The order of a bathroom renovation in one paragraph
A bathroom renovation runs in this order: survey, decisions on fittings and layout, strip-out, first-fix services, waterproofing with a leak test, screed with falls, tiling, installing sanitaryware and furniture, handover. The most expensive mistakes happen in the stages later hidden behind tiles: you cannot see them, and fixing them means breaking new finishes.
Below I go through each stage and what to check at it. Tile choice and styling are left out here; they have their own articles.
Survey: what to find out before designing
The first thing we look at is the soil stack. In Eixample buildings it is usually shared, cast iron or old plastic, running up a corner of the bathroom or kitchen. If it is in poor condition, the section inside the flat cannot be replaced without involving the comunidad de propietarios, so you need to know before pricing.
Next: what the pipework inside the flat is made of, where the waste runs and at what fall, and what floor structure lies underneath. On timber joists or Catalan vaults you often cannot drop the floor for a level-access shower, and the design changes while it is still on paper. We check the electrics: dedicated circuit, earthing and RCD protection. And ventilation: whether there is a window, and where an extractor can discharge.
Decisions to make before strip-out
Level-access shower or tray, bath or no bath, wall-hung WC on a concealed frame, concealed shower valves, a niche in the shower wall, underfloor heating, a backlit mirror, a socket for the hairdryer by the basin: each of these fixes where pipes and cables will run. Change your mind after first fix and what has been installed gets opened up again.
So by the time strip-out starts you should have specific sanitaryware models chosen, with technical data sheets, not photos from the internet. A concealed cistern from one maker and a flush plate from another, a valve with an unusual concealed body: these mismatches come to light on exactly the day the tiler arrives.
Strip-out and first fix
Once stripped, the real state of walls and floor shows, and surprises are common: a decayed section of joist, an old lead pipe, unprotected wiring. A good contractor shows you straight away and proposes a priced solution before carrying on.
With the pipes in, they are pressure-tested and the whole layout is photographed with dimensions for reference. Those photos will matter in ten years when you want to put up a shelf without drilling into a pipe. Ask the contractor for them and keep them.
Waterproofing: the stage you cannot rush
Waterproofing covers the entire bathroom floor and, in the shower zone, the walls as well, carried well up. Corners, the junction with the drain and pipe penetrations are reinforced with tapes and collars, because that is where leaks usually start. Before tiling, a flood test is done: the floor is filled with water and left for a period.
If a contractor wants to tile straight after applying the membrane, without waiting for it to cure or testing it, they are saving their days at the cost of your risk. A leak into the flat below in an old building means repairing the neighbour's ceiling, a conversation with the comunidad and lifting your brand-new floor.
Tiling, sanitaryware and finishing
Agree the tile setting-out before work starts: where the cuts fall and how the joints line up with the niche, the drain and the mirror. Large-format tiles need a very flat substrate and an accurate fall to the drain. The fall is checked with water, not by eye: no water should sit in any corner of the shower.
Sanitaryware and furniture go in after grouting. Access to the WC frame and to the concealed valve bodies must remain, even if disguised. The extractor is wired with a timer or humidity sensor; damp in bathrooms has its own article.
Handover: what to check with your own hands
Run water into the shower and watch where it goes. Turn on every tap at once and check the pressure and how long hot water takes to arrive. Switch on the extractor and hold a sheet of paper to it. Check the silicone around the bath and tray, the cabinet doors and gaps. Ask for the photos of concealed services and the data sheets for the installed fittings.
The Urgel flat in the Eixample has two bathrooms, and each was handed over separately against a list like this. Record snags in writing with a date for the fix: that is how a job actually finishes instead of dragging on with small touch-ups.