— Chelsea advice
How Much Does a Wet Room Cost? What Sets the Price
The cost of a wet room depends less on the tiles you choose and more on what sits underneath them. The biggest price drivers are the floor (a timber floor that has to be dropped or rebuilt costs far more than a concrete one), how far the new drain is from the existing waste pipe, whether you need a shower pump or a waste pump, and how carefully the room is tanked. A wet room almost always costs more than a standard shower tray and enclosure in the same space, because the whole floor becomes the waterproof layer. Emergency Plumber Chelsea handles the plumbing side of wet rooms across SW3, SW10, Knightsbridge, South Kensington and Fulham on 020 3002 6667.
Updated July 2026 · Emergency Plumber Chelsea
Why nobody can give you a wet room price over the phone. Two bathrooms of the same size can differ enormously in cost because the work that matters is hidden: what the floor is made of, how deep the joists are, where the soil stack runs and what kind of hot water system feeds the shower. A firm quoting a fixed figure before lifting a floorboard or checking the waste route is guessing. What you can know in advance is which parts of the job drive the price, and that is what this guide covers so you can read a quote properly and compare like with like.
The floor is the single biggest cost factor. A wet room needs the drain and trap to sit below the finished floor, with the floor laid to a gentle fall toward the outlet. On a concrete or screeded floor the drain can usually be set into the screed without much disruption. Most Chelsea period houses and mansion flats have suspended timber floors, and that is where the work grows: joists may need notching or trimming, the deck is often replaced with a stronger board or a ready-made sloping former, and some rooms need the floor dropped between the joists to make room for the trap. If the joists run the wrong way for the drain, or the ceiling below has to be opened up, the labour climbs quickly.
Drain type and position come next. A point drain in the middle of the shower zone needs the floor to fall from four directions, which suits smaller tiles and costs less in hardware. A linear channel lets the floor fall in one plane toward a wall, which suits large-format tiles and usually drains faster, but the channel itself costs more and has to be set dead level. The position matters as much as the type. A drain close to the existing soil stack or waste run is straightforward. A drain on the far side of the room from the stack may need a long run under the floor with enough fall, which can mean cutting more joists or, in some layouts, is not possible by gravity at all. Our guide to moving plumbing during a renovation explains why waste routes limit where things can go.
Tanking is not the place to save money. Every wet room has to be fully waterproofed before tiling, with a liquid or sheet membrane over the whole floor and up the walls, and reinforcing tape at every corner, pipe penetration and around the drain flange. Good tanking systems cost more than cheap ones, and doing it properly takes time because liquid coats need to cure. A flood test before tiling adds a little more time but is the cheapest insurance you can buy, especially over another flat. When wet rooms fail, it is nearly always the tanking or the seal around the drain, and fixing that means taking the tiles up.
Pumps can add a noticeable amount. Two different pumps come up in wet room quotes. A shower pump, or a move to a mains-pressure system, may be needed if your flat is fed from a cold tank in the roof and a rain head would otherwise feel weak. A waste pump is needed if the wet room sits below the level of the drain it empties into, which is common in lower-ground and basement conversions in SW3 and SW10. Each adds the unit, the fitting and an electrical supply, and a waste pump also needs to stay accessible for servicing. If your flat already has a combi boiler or an unvented cylinder with good pressure, you may need neither, and our guide to mains pressure versus gravity-fed plumbing explains how to tell.
Other trades are part of the bill. A wet room is not only plumbing. There is usually an electrician for the extractor fan, lighting in the wet zone and any electric underfloor heating mat, a tiler for the floor and walls, and a glazier or supplier for a fixed glass screen. Large-format porcelain on a sloping floor takes a skilled tiler longer than standard tiles on a flat floor. When you compare quotes, check whether each one includes these trades or only the plumbing, because a quote that looks cheaper often simply leaves them out.
Chelsea-specific costs are easy to forget. In a mansion block or converted house, many leases require the freeholder's or managing agent's consent before you build a wet room over another flat, and some ask for method statements or specify the waterproofing. Parking and loading restrictions add time to deliveries and waste removal. Upper-floor flats without a lift mean carrying tiles, board and rubble up the stairs. None of this is unusual, but it adds to the labour and it should be in the quote rather than a surprise on the final invoice.
