How to price a bathroom (plumbing)

The mistake most people make is jumping straight to the shower and toilet, because that is what the customer can see. But the underlying construction is what costs time, and it is also where the responsibility sits. Price it before anything else.

A plasterboard ceiling in a wet room is built in 2 layers to carry lighting and extraction and keep a flat surface, and walls and floor need a substrate that can carry the waterproofing. The pipework is usually hidden in a pipe box, and the box itself must be a line item: battening, board, filling and painting cost real hours that disappear if you only think about the pipes inside.

• Plasterboard ceiling in 2 layers with battening and moisture-resistant board
• Pipe box around the soil stack and visible pipes: built, filled and painted
• Substrate on floor and wet walls that can carry the membrane
• Packing and fall in the floor build-up towards the drain

The water installation is priced on metres of pipe plus fittings and fixings. In modern bathrooms water pipes are run as pipe-in-pipe, so a leaking pipe can be pulled and replaced without breaking up the tiles, and this is also a requirement in hidden, inaccessible runs. Choosing copper instead of PEX changes both the material price and the installation time, because press fittings and soldering do not take the same amount of time.

Price cold and hot separately in metres, add the manifold cabinet for pipe-in-pipe, and remember fall on the drain line. Waste water needs fall, typically around 20 per mille (20 mm per metre) for the smaller dimensions, otherwise the water sits still. Fall is not a detail, it is a line item that decides whether the bathroom works.

Sanitary ware is the visible units, but the price sits in the hidden work. A Geberit concealed cistern requires a mounting frame in the wall, reinforcement behind the tile and building-in, so it weighs more in hours than the toilet itself. Set the cistern, frame and installation as separate lines, not as one figure.

The shower drain, for example a unidrain linear channel drain, requires the floor to have correct fall towards the channel, so the water runs away and does not stand on the tiles. Fall to the drain is a trade line item: build-up, levelling and check-measurement. Price it so you are covered if the floor has to be built up to hit the fall.

• Toilet with concealed cistern: cistern + frame + building-in as separate lines
• Shower drain (unidrain or point drain) with connection
• Basin and taps with connection and pressure test
• Fall to the drain: build-up and check as a standalone line item

The membrane is what makes the bathroom a wet room. It must cover the entire wet zone: the floor and the lower parts of the walls in and around the shower area, with cuffs at penetrations and pipe passages. The membrane is priced per m², and consumption follows the manufacturer's datasheet: two applications with a specific number of grams or litres per m², plus reinforcement tape in all corners and joints.

Do not guess the consumption. Read the datasheet for the system you use, multiply by the actual wet-zone area, and add waste and tape on top. This is where people either buy too little material or set aside too few hours for the double application with drying time in between.

Work on the water and drainage installation requires a licensed plumbing installer, and gas work requires a separate licence. This is not just a formality, it is responsibility and documentation. Therefore the licence-requiring work should always stand as its own lines in the quote, separated from demolition, tiling and painting.

The benefit is twofold: the customer can see exactly what the licensed installer vouches for, and you have backing if questions about responsibility or an insurance case come up later. Never mix licensed installation work with the non-licensed work into one jumble of a line.

A bathroom should be divided into clear sections, so the customer can see what the money goes to, and so you can price each part on its own:

• Demolition and disposal: old fixtures, tiles, floor, skip
• Plumbing installation: water and drainage pipes, connections, licensed work
• Wet room: membrane, fall to the drain, build-up of floor and wet walls
• Fitting: sanitary ware, taps, concealed cistern, final test

Finally you add the labour hours. Price hours per section instead of one lump figure, so you can see where the time actually goes, and so a change in one section does not topple the whole price. Hourly rate times actual hours per part, plus materials per datasheet, gives a quote you can stand behind.

Calco works out the quantities for you: metres of pipe, m² of membrane per the manufacturer's datasheet, fall to the drain and labour hours, and knows the licensing requirements, so the high-responsibility work lands on its own line. You get a divided quote with real prices, instead of a round estimate you hope holds. See how Calco builds a plumbing quote at /tilbud-vvs.