How to Build a Level-Access Wet Room: Formers, Wastes, Tanking and Thresholds

A level-access wet room is a shower with no tray lip and no step — the floor of the showering area sits flush with the rest of the bathroom floor and falls gently to a waste. It looks simple. It is not difficult, but it does depend on four components working together, and getting one of them wrong is how wet rooms leak.

This guide covers what those four components do, how to choose each one, and the decisions people most often get wrong.

The four components

1. The former — a pre-graded tray that sits into the floor and creates the fall to the waste
2. The waste — the drain assembly that takes the water away
3. The tanking — the waterproof membrane over the former and surrounding floor and walls
4. The threshold — an optional edge strip that defines the showering area and holds water in it

Skip the tanking and you have a wet floor with a hole in it. Skip the threshold and water travels further across the floor than you might want. The former and the waste are the two that must be matched to each other.

1. Choosing a former

Formers differ in material, thickness, strength and the waste they take. The three main options we stock:

Tuff Form

Tuff Form is the workhorse. Composite construction, 22mm deep, trimmable to within 150mm of the waste, and suitable for both tiled and vinyl finishes. The ribbed underside stops it sliding or floating during installation. If you are fitting a level-access shower in a standard timber-floored bathroom and want the straightforward option, this is it.

Tuff Form8

Tuff Form8 is the heavier-duty version, built for higher traffic and multi-user environments where the floor takes more punishment.

TriForm

TriForm is the premium option and behaves differently. It is hand-laid GRP, 22mm thick, and carries up to 254kg. Instead of a central circular waste it uses a linear gulley — a discreet slot rather than a round grate — fed by four gradient planes. Three waste positions are built into an integral trough, so you can move the outlet to miss a joist without cutting the former about, and using more than one outlet pushes drainage up to 78 litres per minute. That is the figure that matters if a drench or power shower is going in.

The TriForm also takes tiles up to 25mm thick and has a reversible waste cover: tile it to match the floor, or flip it for brushed stainless steel.

2. Choosing a waste

The waste must match both the former and the floor construction. Two numbers govern the choice: the water seal depth and the depth below the former.

• GW19 — 19mm water trap, 50mm threaded outlet, roughly 93mm below the mounting surface. The usual choice for timber floors where joist depth is limited.
• GW90 — deeper 90mm option for low profile applications, with a low depth version where clearance is tight.
• TF75 — one-piece gravity waste designed for vinyl floor finishes.

A deeper water seal performs better against drain odours but needs more depth below the floor. Measure the void before you order, not after. Browse the full set in Wet Floor Former Wastes.

3. Tanking: the bit people skip

Tanking is the waterproof layer applied over the former, the surrounding floor and the lower walls before tiling. The former itself is waterproof; the joint between the former and the floor is not, and neither is a tiled surface. Grout is porous. Without tanking, water tracks through the grout, under the tiles and into the floor structure, and the first sign of it is a stain on a ceiling below.

Two systems:

• FormSafe is a self-adhesive pre-formed membrane — a 1mm rubberised sheet with a fabric mesh face. The 5m² kit includes a 5m x 1m roll, 500ml primer, 10m reinforcing tape and 290ml jointing compound. It is ready to tile immediately with no drying time, which is its main advantage on a tight programme. A 10m² kit covers larger rooms.
• Mapei is the liquid-applied alternative — painted on, needs curing time, but easier to work around awkward shapes and pipe penetrations.

Whichever you choose, the reinforcing tape at the former-to-floor joint and at every internal corner is not optional. That is where failures happen.

4. Thresholds

A threshold is a low aluminium strip that defines the showering area. It screws to the finished floor and seals with silicone, and because the profile is shallow it acts as a gentle ramp rather than a step — the floor stays level-access.

You do not strictly need one. You want one if the bathroom floor is large, if the fall is modest, or if there is no screen to contain spray. AKW threshold kits come straight at 2000mm, or L-shaped to wrap two edges of the showering area, in seven sizes with left and right hand options. There is a made-to-measure option for anything non-standard.

They are compatible with all AKW formers and can be used alongside a screen rather than instead of one.

The kit route

Matching a former, a waste cover, a waste and a tanking system means four separate decisions and four chances to order something that does not fit. The AKW Freelux Wet Room Kit bundles them: a TriForm former in your chosen size, the gulley waste cover, a GW19 gravity waste and a full 5m² FormSafe tanking kit with accessories.

It comes in 900 x 900mm, 1000 x 1000mm, 1300 x 820mm and 1200 x 1200mm, with a choice of gulley cover for 6-16mm or 16-25mm tiles.

There is also the Essential Bathrooms DFG Wet Room Kit, which goes further and adds an electric shower, grab rails, curtain rail and curtains — built around the specification typically funded through a Disabled Facilities Grant.

Getting the floor right

The former has to finish flush with the surrounding floor. On a timber floor that usually means the former sits between or on the joists and the rest of the floor is built up to match with plywood or backer board.

Both the Tuff Form and TriForm formers are 22mm thick, which is sized to suit an 18mm UK timber floorboard plus 4mm plywood — the most common UK build-up. If your existing floor is a different thickness, that difference has to be packed out or the floor level adjusted before the former goes in. Check this first. It is the measurement that causes the most problems on site.

On a concrete floor the former is bedded into a recess or the surrounding floor is screeded up to it. Allow the screed to cure hard before tanking.

Tile thickness and the waste cover

On the TriForm, the gulley cover is specified by tile thickness — 6 to 16mm, or 16 to 25mm. Measure the tile itself, not the tile plus adhesive bed. Standard ceramic and porcelain almost always fall in the first band; natural stone and thick large-format porcelain fall in the second.

Getting this wrong means a cover that sits proud of or below the finished floor, and it is not adjustable after the event.

Five things that go wrong

1. No tanking, or tanking without taped joints. The most common and most expensive failure.
2. Waste too deep for the void. Measure below the floor before ordering.
3. Floor build-up not matching the former. Leaves a lip, which defeats the point.
4. Cutting the former too close to the waste. Each former has a minimum — 150mm on Tuff Form, 100mm on TriForm. Past that you compromise the structure.
5. Wrong gulley cover for the tile. Not fixable once tiled.

Where to start

If you know your sizes, browse Wet Floor Formers, Wastes and Tanking Kits, or see everything together in Wet Rooms.

If you are not sure what fits your floor, send us the room size, the floor construction and the depth available below it, and we will put the specification together for you.