You install a shower in this order: first get the waste and the water pipes into the right place, then tank the walls and floor, then tile, and only after all that fit the tray, the valve and the screen. That order is not optional. Tile first and then discover the waste sits 4 centimetres too high, and you get to hack the lot back out again.
The biggest misconception on this job: that tiles are waterproof. They are not. Tiles and grout let water through, and behind your tiles sits plasterboard or plaster that cannot cope with it. The waterproofing goes underneath the tiles, and that is the part you can no longer see once it is finished. Which is exactly why it gets skipped, and exactly why the neighbours’ bathroom floor is rotting five years from now.
Below is the whole story: which type of shower to choose, how much space you need, how to get the waste at the right height (the real stumbling block), how to tank with sealing tape and waterproofing slurry, which valve to pick, what the rules are for ventilation and sockets in a bathroom, what it costs and which ten mistakes to avoid.
First decide: shower tray, wet room or ready-made cubicle?
| Tray with enclosure | Wet room with gully or channel drain | Complete cubicle (ready made) | |
|---|---|---|---|
| Floor build-up needed | Little, the tray sits on the floor | A lot: 8 to 15 cm below the tiled floor | Little |
| DIY-able | Very doable | Tricky, the tanking is critical | Easiest |
| Level access | No, usually a step up | Yes | No |
| Risk of leaks | Low | Higher, demands proper work | Lowest |
| Cost | Medium | High | Low to medium |
| Cleaning | Cleaning a tray is simple | More grout, more limescale | Easy |
A shower tray is the safest choice for a self-builder. The tray itself is waterproof, so your tanking only has to cope with the walls and the tray-to-wall joint. Pick an acrylic tray (light, warm to the touch, cheaper) or one in stone resin or composite (heavier, sharper looking, dearer, and often cuttable to size).
A wet room looks better and gives you level access, but it is an entirely different sort of job. You need floor build-up for the gully or channel, you have to get the whole floor to fall, and your tanking has to be sound across every square centimetre. Reckon on more preparation time and, if the existing floor sits low, on raising the whole bathroom floor.
A complete cubicle with its own base and walls is the fastest and the least risky. Just connect it to the waste and the water. Not the prettiest option, but the most practical in a rented place, a second bathroom or a loft shower.
Not sure? If you are doing it yourself and you have little floor build-up available: tray.
Sizes: how much space do you really need?
Practical dimensions to work with, not legal requirements.
- Smallest workable shower: 80 by 80 centimetres. Tight, but it works.
- Comfortable: 90 by 90 up to 100 by 100 centimetres.
- Genuinely nice: 90 by 120 centimetres or bigger. You can bend down without touching the wall.
- Clear space in front of the shower: keep at least 60 centimetres so you can dry off and open the door.
- Shower head height: 200 to 220 centimetres for a rain head, 190 to 210 centimetres for a normal riser rail at its top.
- Valve height: a thermostatic valve usually sits 100 to 110 centimetres above the gully or the tray rim.
- A corner works best: you already have two walls, you only need one or two glass panels, and the pipework can live in those two walls.
Step 1: the waste, and why it decides your whole plan
This is where the job is won or lost. Do this before you order anything else.
Measure the height you have. Work out how much room sits between the top of your structural floor (concrete or timber joists) and the top of your finished tiled floor. That is your room for manoeuvre for the waste.
- For a shower tray you need very little: a shallow shower trap often fits in 8 to 12 centimetres under the tray, and the tray itself goes on a built or timber base with space for that trap inside it. If you cannot get below the floor, you simply set the tray higher on a plinth with a step.
- For a wet room you need a gully or a channel drain. There are extra-shallow versions with a build-in depth of around 6 centimetres, but as standard reckon on 8 to 15 centimetres of build-in height plus room for the waste pipe to fall. In a home with a concrete floor you cannot cut into, that is often exactly why a wet room is impossible without raising the entire floor.
Diameter. For a normal shower a 40 millimetre waste pipe is standard. With a big rain head or a twin outlet, 50 millimetre is the better call, because there is simply more water per minute coming down. If you are hesitating: take 50. The extra cost is negligible, and a shower that will not drain is a daily irritation.
Fall on the waste pipe. Reckon on roughly 1 centimetre of fall per metre of run towards the soil stack. UK guidance for a 40 millimetre branch allows anything between about 18 and 90 millimetres per metre, so a bit steeper does no harm. Too little fall and the water stands; far too much and the water runs away while the muck stays behind.
