Complete bathroom renovation, stripped back to the walls

A complete renovation makes sense when the problems are behind the surface: tiles that sound hollow, a floor that flexes near the toilet, old lead or galvanised pipework, a leak that has stained the ceiling below, or a layout that wastes space. It also makes sense if you want a different arrangement, such as swapping the bath and the shower, adding a second basin or turning the room into a wet room.

It is usually not worth it if the suite is sound and the tiles are firmly bonded. In that case, replacing selected items is a partial refit and costs a good deal less. A useful test is to ask the fitter what they would find if they took one wall of tiles off. If the honest answer is that they do not know, a full strip-out is the only way to find out.

Most full refits follow the same sequence: strip-out and removal of waste, repairs to joists and floorboards, first fix of plumbing and wiring while walls are open, boarding or plastering, waterproofing in the wet areas, tiling or panels, flooring, then second fix of the suite, taps, lights and fan, and finally sealing and decoration. Each stage has to be finished before the next can start, and some need drying time.

Because every surface is renewed, this is the moment to decide where pipes run, whether a concealed cistern or wall-hung toilet needs a frame, where towel rails and shaver sockets go, and whether you want electric underfloor heating. Changing any of those after tiling means breaking tiles.

• a floor plan showing each item and every change to the waste routes
• how the floor will be repaired or overboarded before tiling
• which walls are tanked or fitted with a waterproof backer board
• the fan position, duct route and where it vents outside
• which electrical work is notifiable and who certifies it
• how many days the house will be without a working toilet

A full refit often brings heavier finishes than the room was built for: a cast-iron or stone resin bath, large porcelain tiles, a stone basin. The Planning Portal warns that a new bath on a timber floor can overload the joists once it is full of water and in use, and that a structural engineer or surveyor may need to assess the floor. If strengthening is needed, they produce the paperwork a building control body will want before work starts.

Timber floors also move, and large tiles crack if laid on boards that flex. Ask the fitter how the floor will be stiffened and what board goes under the tiles.

Approved Document F sets a minimum intermittent extract rate of 15 litres per second for a bathroom. On a refurbishment, an existing fan has to be kept or replaced; if there was none, you are not obliged to add one unless the work makes the room less compliant than before. On a full refit it is almost always worth fitting a fan that meets the rate and ducting it to the outside rather than into the loft.

Under Part P in England, the space within 0.6 metres of the edge of a bath or shower tray, up to a height of 2.25 metres, is a special location. Any addition or alteration to circuits within it is notifiable, as is any new circuit anywhere, for example for an electric shower. A full refit nearly always includes some of this work, so the quote should say whether it is self-certified by a registered electrician or notified to Building Control.

Price is driven less by the suite than by labour and the unknowns: the size of the room, how much tiling there is, whether waste pipes move, the state of the floor and walls once the old tiles are off, and how much electrical work is involved. Tiling floor to ceiling in a small room with many cuts can take longer than tiling a larger, simpler room.

Ask for a price that separates the fixed work from provisional sums for things nobody can see yet, such as replacing rotten joists, and ask how those sums will be agreed if they are needed. A quote that is only a single figure makes it hard to compare and easy to argue about later.

Describe the room and what you want to change, then confirm your phone number and email address. Bathroom companies near you see the job without your contact details, and one company can buy it; after that it is taken off the list and not offered to anyone else. We email you that company's name, address and phone number before it sees your details. There is no guarantee a company takes it up, and it is withdrawn after 21 days if not. Offrano only checks that the buyer is a registered business, so ask to see finished full refits and the electrician's registration before you agree a price.