Bathroom renovation cost calculator
Bathrooms are small rooms with six trades in them. The cost is driven far less by the suite you choose than by what is behind the tiles.
Last updated July 2026 · built by working UK builders
Cheap bathrooms fail at the joints. Tanking, a properly bedded tray and a real extractor cost a few hundred pounds and save you the whole ceiling below.
Any electrics in a bathroom are notifiable work under Part P — you want the certificate.
The rates behind this calculator
All figures are 2026 UK prices for a competent, insured, VAT-registered contractor. Costs are shown as ranges because building work is delivered in ranges. A “×” value multiplies the whole build cost.
What are you doing?
| Option | Cost | Effect on total |
|---|---|---|
| Cosmetic refresh New taps, shower, seals, paint — keep the layout and tiles | £1,200–£3,000 | Added |
| Full replacement, same layout Strip out, new suite, new tiling, same pipe positions | £5,500–£11,000 | Added |
| New layout Moving the bath, basin and WC to new positions | £8,000–£16,000 | Added |
| Creating a new bathroom or en-suite In a bedroom, loft or box room — no plumbing there now | £9,000–£18,000 | Added |
Specification
| Option | Cost | Effect on total |
|---|---|---|
| Budget High-street suite, ceramic tiles | — | ×0.72 |
| Mid-range Branded brassware, porcelain tiles, decent screen | — | ×1 |
| High end Designer brassware, large-format porcelain, stone resin | — | ×1.55 |
Extras
| Option | Cost | Effect on total |
|---|---|---|
| Full tanking to the wet areas Do not let anyone talk you out of this | £400–£1,100 | Added |
| Wet room — floor former and drainage into the joists | £1,600–£4,500 | Added |
| Electric underfloor heating | £500–£1,400 | Added |
| Proper extractor ducted to outside The single best defence against black mould | £250–£700 | Added |
| Shower pump or mains booster | £600–£1,600 | Added |
| Macerator / pumped waste (no gravity fall) | £700–£1,800 | Added |
| Moving or renewing the soil pipe | £900–£3,200 | Added |
| Strengthening or notching joists for a new bathroom | £800–£2,600 | Added |
| Replacing the bathroom window | £600–£1,600 | Added |
| Re-plastering / boarding out | £600–£1,800 | Added |
Where is the property?
Labour rates and builder demand vary more than materials do.
| Option | Cost | Effect on total |
|---|---|---|
| London | — | ×1.25 |
| South East | — | ×1.12 |
| South West | — | ×1.03 |
| East of England | — | ×1.03 |
| Midlands | — | ×0.97 |
| North of England | — | ×0.92 |
| Wales | — | ×0.92 |
| Scotland | — | ×0.95 |
| Northern Ireland | — | ×0.85 |
Applied to every total
| Item | Amount |
|---|---|
| Contingency | 10% of build cost |
| VAT | Included at 20% unless stated |
Why bathrooms cost more per square metre than anything else
A 4m² bathroom needs a plumber, an electrician, a tiler, a plasterer, a carpenter and a decorator, most of whom cannot work at the same time as each other. You are paying for six mobilisations, not for floor area. This is also why the price gap between a small bathroom and a large one is smaller than people expect.
The three things worth paying for
Tanking
A liquid or sheet membrane over the shower zone and floor, taken up the walls and into the corners with reinforcing tape. Non-negotiable in a wet room, strongly advised in any shower enclosure. Skipping it is the single most common cause of the leak that appears three years later through the kitchen ceiling.
Extraction
A fan sized for the room, ducted in rigid pipe to an outside terminal, with an overrun timer. Condensation and black mould are almost always a ventilation problem wearing a damp costume.
The tray or bath install
Trays must be fully bedded, not sat on four corners; baths must be properly supported and filled with water before the silicone goes on. Both are twenty minutes of care that decide whether the seal lasts.
What surveyors flag in bathrooms
- Staining on the ceiling below — historic or live, and it matters which.
- Springy or blackened floor — long-term leak into the joists.
- No extractor, or one venting into the loft — a mould factory.
- Old-style pull-cord switching or exposed sockets — Part P concerns.
- Macerator on the only WC — mortgage lenders occasionally query it.
If your survey mentions any of these, the fix is usually far cheaper than the wording suggests — but only once someone has looked behind the panel rather than at the report.
Where to save
Keep the soil pipe where it is. Choose a good ceramic suite over a designer one — the shape of a toilet has not improved much. Spend the saving on brassware, which you touch every day, and on the parts you cannot see.
Frequently asked questions
How much does a new bathroom cost in the UK?
A straight replacement in the same layout with mid-range fittings typically costs £7,000–£13,000 including tiling, tanking and making good. Moving the suite around adds £3,000–£6,000. Creating a brand new bathroom or en-suite where there was no plumbing usually starts around £10,000.
What is tanking and do I really need it?
Tanking is a waterproof membrane applied to walls and floors before tiling. Tiles and grout are not waterproof — the membrane behind them is what keeps water out of the structure. It costs a few hundred pounds and is the difference between a bathroom that lasts fifteen years and a ceiling collapse below in five.
How long does a bathroom take?
Ten to fifteen working days for a straightforward replacement, assuming everything is on site before day one. Longer if walls need re-boarding, if the floor has to come up, or if a single missing part stops second fix — which happens constantly.
Do I need building regulations approval for a bathroom?
Electrical work in a bathroom is notifiable under Part P and must be certified. New or altered drainage, structural alterations to joists, and ventilation to a room without an openable window all fall under building regulations too. A like-for-like swap with no electrical or drainage change generally does not.
Why does my extractor not stop the black mould?
Usually because it is undersized, recirculating rather than ducted outside, ducted through crushed flexible hose, or set to run for too short a time. A properly sized fan ducted in rigid pipe to an external terminal, with a fifteen-minute overrun, removes moisture rather than moving it around. It is the cheapest fix in the house.