First fix is the stage of a job where cabling, pipework and containment go in before the walls and ceilings are closed up. It looks unglamorous — bare cable and pipe against studwork — but almost every socket, switch, tap and outlet position gets fixed at this point, and changing your mind afterwards means opening up finished walls.
Understanding the sequence helps explain why this stage takes real time and real coordination between trades, rather than being something to rush through to get to the visible finishes.
Walking positions on site before anything is fixed
Drawings show approximate positions for sockets, switches and outlets, but the final call gets made standing in the actual room, with furniture heights, door swings and worktop lines in mind. A socket position that looks fine on a plan can sit awkwardly behind a planned fridge or above a worktop upstand once it's physically laid out.
This is why a competent electrician or plumber will walk the room with the client or the designer before fixing anything, marking positions directly onto the studwork or wall rather than working purely from a drawing.
Installing before boarding
Cabling and pipework go in while the studwork or wall is still open, run through joists and studs, clipped or strapped in place, and terminated at back boxes and stub-outs ready for the second fix trades to connect into later.
This has to happen in the right order relative to other trades — insulation, sound-proofing and boarding all follow first fix, and getting the sequence wrong means opening things back up.
Recording what's inside the wall
Once the wall is closed, nobody can see what's behind it. Photographing runs before they're covered — and keeping those photographs somewhere the client can access later — means a future job, whether that's hanging a shelf or finding a leak, doesn't start with guesswork and a drill.
- Photographs of cable and pipe runs before boarding
- Measurements from a fixed reference point, such as a corner or floor line
- A simple sketch marking anything unusual, like a run that isn't straight
Testing before plastering
Electrical circuits get tested and plumbing runs get pressure tested before the wall is closed up, because faults found after plastering mean cutting back into a finished surface. This testing stage is a genuine checkpoint in the programme, not a formality to skip past.
A certificate or test record from this stage is worth keeping with the rest of the project paperwork, since it's evidence the work was checked at the point it was actually accessible.
Where first fix sits in the wider programme
First fix generally follows any structural work and precedes insulation, plasterboard and plastering. Getting this sequence wrong — for example plastering before an omitted circuit is spotted — is one of the more expensive mistakes to unpick on a job, because it means undoing finished work rather than adjusting something still open.
A programme that shows first fix as a distinct, protected stage, rather than squeezed between other trades, is one that's been thought through properly.
Common questions
Why does the electrician need to visit before fixing anything?+
Socket, switch and outlet positions are best confirmed physically in the room, against furniture, worktops and door swings, rather than relying on a plan drawing alone. This avoids awkward positions that only become obvious once the room is laid out for real.
What happens if I want to move a socket after first fix?+
It's possible, but it usually means cutting back into boarded or plastered wall to move the cable, which costs more and takes longer than agreeing the position before boarding goes up.
Should I ask for photographs of the pipework and wiring?+
Yes — ask for these to be taken before the wall is closed and kept with your other project paperwork. They're genuinely useful for any future work on the house.
Ask us to walk first fix positions with you before we start
We agree every socket, switch and outlet position on site before anything is buried in the wall.