First Fix vs Second Fix: What Happens at Each Stage of a Build
In short
First fix is the stage where services and structure that will be hidden are installed: pipework, cables, back boxes, studwork and door linings, before plastering. Second fix comes after plastering and covers everything visible: sockets, switches, sanitaryware, radiators, doors, skirting and kitchen units.
First fix and second fix are the two main installation stages in any renovation, and they sit either side of plastering. First fix is everything that will end up hidden inside walls, floors and ceilings. Second fix is everything you will see, touch and use once the walls are finished. Understanding the difference helps you know where your project is, when decisions are needed and why the first stage matters so much to the final result.
What happens at first fix
- Plumbing: supply and waste pipes run to every tap, shower, bath, WC and appliance, pressure tested before they are covered.
- Heating: pipework to radiators, underfloor heating loops and manifolds.
- Electrics: cables run to every socket, switch, light, extractor and appliance, with back boxes set in the walls.
- Carpentry: stud walls, noggins for wall hung fittings and heavy units, door linings and window boards.
- Ventilation and data: ducting for extractors, and cabling for data, speakers or security.
In bathrooms, waterproofing and tanking follow first fix. In kitchens, every service position must match the final kitchen layout, because a tap or a hob cable in the wrong place is expensive to move once the walls are plastered.
What happens at second fix
- Plumbing: sanitaryware, brassware, radiators and appliance connections.
- Electrics: sockets, switches, light fittings, extractors and the final testing and certification.
- Carpentry: doors, skirting, architrave, fitted joinery and kitchen units.
- Finishes: worktops, splashbacks, tiling trims and ironmongery.
Why first fix decides the finish
The quality you see at second fix is set at first fix. A shower valve set at the wrong depth will never sit flush with the tiles. A back box out of level will never give a straight socket. A pendant above a kitchen island must be positioned before the ceiling is boarded. That is why final layouts, fitting choices and lighting plans should be fixed before first fix starts, and why a careful first fix check, with photographs of every pipe and cable run, is worth its weight.
How it fits into the programme
A typical sequence is: strip out, structural work, first fix, inspections, plastering and screeding, drying time, tiling and decorating preparation, second fix, decoration, then snagging and handover. Your schedule of works should show first and second fix as separate stages, so payments and progress are easy to track.
How we handle first and second fix on London’s Prestige projects
Before first fix, we confirm every fitting, socket and light position with you against the final drawings. Our team then photographs the services in every wall before plastering, so there is a record for the future, and checks setting out against the chosen fittings before anything is closed in. The aligned joinery and services on our Staveley Road kitchen in Chiswick show what that care produces. See our kitchen renovation service, or arrange a site visit to plan your project with us.
Common questions
Can I change my mind after first fix?
Yes, but it costs more the later it happens. Moving a socket or tap before plastering is quick; moving it after tiling means cutting out finished work. Fixing layouts before first fix saves time and money.
Is there an inspection between first and second fix?
Often. Building control may inspect certain work, plumbing is pressure tested, and your contractor should check every position against the drawings before plastering begins.
What comes between first fix and second fix?
Plastering, screeding and drying, followed by tiling and preparation for decoration. Drying time is important, especially for screeds under tiles or timber floors.