Bathroom fittings checklist for a renovation

In a bathroom the fittings are decided by the pipes, and the pipes are set before the tiles go on. Most expensive mistakes come from choosing a toilet, shower or heater after the rough-in is done. This checklist runs through the fittings in the order the decisions have to be made, so you can give the contractor the right dimensions at the right time.

Water pressure and heater type

Start with the heater, because it decides which taps and showers are possible. A storage heater (a tank of typically 15 to 50 litres, usually above the false ceiling or on the wall) heats water that is then mixed at the tap, so it works with mixer taps, rain showers and more than one outlet. An instant heater heats water as it flows through a single unit at the shower; it needs less space and no waiting, but the flow is lower and it only serves that one point, so a rain shower on an instant heater will feel weak.

Check the pressure before choosing a large rain shower. Flats on upper floors fed by the roof tank, and older blocks, can have modest pressure; a 250 or 300 mm rain shower head needs a good flow to feel like rain rather than a drip. A rough test is to time how long a 10-litre pail takes to fill from the existing shower: if it fills in well under a minute the flow is comfortable; if it takes a couple of minutes or more, choose a smaller head or an air-injection model that makes the most of low flow, and compare the flow with the minimum stated in the shower's specification.

• Single-lever mixer: one handle controls flow and temperature; the everyday choice for basins and showers on a storage heater.
• Thermostatic mixer: holds the set temperature even when someone flushes elsewhere; worth it for a family bathroom with children or elderly parents.
• Single cold tap or an instant heater with its own control: for a service bathroom or a bathroom without a hot-water point.

Mixer taps and rain showers

A rain shower hangs either from a ceiling-mounted arm, which needs the pipe run above a false ceiling and the arm's position fixed before the ceiling is closed, or from a wall arm that comes out of the tiled wall, typically around 1.9 to 2.1 m from the floor. The wall arm is the simpler retrofit; the ceiling arm gives a cleaner look and lets the head sit over the centre of the shower area. Either way, pair it with a hand shower on a slide bar for rinsing the floor and washing children, and route it through a diverter on the mixer.

Finishes are chrome, brushed nickel, matte black and gunmetal. Chrome is the hardest-wearing and easiest to match later; coloured finishes look good when every fitting in the room matches, so buy the mixer, shower, towel rack and accessories in the same finish from the same range if you can. Check that spare parts (cartridges, aerators) are available for the model you choose.

Smart toilets

A smart toilet or a bidet seat needs three things in place at the rough-in stage. First, a power point: a socket within reach of the toilet's cable, on the side the cable exits, on a protected circuit and in a splash-protected position, installed by a licensed electrical worker. Second, the rough-in: the distance from the finished wall to the centre of the waste outlet. It varies between blocks and developments (305 mm is common, and other sizes exist), so measure it rather than assume; the toilet must match it or the contractor has to move the pipe. Third, the water inlet: the toilet's stop valve is on the left or the right of the bowl, from the wall or the floor, and the seat needs a T-piece from that inlet.

Decide between a bidet seat and a full unit. A bidet seat fits on an existing standard bowl, keeps the tank and costs a fraction of the price; it is the right answer for an existing bathroom. A full smart toilet is a one-piece unit with the wash, dryer, heated seat and often a tankless flush that needs reliable water pressure to flush well; check the minimum pressure in the specification and confirm the trap type (S-trap for a floor outlet, P-trap for a wall outlet) matches the flat.

Towel racks, shelves and accessories

Accessories go in last but the plan for them should exist early, because every fixing on a tiled wall is a drilled hole. Porcelain and homogeneous tiles need a diamond bit and a slow drill; avoid drilling into grout lines, which crumble, and keep well away from the pipe runs the contractor marked during rough-in. Ask the contractor to photograph the pipework before the tiles go on.

Typical heights are a towel bar at about 1.2 m from the floor, hooks at around 1.6 to 1.7 m, a shelf over the basin at eye level and a toilet-roll holder at about 650 mm from the floor beside the bowl; adjust them to the people who use the room. Adhesive and suction fixings avoid drilling and are fine for light items such as a soap dish on a smooth tile, but a towel rack or a shelf that will carry weight should be screwed into plugs. Choose the same finish as the taps so the room reads as one set.

Order of work with the contractor

The sequence in most bathroom renovations is hacking, then plumbing and electrical rough-in, then waterproofing and the required curing time, then tiling and the false ceiling, and only then the fixing of sanitary ware and accessories. The toilet, the mixer body, the shower arm and the heater all set pipe positions, so they must be chosen, or at least their dimensions confirmed, before the rough-in. Accessories and the basin tap can be chosen later, as long as the finish is decided.

Hand the contractor one sheet with the model names, the rough-in distance, the heater type and position, the socket positions, the shower arm height and the accessory layout. It takes an hour to write and avoids the second visit from the plumber.