, and tiles and waterproofing hate movement. So before anything else we check the joists, their size, condition and spacing, and whether anyone has notched them for old pipework over the years. Then we build a rigid, flat deck to take the wet room. On a timber floor that usually means a purpose-made wet room former or a sloped board system laid between or over the joists, fixed down solidly.

The depth of the joists also decides what drain you can use. A standard gully needs more depth than some old floors can give. In a tenement that can mean a shallow-trap drain, a linear channel drain along one wall, or a slightly raised floor in the shower zone with a gentle ramp. On a concrete ground floor we may need to break out a channel for the waste and screed back to falls. None of this is guesswork. We look at your floor at the survey and tell you which route suits your room.

Tanking is the waterproof skin of the room. We use a complete manufacturer system: primer, membrane, tapes for the corners and junctions, and collars around the pipes and the drain. Following one system matters, because mixing products is how corners fail. In the shower zone the waterproofing goes up the walls well above the spray line, and in a full wet room it covers the whole floor.

Once the tanking has cured we check it before a single tile goes down. You can't see waterproofing after the room is finished, so this is the step that protects your ceilings and your neighbours' ceilings. It's also why a wet room typically takes longer than a standard refit. Some of those days are simply waiting for products to cure properly.

A big overhead rose looks brilliant in a brochure. Whether it works in your house depends on your water supply. Before we recommend a shower we check your pressure and flow and find out whether you're on a combi boiler, a cylinder, or an old tank in the roof space, which some top-floor tenement flats still have. If the pressure isn't there, we'll suggest a shower that performs with what you've got rather than promising a deluge you'll never get.

The drain has to keep up with the shower too. A linear drain along the back wall lets you use large-format tiles with a single fall, which looks clean and is easy to keep. A centre drain gives an 'envelope' fall that needs smaller tiles or careful cuts. We'll talk you through both.

Wet rooms are brilliant for small bathrooms because losing the tray and the enclosure makes the room feel bigger. They're easy to clean and they're level access, which helps if anyone in the house has mobility problems now or might in future. A fixed glass screen keeps the spray off the toilet and your towels, and a decent extractor fan plus a heated towel rail or underfloor heating stops everything staying damp. Put the toilet roll holder out of the splash zone. You'll thank us.