In short: the sequence and the reason
Services go in after the structure and partitions and before plaster, plasterboard, screed and tiling. Within that window one simple rule applies: first whatever works by gravity and needs a fall, then whatever takes up a lot of space, and last whatever can bend. Once the walls are closed, any change of route means opening up finished surfaces.
This holds for a new-build house and for a full flat renovation alike. Only the scale differs: a house has more and longer service runs; a flat has less room and more constraints from the neighbours.
The order in which services go in
Drainage goes first. The pipes need a fall, they are large in diameter and cannot be shifted a couple of centimetres without losing it. Next come ventilation and air-conditioning ducts: they are the bulkiest and they set the height of the suspended ceilings. Third, water supply, heating and underfloor heating manifolds. Last, electrics and data: a cable in flexible conduit easily routes around whatever is already there.
Break the order and the electrician takes the best route under the ceiling, and the duct no longer fits. That leaves two options: drop the ceiling below the design height or redo the wiring. Underfloor heating always goes down before the screed, and its manifold must stay accessible.
Setting out before the first pipe
Installation starts with setting out on walls and floors. Partitions, door openings, furniture, the kitchen, appliances, bedside wall lights, the TV: everything must be decided and drawn. You cannot run water to the kitchen sink if the kitchen design does not exist yet, or place sockets by the bed if nobody knows which wall it will stand against.
So by the time services start, the kitchen, bathrooms and built-in furniture are already designed and the appliance dimensions confirmed. On site every point is marked directly on the wall, with its height from the finished floor. It is slower than "we'll sort it out as we go", but nobody has to chase into fresh plaster later.
A real case: concealed doors and heat recovery
In the 250 m² child psychology centre in the Eixample, which we built out between January and June 2026, there were 24 concealed doors and a climate system with heat recovery. Both depend entirely on the stage before the walls are closed.
A concealed door frame is fitted flush with the wall before finishing, and no switch or socket can be added next to it at the last minute: it would end up where the door leaf swings. Heat-recovery ducts are bulky and have to run beneath the slab before the suspended ceiling is closed. On a job like that, duct routes, electrics and the position of every door are resolved together on one drawing in advance, not on site.
What the owner should check before closing
Before the walls are closed we walk the site with the client, drawings in hand. Check this list. Sockets by the bed, the kitchen worktop, the island, the TV and the desk, at the right height. Switches on the handle side of the door, not behind the leaf. Light points over the table and the island, not wherever suited the electrician. A water supply for the fridge and coffee machine, if needed.
Separately, blocking inside the walls for heavy items: the TV, wall cabinets, shelves, curtain tracks. And spare empty conduits: to the TV, to the garden, to the roof for future solar panels. An empty conduit costs very little now; a new cable route through a finished house is a project of its own.
Testing and photo records
Before closing, water and heating pipework is pressure-tested, and drainage is tested with water and checked for falls. The result is recorded: a leak found now costs one fitting; found a year later, it costs the neighbour's ceiling or your own parquet.
Every wall is photographed with a tape measure in the frame, so that years later you can see where a pipe runs and where not to drill. Those photos and the updated service drawings stay with the owner along with the rest of the project documentation. In a house this is especially useful: there are many runs, and after a few years nobody remembers where the cable to the pool pump goes.
What a change costs after closing
Moving a socket before plastering is half an hour of an electrician's time. Moving it after painting means opening the wall, running a new route, plastering, skimming and repainting the whole wall so there is no patch. If the wall is tiled, add the removal and the hunt for tiles from the same batch, which may no longer exist.
That is why changes are best made during the pre-closing check and put in writing. It is the one moment in a build when changing your mind costs almost nothing.