Ask ten London contractors what a bathroom renovation costs and you will get ten different answers, because the price depends far more on the room and the decisions you make than on the word "bathroom". Rather than publish a price list that would be wrong for most homes, this guide explains what actually drives the cost, how a good quote is put together and how to compare quotes fairly. Every GMAS bathroom is quoted in writing after a visit, and the price is agreed before work starts.
What drives the cost of a bathroom renovation
Size and layout
Floor area matters less than people expect. What drives labour is the amount of tiling, the number of fittings and how awkward the room is to work in. A small London bathroom with a sloping ceiling, a boxed-in soil stack and a window in the wrong place can take longer than a larger, simpler room.
Moving the toilet, bath or shower
Keeping the existing layout is the single biggest saving. Moving a toilet means moving the soil connection, which in a suspended timber floor may be straightforward and in a flat with a concrete floor may not be possible at all. Moving a shower or bath means new waste runs with enough fall to drain properly.
Strip-out and what is behind the tiles
Nobody knows the condition of the walls and floor until the old bathroom comes out. Blown plaster, rotten floorboards from a slow leak, or old lead or iron pipework all add work. A good contractor allows for this honestly in the quote rather than surprising you halfway through.
Tiles: area, format and pattern
Full-height tiling costs more than tiling the wet areas only. Large-format porcelain needs flatter walls and more care to lay. Small mosaics, herringbone and patterned layouts take longer than standard rectangular tiles, and the tile price itself varies hugely.
Showers, wet rooms and waterproofing
A walk-in shower or wet room needs the floor laid to falls towards the drain and fully tanked with a waterproof membrane. It is more work than fitting a tray and enclosure, and it must be done properly, because tiles and grout are not waterproof on their own.
Sanitaryware, brassware and storage
The suite, taps, shower valve, screen and vanity unit can range from budget to designer. Concealed cisterns, wall-hung units and built-in storage need studwork or framing behind them, which adds labour as well as materials.
Electrics, heating and ventilation
Electric underfloor heating, heated towel rails, lit mirrors, shaver sockets and new lighting all need electrical work. Bathrooms are a special location under the wiring regulations, and some work is notifiable under Part P of the Building Regulations. An extractor fan that meets Part F ventilation requirements is essential to prevent condensation and mould.
London factors that affect the price
- Access: top-floor flats without a lift, narrow stairs and no space to store materials all slow the job down.
- Parking and the congestion charge: permits, pay and display and the central London charge are real costs for every day on site.
- Waste: skips often need a permit on the road, and many London streets have no room for one, so waste is removed by van instead.
- Flats and leases: many leases restrict working hours and require the freeholder's consent for alterations, especially anything affecting the floor or the soil stack.
- Older buildings: period properties often need extra work to bring pipework, wiring and floors up to standard.
How a bathroom quote should be structured
A quote you can rely on is itemised, so you can see what each part of the job involves. It should list the strip-out and disposal, any plumbing and waste alterations, plastering or boarding, waterproofing, tiling, electrics, fitting of the suite and decoration. Two terms are worth understanding:
- Prime cost sums are allowances for items you have not chosen yet, such as tiles or taps. If you choose something dearer, the price goes up; cheaper, it comes down.
- Provisional sums are allowances for work that cannot be priced until it is uncovered, such as replacing rotten joists. They should be clearly marked, with a sensible amount, not used to keep the headline figure low.
The quote should also state who supplies the sanitaryware and tiles, how long the bathroom will be out of action, and the payment stages.
Questions to ask before you accept
- Is the waterproofing included, and what system will you use?
- Who carries out the plumbing and electrical work, and are they registered where the work requires it?
- What happens if you find rot, leaks or damaged plaster once the old bathroom is out?
- How many working days will we be without the bathroom?
- Are making good, decoration and waste removal included?
- What is excluded?
How to compare quotes like for like
Lay the quotes side by side and check they cover the same scope: the same layout, the same extent of tiling, the same waterproofing, and the same allowance for materials. A quote that looks cheaper often leaves out tanking, decoration or the electrics, or relies on large provisional sums. Ask each contractor to price the same specification and you will see the real difference.
Ways to control the budget
- Keep the toilet and waste in the same position.
- Tile the wet areas fully and paint the rest with a bathroom-grade finish.
- Choose standard-sized tiles in a simple layout.
- Pick freestanding furniture rather than bespoke built-in storage.
- Do the bathroom at the same time as other work, such as a full refurbishment or rewire, so trades are only on site once.
How a GMAS bathroom quote works
- Visit: we measure the room, check the services and talk through what you want.
- Written fixed quote: itemised, with any allowances clearly marked.
- Selections: you choose the suite and tiles, and we can help source them.
- Works: one point of contact project-manages every trade in the right order.
- Handover: we check everything with you before we finish.
See our bathroom renovation service or call 07498 597339 for a written quote.
Frequently asked questions
Do I need building regulations approval for a new bathroom?
Replacing a bathroom like for like does not usually need approval, but some electrical work is notifiable under Part P, new drainage and ventilation must meet the regulations, and structural changes need approval. We tell you what applies before work starts.
How long does a bathroom renovation take?
A like-for-like refit is usually around a week or two. A new layout, a wet room or a bathroom that needs repairs behind the walls takes longer. Your quote states the expected number of working days.
Can I supply my own sanitaryware and tiles?
Yes. Tell us before we quote so the price reflects labour only for those items, and so we can check the quantities and that the products suit the room.
Will there be extras once work starts?
Only if something is found that could not be seen before, such as rot or a hidden leak, or if you change the scope. Anything extra is explained and agreed in writing before it goes ahead.
Is a wet room more expensive than a shower enclosure?
Usually yes, because the floor has to be laid to falls and the whole area tanked. In a small bathroom it can still be the best use of space.