Wet room versus shower tray: what the difference actually buys. A good low-profile shower tray with a glass enclosure is usually the cheaper option, because the tray itself is the waterproof layer and only the area around it needs extra protection. A wet room costs more because the whole floor is built as a waterproof basin, and in return you get level access, an open feel and easier cleaning. If the room is small, a tray in a fully tanked shower area can give much of the look for less money. If you need level access, for example for an older relative, a wet room is often the better long-term choice. Whichever you choose, the shower area still needs tanking, and our guide to a leaking shower tray shows what goes wrong when it is skipped.
How long does a wet room take? A straightforward wet room on a solid floor, with the drain close to the existing waste, can often be completed in around one to two weeks including curing time for the tanking and adhesive. A timber floor that needs rebuilding, a long waste run, a pump installation or a ceiling to make good below will push that out. Time is money on a wet room, so the order of work matters: rough in the waste and pump, form the fall, fit the drain, tank, flood-test, then tile. Rushing the tanking to save a day is a false economy.
Ways to keep the cost down without cutting corners. Put the drain as close as you can to the existing soil stack or waste. Use a linear drain against a wall so the floor falls in one direction, which is quicker to build with larger tiles. Keep the shower valve on a wall you are already opening up. Check your water pressure early so you are not paying for a pump later. And budget properly for tanking and a flood test, because those are the parts that protect you from a much bigger bill if water gets into the floor or the flat below.
What a proper quote should list. Ask for the floor work, the drain type and make, the tanking system, any pump, the waste route, testing, and what is and is not included from other trades. A quote that says only 'supply and fit wet room' does not let you compare anything. Emergency Plumber Chelsea looks at the floor, the waste route and your hot water system first, then quotes in writing for the plumbing side before work starts. There is no call-out fee on jobs over 3 hours. For the full plumbing sequence, see our guide to wet room installation, and for the wider budget, how much a new bathroom costs. To book a survey, see our bathroom plumbing service or call 020 3002 6667.
Quick tips
- Ask what the floor is made of before anything else; a timber floor that needs dropping is where most of the extra cost sits.
- Keep the drain near the existing soil stack or waste run to avoid long under-floor runs or a waste pump.
- Never let tanking or the flood test be the saving; they are what stop a leak into the room below.
- Check your water pressure early so a shower pump or mains upgrade is in the quote, not a later extra.
- Check your lease for freeholder consent before building a wet room over another flat.
FAQs
How much does a wet room cost?
It depends mainly on the floor, the drain position, the tanking and whether you need a shower pump or waste pump. A concrete floor with the drain close to the existing waste is at the lower end. A timber floor that has to be dropped or rebuilt, a long waste run or a pumped outlet adds noticeably. A survey of the floor and waste route is needed for a firm price.
Is a wet room more expensive than a shower tray?
Usually, yes. With a tray, the tray is the waterproof layer. In a wet room the whole floor has to be tanked and laid to a fall toward the drain, which takes more materials, more labour and curing time. In return you get level access and an open, easy-to-clean room.
Can you put a wet room on a timber floor?
Yes, and most Chelsea wet rooms are on timber. The floor usually needs stiffening, a sloping former or new deck, and enough depth between the joists for the drain and trap. That extra floor work is the main reason timber-floor wet rooms cost more than concrete ones.
Do I need permission for a wet room in a flat?
Planning permission is not normally needed for an internal bathroom, but many leases require the freeholder's or managing agent's consent for a wet room over another flat. Check your lease before work starts, and keep records of the tanking and flood test.
How long does it take to build a wet room?
A simple wet room on a solid floor often takes around one to two weeks including curing time. Floor rebuilding, long waste runs, pumps or making good a ceiling below all add time.
Need an engineer in Chelsea?
Call 020 3002 6667 for 24/7 emergency dispatch across SW3, SW10 and nearby postcodes.