Wet Room Installation Step by Step

Before anything is stripped out, we need to know what is under the existing floor. Timber joists, concrete slab, and the depth available between the joists or slab and the finished floor level all change how the job is done. On a timber floor, dropping a drain in usually means notching or dropping joists, which needs to be done properly so the floor still carries its load. On a concrete slab, you are usually cutting into the slab itself to set the drain low enough, which is noisier and messier but often more straightforward long term.

This is also when we work out the fall, meaning how the floor slopes towards the drain. A wet room needs a consistent gradient from every direction so water actually runs to the drain rather than pooling. Getting this wrong is one of the most common failures in DIY or rushed wet rooms, where the floor looks flat but water sits in a corner because the fall was never checked properly with a level. We mark out doorways, thresholds and any step down at this stage too, because retrofitting a threshold detail after tiling is a poor compromise.

There are two main ways to build the sloped floor. A preformed wet room tray or former is a rigid, pre-sloped board that sits on the subfloor and already has the fall built in around a central or edge drain. It is quick to fit, consistent, and reduces the risk of getting the gradient wrong on site. The alternative is a graded screed, mixed and laid by hand to fall towards the drain, which takes longer and depends heavily on the skill of whoever is doing it, but gives more flexibility for awkward shaped rooms or unusual drain positions.

What can go wrong here is straightforward but common. A former that is not bedded down solidly can flex underfoot, which cracks tiles and grout lines over time. A screed that has not been mixed or cured correctly can develop hollow spots, which you sometimes hear as a slightly different sound when you tap the tiles later. We always check the fall with a spirit level in several directions before committing to tanking, because once the waterproofing goes on top, correcting the fall means starting again from the floor structure.

The drain itself needs to be sized and positioned properly, not just dropped in wherever is easiest. Linear drains along one wall are popular now because they are less visually intrusive and give a cleaner look, but they need the fall calculated correctly along their whole length, not just towards a single point. Point drains in the centre or a corner of the room are simpler and more forgiving of small errors in the floor build up.

Whatever type is used, the connection to the waste pipe below needs enough fall of its own to clear water away without the pipe running uphill anywhere, and it needs to be accessible for future maintenance, even if that access is just knowing where it is under the floor rather than a visible hatch. A drain that blocks and cannot be reached without lifting tiles is a design failure, and it is one we see in older or badly planned wet rooms fairly often.

Tanking is the waterproof membrane system applied to the floor and walls before any tiling happens. It usually involves a liquid or sheet membrane, reinforced with waterproof tape at every joint, corner, and penetration such as pipework or the drain itself. This layer is what actually stops water getting into the floor or wall structure. The tiles and grout on top are not waterproof on their own, they are decorative and protective, but water will find its way through grout lines over time, and the tanking underneath is what stops that becoming a problem.

The most common failure point in tanking is corners and pipe penetrations, because flat membrane on an open wall is easy to apply well, but detailing around a pipe or an internal corner needs care and the right tape or corner pieces. We check every joint and penetration is properly sealed before moving on, because once tiles are down, a gap in the tanking is invisible until damp starts showing on a ceiling below or a skirting board starts to lift.

With the tanking tested and dry, tiling can begin. Floor tiles in a wet room are usually smaller format than you would use on a normal bathroom floor, because smaller tiles with more grout lines cope better with the curved fall towards the drain without needing to be individually cut into wedge shapes. Wall tiles have more flexibility in size and layout, though large format tiles need a flatter wall than older properties sometimes provide, which can mean extra prep work.

Once tiling is finished, all the movement joints, meaning where the floor meets the wall, around the drain, and at any corners, need to be sealed with silicone rather than grout, because silicone can flex slightly with the building's natural movement while grout cannot. This is a small detail but it is where a lot of leaks start if it is skipped or done with the wrong product. We always use a mould resistant sanitary silicone in these joints rather than standard grout, and where the sealant meets the tanking layer beneath, the two need to be compatible so they bond properly.

Before we consider a wet room finished, we run water into it, both from the shower and directly onto the floor, and watch how it drains. This should show water flowing cleanly towards the drain from every part of the room, with no pooling in corners or against thresholds. We also check the room from below or from an adjoining space where possible, looking for any sign of dampness coming through, though with a properly tanked floor this should never happen.

Handover includes explaining anything the household needs to know, such as which cleaning products to avoid on the tiles and silicone, and roughly how often the sealant around penetrations should be checked. A wet room that has been built correctly should give years of trouble free use, but it is not entirely maintenance free, and knowing what to look out for early saves a much bigger job later.

If you are thinking about a wet room conversion anywhere around Gloucester, Cheltenham, Tewkesbury, Stroud, Newent or the Forest of Dean, we would rather talk through the practicalities of your specific floor and layout before quoting than give you a number that does not reflect what your house actually needs. Every wet room starts with a proper look at the floor structure, because that decides most of what follows.

We handle the plumbing, tanking, tiling and fitting ourselves rather than subcontracting parts of it out, which means one team responsible for the whole job and no gaps between trades where problems can hide. Call us on 07927 593 585 or get in touch through /contact for a free, no obligation written quote and a home visit to talk through your options.