Bathroom Refit Cost Calculator: Estimate by Works Type

How the calculation works

Bathroom refit cost: what drives the budget

A bathroom refit is one of the jobs that changes a home the most, and one of the easiest to push past its original budget. The difficulty lies in what sits behind the tiles: ageing pipework, damaged plaster, old leaks that were never fully dealt with. Many UK homes are decades old, so these surprises are common rather than unusual. This calculator gives a structured starting estimate, built from the floor area, the type of works, the grade of finishes and the choice of sanitaryware and taps, so you can see which decisions move the total most.

The type of works defines the budget

The single biggest factor in the total is the type of refit.

A cosmetic refit leaves the tiles and the pipework untouched. The focus is visual: painting the walls with a paint suited to humid rooms, replacing accessories such as the towel rail, toilet roll holder, mirror and lighting, and fitting a new tap and, sometimes, a new toilet pan. It is the lowest-cost option and suits a bathroom that is fairly recent but looks tired. Select this type in the calculator to get the matching estimate.

A mid-range refit is the most common choice for people who say they are doing up the bathroom. It includes removing all the existing wall and floor tiles, renewing the waterproofing, fitting new tiles, and replacing the sanitaryware and taps. The cost of this segment depends mostly on the floor area and the materials you choose.

A full refit covers everything in a mid-range refit plus structural changes. That can mean moving the toilet, basin or shower to a new position, which requires new supply and waste runs, reinforcing the hot water supply, changing the electrical circuit to add an extractor fan, a heated towel rail or an electric shower, and in some cases removing part of a wall. This is the most expensive option. The labour and materials for the structural work alone usually exceed those of a mid-range refit of the same room, before any sanitaryware is counted.

Floor area matters, but less than you might think

Refit costs do not scale in direct proportion to area. The largest single block is installation labour, and a plumber spends roughly the same time connecting a toilet in a 3 m² room as in a 6 m² one. What grows with area is the tiling, both the material and the time needed to set it out and fix it.

In a 5 m² bathroom, the wall area to be tiled up to 2.2 m high (about 7 ft 3 in) is roughly 15 to 18 m². The exact figure depends on the number and size of doors, windows and recesses. Measure the floor area wall to wall on the inside, and enter that figure in the calculator.

Tile choice changes the cost too. A standard ceramic wall tile is considerably cheaper to buy and fix than large-format porcelain, such as 600 × 1200 mm tiles, which need a flatter substrate, more careful setting out and specialist cutting. In a small room, large-format tiles can add substantially to the material cost for the same area, so treat the grade of finish as a separate decision from the size of the room.

Sanitaryware and tapware grades

Budget suites typically combine a close-coupled toilet, a pedestal basin and an acrylic shower tray. Mid-range suites, a common choice for standard refits, add better-finished ceramics, soft-close seats and a wider choice of basin and tray sizes. Premium suites include wall-hung pans with concealed cisterns, inset or countertop basins, and glass shower trays with a concealed waste, usually paired with a thermostatic shower valve and a rain head. Tapware follows the same pattern, from basic mixer taps to thermostatic valves.

Fittings connected to the mains water supply should meet the requirements of the Water Supply (Water Fittings) Regulations 1999 in England and Wales. The rules for the rest of the UK differ, so check them with the water supplier before you buy. Check the technical data sheet for each product, because guarantee periods differ and are not a reliable guide to quality on their own.

Waterproofing: the item most often underestimated

Waterproofing is the most critical item and the one most often left out of early budgets. Approved Document C of the Building Regulations deals with protection against moisture, and BS 5385-1 sets out good practice for tiling in wet areas. In practice, tradespeople usually apply a liquid-applied waterproof membrane in two coats to the floor and to the wall areas around the shower and bath, following the product's data sheet for coverage and drying times. A defect rarely shows the day after the work. It often appears a year or two later, when water seeps through to the ceiling of the room below. Waterproofing belongs in the budget from the start, not as an afterthought.

Smaller finishing items are easy to forget. Trims, such as transition profiles between the bathroom floor and the hallway, are needed where floors meet. Sealant is needed at movement joints where walls meet the floor, in internal corners, and around the basin and shower tray. Each item is small, but they add up quickly if they are not in the budget.

Common mistakes

The most frequent errors are leaving waterproofing out of the quote or accepting a quote that does not mention it, forgetting trims, sealant, the extractor fan and the tile cuts, and choosing sanitaryware before checking the room dimensions and the position of the existing pipework. Allow extra tiles for cuts and breakages, and buy them from a single batch so the colour is consistent. Finally, do not treat the estimate as a fixed price. Hidden defects are the usual reason a refit overruns, so keep a margin for them.

When to bring in a professional

For cosmetic refits and for mid-range refits that do not change the pipework, a competent plumber or tiler with verifiable references and a record of similar work is usually enough. Good tradespeople often book several weeks ahead, so plan the timetable early.

For work that moves pipework across the floor (which usually means lifting floorboards or a screed), alters the soil stack, or opens up masonry walls, bring in an architect or structural engineer to coordinate the job. Coordination is easier to justify when three or four trades must work in sequence in a small space.

Electrical work in a bathroom is subject to Part P of the Building Regulations in England and Wales. It must be carried out by someone registered with a competent person scheme, or notified to building control. Ask for an electrical installation certificate at the end of the job. Any gas appliance work, such as moving a boiler or fitting a gas heater, must be carried out by an engineer on the statutory gas registration scheme.

If you live in a flat, check the lease. Many leases require consent from the freeholder or managing agent before you change pipework or drainage that is shared with other flats.

Planning and building control

Whether a refit needs planning permission or Building Regulations approval depends on what the work changes, not only on whether the fittings are replaced in the same place. If the property is listed, works that affect its character may need listed building consent under the Planning (Listed Buildings and Conservation Areas) Act 1990, so check with your local planning authority before you start. New electrical circuits in a bathroom, and new or altered drainage, normally need to comply with Part P and with Approved Document H (drainage and waste disposal). Ask your local building control team to confirm what needs approval before you start. In Scotland, the Building (Scotland) Regulations 2004 apply instead, and the local authority building standards team can confirm what needs approval.

When not to rely on this estimate

The calculator is not suited to listed buildings with unusual construction, to bathrooms with known damp, timber decay or structural movement, or to projects with major structural work. In those cases, get a survey before you set a budget. The estimate also assumes standard access and a straightforward layout. A room on an upper floor with restricted access, or one where all materials must be carried up stairs, will cost more than the figure suggests.