Trap seal. Every shower waste needs a trap that keeps drain smells out. The European standard EN 1253 for gullies works to a minimum trap seal of 50 millimetres. Extra-shallow traps with a lower seal do exist, but then the seal dries out faster in a shower you do not use for weeks. And then you smell it.
Always do a leak test. Connect everything, plug the waste, pour in a bucket of water and leave it an hour. Better still: run the tap into it for ten minutes and look underneath. This is the last time you can get to it.
Step 2: the water supply
Feed pipes. Hot and cold to the valve, usually 15 millimetre copper or a plastic pipe system. The centre-to-centre distance between hot and cold is 150 millimetres as standard, and hot goes on the left, cold on the right (as you look at the valve). Stick to that, even if you are fitting a concealed valve yourself, otherwise the next valve will not fit onto it.
Concealed or exposed. A concealed thermostatic valve looks clean, but the body has to go into the wall before you tile, and the fitting depth has to be spot on. If the body sits 1 centimetre too deep, your cover plate will not meet the tile. An exposed bar valve is far more forgiving and much easier to replace later. For a first shower: exposed.
Pressure test before you close up. Put the pipes under pressure, or at least leave them at normal mains pressure for a few hours and check every joint. Hunting for a weeping joint behind your new tiles afterwards is the kind of day that does nobody any good.
Hot water: can you actually deliver it? A normal shower runs fine off a system with enough output. In the Netherlands boilers carry a CW class for this: a CW4 combi delivers at least 7.5 litres a minute at 60 degrees, which is enough for an ordinary shower, and for a rain head or two outlets you want CW5 or higher. In the UK a combi is rated in litres per minute at a 35 degree temperature rise, and a typical one gives 10 to 15. Going from a normal head to a rain shower? Check this first, otherwise you have a beautiful shower that turns lukewarm the moment somebody opens the kitchen tap.
Want to recover the heat? This is the moment to consider waste water heat recovery. The waste pipe is open anyway. A unit like that in the waste preheats your cold incoming water with the heat of the shower water running away. Retrofitting one afterwards almost always means breaking the floor open again.
Step 3: tanking, the part nobody sees
This is where DIY jobs go wrong most often. To be blunt: tiles and grout are not waterproof. Cement grout absorbs water. Silicone ages and cracks. So underneath the tiles there has to be a waterproof layer that stops the water coming through. In the UK this is normally called tanking, and BS 5385 covers tiling in wet areas.
What you need:
- Waterproofing slurry or a liquid tanking membrane (brush or roller applied, usually in two coats)
- Sealing tape (flexible waterproofing tape) for every corner and junction
- Preformed collars for pipe penetrations
- Possibly a tanking membrane or tile backer boards on a timber substrate
Where it has to go:
- Every floor-to-wall corner in the shower area, running at least 20 centimetres either side
- Every vertical internal corner in the wet zone
- Around the gully or channel drain, with a collar or a proper connection piece
- Around every penetration: valve connections, shower head outlet, glass panel fixings
- The whole wet zone, fully covered: the shower floor and the walls to at least 20 centimetres above the highest shower head, which in practice means the whole wall
How you do it:
Make sure the substrate is clean, dry, dust free and sound. Prime it if the manufacturer says so (on plaster and porous substrates, always). Then a generous bed of slurry into the corners, press the sealing tape into it without air bubbles, and overlap each length of tape onto the next by at least 5 centimetres. After that the flat areas, fully covered, in two coats, and only start the second coat once the first is dry. Let the lot cure as the packaging says before you start tiling. That waiting feels like wasted time. It is not.
On a timber substrate: timber moves, and plaster in a shower is asking for misery. Use cement-based tile backer boards or a proper wet room board, fix them firmly to a stiff enough substrate, and seal the joints as part of the tanking.
On a timber floor: a joisted floor flexes. Tiles and flex get along badly. Stiffen the floor (double boarding, extra noggins) or go for a prefabricated shower floor former that is rated for laying on joists.
Step 4: tiling and the fall in the floor
Shower tray: you do not have to create any fall, the tray does that itself. All that matters is that the tray sits level and is supported everywhere.
Wet room: the whole shower floor runs down to the gully or channel. Reckon on roughly 1 to 2 percent of fall, so 1 to 2 centimetres per metre. With a central gully the floor falls towards the middle from four directions. With a channel along the wall or by the door it falls in one direction. That second one is far easier for a self-builder to get right, because you only have to lay one plane to a fall instead of four.
Tile size: big tiles on a floor with a fall are difficult, because a large tile cannot follow a curve. With a central gully you work with smaller tiles or mosaic. With a channel drain you can use bigger formats.
