What a bathroom refit actually involves

The expensive mistakes on a bathroom are nearly all made at the shopping stage, weeks before anyone turns up. A bath that is 1700mm long will not go into a 1690mm gap no matter how good the fitter is. A shower tray that needs a 90mm build-up will not sit flush on a solid concrete floor without something giving. And a thermostatic shower valve rated for a certain pressure will dribble on a system that cannot supply it.

• Measure the room properly — wall to wall, both ends, because old houses are rarely square.
• Check your water pressure and what kind of system you have before choosing a shower.
• Know your floor: suspended timber and solid concrete behave completely differently.
• Decide on the layout before the suite, not after. Moving a soil pipe is the single biggest cost swing in a bathroom.
• Send the spec past your fitter before you click buy. It takes five minutes and saves a fortnight.

Day one is loud and ugly. The suite comes out, the tiles come off, and quite often the plasterboard behind them comes off with them. This is also the point at which the house tells you the truth: rotten floorboards under the old bath, a previous fitter's leak that nobody ever found, pipework buried in a wall with no isolation on it, or a stud wall that turns out to be holding something up.

• Expect the odd surprise — every honest fitter builds a bit of slack in for it.
• Anything rotten or wet gets cut out now, not tiled over.
• Old suite, tiles and rubble should be taken away, not stacked in the garden.
• This is the only time you will see the bones of the room. Look at them.

With the room stripped, the pipework is reset for where things are actually going: bath, shower, basin, WC, towel rail. Waste runs get the right falls, hot and cold get isolated so a future tap change does not mean draining the house, and everything is pressure-tested before a single board goes back on. Any cabling for lighting, shaver points, extractor or underfloor heating is run at the same time.

• Every joint tested before it is covered up.
• Isolation valves fitted where a future you will thank us for them.
• Extractor ducted to outside, not into a loft void.
• Electrical work that needs certifying is done by someone who can certify it.

Walls get boarded flat and floors get levelled, because tiles are rigid and will telegraph every dip and bow underneath them. Wet areas — the shower enclosure, around the bath, any wall taking a rainfall head — are then made properly watertight before tiling. Grout is not waterproof, and neither is standard plasterboard. This stage is invisible in the finished room and is the one that decides whether it is still sound in ten years.

• Flat walls are a prerequisite for large-format tile, not a luxury.
• Movement is designed for — floors flex, and rigid finishes need to cope with it.
• Underfloor heating, if it is going in, is laid and tested before it is covered.
• Waterproofing goes behind the tile, because the tile is not the waterproof layer.

Before any adhesive is mixed, the room is set out dry. Centre lines are found, cuts are balanced so they fall evenly at both ends of a wall, the bond and direction are agreed, and the tile is checked across boxes for shade variation. It is the least glamorous hour of the whole job and it is the one you will notice every morning for the next fifteen years, because a badly set-out wall puts a sliver of tile in the corner you look at while you brush your teeth.

• Cuts balanced end to end, never one full tile and one sliver.
• Tile shade checked across boxes before fixing — batches vary.
• Order 10–15% over on plain layouts and more on herringbone or diagonal, because the cuts eat tile.
• Internal corners siliconed rather than grouted, so they can move without cracking.

Suite, screen, taps, shower, radiator and accessories go on. Everything is run, filled, drained and checked for leaks under real use rather than a quick turn of the tap. Silicone goes in last, and it needs time to cure before the bath is filled or the shower is used — which is the one instruction people most often ignore. Then the floor is cleaned, the protection comes up, and the room is yours.

• Everything run and checked before we leave, not on your first morning.
• Silicone needs curing time — usually around 24 hours before heavy use.
• Snagging done by us before you find it.
• Spare tiles left with you, labelled. One day you will want them.