Once the plasterboard is on, every question costs demolition to answer. First fix is the last moment checking is free: walk the site, tick the list, and photograph every wall that is about to disappear. Your ticks stay on this device.
The end-of-build version of this page is the snagging checklist: what to check at handover, room by room. And if something is found that was not in the quote, it belongs in the extras log with a written agreement, before the work is done.
Two things that get decided while the walls are open and are expensive to change afterwards: where the washing machine and tumble dryer connections go, and whether the smoke alarms are wired the way the rules require.
First fix is everything that happens before the walls and floors close: pipe runs, cable runs, stud walls and door linings. Second fix is what comes after boarding and plastering: sockets, taps, radiators, doors. These are trade terms, used here the way the builders' merchant Travis Perkins sets them out (First fix vs second fix, read 27 September 2026). The checklist lives at the boundary, because that is the last moment checking is free.
Because for the next thirty years, every shelf you hang and every leak you trace starts with the question: where exactly does that pipe run? Photos with a tape measure in shot answer it in seconds. It is the cheapest insurance in the entire build and it costs ten minutes.
No. Where the law requires an inspection (structural work, drainage), your builder or building control arranges it, and new circuits are usually certified by a registered electrician; you should see the certificates afterwards. This checklist is the homeowner layer on top: the practical checks nobody is legally required to do for you.