Slip resistance: choose a tile for the shower floor with a slip rating (R10 or higher, or class B/C for barefoot areas). In the UK you will often see this quoted as a pendulum test value, where 36 or more when wet is the usual benchmark. A polished tile in a shower is an accident waiting for a date.
Grout: use a grout suitable for wet areas, and finish moving joints (corners, the junction with the tray) with sanitary silicone, not grout. Silicone is meant for places that move, grout for places that do not.
Step 5: fitting the shower tray
- Mark out the outline of the tray on the floor and check it fits, including any profiles from the glass panel.
- Build the base. Plenty of trays have no adjustable feet, in which case you build a solid base from aerated concrete blocks or timber battens cut to size. Build inside your marked lines, so the tray drops over it and the rim sits clear.
- Check it is level. Along the length and across the width, and then once more. A tray that is not level holds water at the rim.
- Connect the waste and test it now, with the tray sitting loose on top, before you reach for the silicone.
- Apply silicone to the top of the base and everywhere the tray bears on it.
- Set the tray and weight it down. Put two bags of at least 25 kilos in the tray and leave it 24 hours so the silicone cures and the tray makes contact all over.
- Seal between tray and wall with a clean bead of sanitary silicone. Work with sealant profiles or masking tape for a straight line, and pull the tape off while the silicone is still wet.
- Leave it 24 hours to cure before you shower.
A tip that saves a lot of grief: make the underside of the tray reachable. Put an access panel into the built-up front, or use a clip-on front panel. One day that trap will leak or block, and you do not want to be getting at it with a bolster chisel.
Step 6: valve, glass screen and final fit
A thermostatic valve is worth it. It holds the temperature steady when water is drawn off elsewhere, and it has a safety stop at around 38 degrees. With children in the house that is not a luxury.
Glass screen: use safety glass of at least 6 millimetres, and on a free-standing panel preferably 8. Drill the tiles with a tile bit at low speed with the hammer action off, and use fixings suited to your wall type. Seal every drilled hole in the wet zone with silicone before the plug goes in. Water that gets behind your tiles through a screw hole never comes back out.
Shower head and riser rail: fit the rail on the side where you can reach the controls without standing under the spray.
Waste grate: check that the grate comes out for cleaning. Hair is the number one cause of a sluggish shower waste.
The rules: ventilation and electrics
Two things that get forgotten a lot and that genuinely matter.
Ventilation. In England and Wales, Approved Document F asks for an intermittent extract rate of 15 litres per second in a bathroom, which is around 54 cubic metres an hour. The Dutch requirement sits at 14 dm³/s, roughly 50 cubic metres an hour. Same ballpark, and it is not a luxury: all the water vapour you generate in the shower has to get out. Without extraction you get mould on the grout, in the corners and behind the cabinets. If all you have is a window, in practice you will not hit that rate reliably. Sort out the make-up air too: an extractor that cannot draw anything in (a gap under the door, a transfer grille) does very little.
Electrics. BS 7671 works with zones in the bathroom:
- Zone 0 is inside the bath or the shower tray itself. Only special, waterproof equipment on extra-low voltage.
- Zone 1 is directly above the bath or shower tray up to 2.25 metres above finished floor level. No normal sockets or switches.
- Zone 2 is the 0.6 metre strip around zone 1, also up to 2.25 metres high. Here you need at least splash-proof equipment (IPX4).
- Every circuit serving the bathroom sits behind 30 mA RCD protection.
In practice the UK rule is stricter than the Dutch rule of thumb of 60 centimetres: socket-outlets have to be at least 3 metres horizontally outside the zone 1 boundary, with shaver supply units and SELV circuits as the exceptions. Have bathroom connections done by somebody who knows what they are doing. In England and Wales most of this work is notifiable under Part P of the Building Regulations. A shower room and electricity is not the place to experiment.
What does installing a shower cost?
Ranges to work with, including VAT, excluding stripping out the old setup.
| Item | DIY (materials) | Have it done |
|---|---|---|
| Shower tray (acrylic, 90×90) | 100 to 300 euros | same plus labour |
| Stone resin/made-to-measure tray | 250 to 700 euros | same plus labour |
| Shower gully or channel drain | 100 to 500 euros | same plus labour |
| Glass screen or enclosure | 150 to 800 euros | same plus labour |
| Exposed thermostatic valve | 100 to 300 euros | same plus labour |
| Concealed thermostat + valve body | 200 to 600 euros | same plus labour |
| Tanking (slurry, tape, collars) | 75 to 200 euros | included |
| Tiles for the shower area | 25 to 80 euros per m² | included |
| Altering pipework and waste | 75 to 250 euros | 300 to 900 euros |
| Waste water heat recovery | 700 to 1,400 euros | 900 to 1,800 euros fitted |
| Complete shower replacement, done for you | 2,000 to 5,000 euros |
Doing it yourself saves you roughly half, and most of that sits in the tiling and the plumbing.
Ten mistakes that cost you money
- Reversing the order. Waste and pipes first, then tanking, then tiles, then the sanitaryware. Always.
- Thinking tiles are waterproof. They are not. There belongs a waterproof layer underneath them.
- Not measuring the floor build-up you have before ordering a wet room gully. The gully simply will not fit.
- Not doing a leak test before everything gets closed up.
- Not supporting the tray. Acrylic trays resting only on their rims will creak and eventually crack.
- Using silicone as waterproofing instead of as a finish.
- Not sealing drilled holes in the wet zone before the plug goes in.
- Not creating any access to the trap.
- Forgetting the ventilation. Your new bathroom will be mouldy along the grout within two winters.
- Showering too soon. Silicone and tanking really do need their curing time. One day of patience against years of enjoyment.
Frequently asked questions
Can I install a shower myself?
A tray with an enclosure or a glass screen is very doable for a handy DIYer, certainly if the waste is already roughly in the right place. The hard parts are getting the waste to the right height and getting the tanking sound. A level-access wet room in an existing bathroom is a good deal harder and needs floor build-up that often is not there. Bathroom electrics you have done for you.
How high should the waste for a shower be?
That depends on what you are fitting. With a tray a shallow trap often fits in 8 to 12 centimetres underneath it, and otherwise you put the tray on a plinth. With a wet room you need a gully or channel; extra-shallow versions start around 6 centimetres of build-in height, but realistically reckon on 8 to 15 centimetres plus room for the fall on the waste pipe. Measure this first, because it decides whether your plan is feasible at all.
What diameter waste do I need for a shower?
For an ordinary shower 40 millimetres is standard. If you have a big rain head, a main head plus a handset, or a waste that runs a fair distance, go for 50 millimetres. Keep roughly 1 centimetre of fall per metre towards the soil stack.
Do I need to tank my bathroom underneath the tiles?
Yes, in the wet zone you do. Tiles and grout let water through and the substrate behind them usually cannot cope. A system of waterproofing slurry or a liquid membrane with sealing tape in every corner, at every penetration and around the gully is the standard. It is not written into the Building Regulations in so many words, but manufacturers and insurers assume it in practice, and without it a leak is only a matter of time.
How much space do I need for a shower?
From 80 by 80 centimetres it is workable, 90 by 90 is comfortable, and from 90 by 120 you can bend down properly. On top of that, keep roughly 60 centimetres of clear space in front of the shower so you can dry off and open the door.
Can I have a socket next to the shower?
Not in zone 0 or zone 1 (in and directly above the shower up to 2.25 metres), and in zone 2 only in a splash-proof version. In the UK socket-outlets have to sit at least 3 metres horizontally outside zone 1, and everything sits behind a 30 mA RCD. Have this work done by somebody who knows BS 7671.
Do I need an extractor fan in the bathroom?
Yes. A bathroom is worked to an extract rate of 15 litres per second in England and Wales, roughly 54 cubic metres an hour, and the Dutch figure of 14 dm³/s comes out at about 50. A window on its own will not deliver that reliably in practice, certainly not in winter when you keep it shut anyway. Make sure air can get in as well, otherwise your fan is pulling against a closed door.
The short version: measure the floor build-up you have first, because that decides whether it becomes a tray or a wet room. Then lay the waste to a fall with a proper trap seal, test for leaks before you close anything up, tank the wet zone across the whole surface with slurry and sealing tape, tile with a slip-resistant floor, set the tray fully supported and dead level, and sort out the ventilation.
Do that, and you have a shower that lasts twenty years without you ever having to think about what is going on behind those tiles.
Are you tiling, plastering or building up the walls for this bathroom yourself? At Koning van je Woning you will find worked-out instructions for walls, tiling and finishing, so you know exactly what order to work in and where it tends to go wrong. Have a look.
Regards from Fred Schouten, handyman and DIYer through and through
PS: before you run a silicone bead, lay two strips of masking tape along the joint, gun the silicone in between, smooth it off and pull the tape straight off while the silicone is still wet. You get a silicone line that looks like a professional set it, and it costs you two minutes extra. Small tip. Big difference.