Walls and ceilings
NHBC's standards judge walls and ceilings from 2m away, in natural daylight, with no artificial light shining on the surface. Wall lights and uplighters should be off. That rule matters. The NHQB says marks you can only see under particular lighting, or from certain angles, aren't snags.
From 2m, board joints shouldn't be readily visible. Walls should be reasonably even, with no visible gaps between the wall and fittings such as switch plates. Some texture differences round lights and fittings are allowed. The official checklist adds popped screws and jointing tape that isn't fully covered.
If you want a number, NHBC allows up to 3mm of deviation under a 450mm straight edge for plastered and dry-lined walls. Ceilings should be level within 3mm per metre.
A trick we used a phone spirit-level app on a door frame or windowsill. It is only a rough check, but it told us where to look harder.
Are cracks in a new build normal?
Small ones usually are. NHBC's standards say cracks up to 2mm wide may appear where walls meet floors and ceilings, as materials shrink. NHBC's cracking guide says the edge of a £1 coin is about 3mm, if you have no ruler.
On the day, note any crack you can see, with a photo. Most appear later, as the house dries out. The year one page covers which cracks are normal and which need reporting.
Paint
Paint should be even, free from obvious runs and heavy brush marks, with nail holes and joints filled. NHBC judges it from 2m in daylight, again without shining a light on it. The official checklist adds paint splashes on switches and sockets.
NHBC also lists what to expect. Touched-up patches can be a slightly different colour, and painted skirting can look different from factory-finished doors.
What gap should there be round an internal door?
The gap between the door and the frame, at the top and sides, should be 4mm or less, and even. The frame should be within 5mm of upright over its height. The gap under the door to the bare floor should be between 10mm and 22mm. It leaves room for carpet and lets air move between rooms.
Open and close each door. Try the handle and the catch. A door that rubs or catches on the frame goes on the list. Fire doors have their own, tighter rules; the windows and doors page covers those.
Windows
Check that each window opens, closes and locks, without catching. The handles, stays and catches should work and sit square, and there should be a seal all round the frame. Keys should be there.
Glass is judged from at least 2m in daylight (3m for toughened, laminated or coated glass). Fine scratches up to 25mm long, and small bubbles that aren't obvious or bunched together, are accepted. The strip within 6mm of the edge of the pane doesn't count. Report scratched glass at once. NHBC's warranty doesn't cover cosmetic damage reported more than seven days after completion.
How do I test the sockets?
Plug a socket tester into each one. It is a small plug with lights that shows whether the socket is wired correctly. The official checklist asks for every socket to be tested this way, and for sockets and switches to sit level and flush with the wall. Try each light switch too. Every bulb should work.
That is as far as a buyer should go. Anything more is for an electrician. The electrics page covers the fuse box and alarms.
Radiators
Turn the heating on before you start, so the radiators have time to warm up. Each should work, be undamaged and level, with the wall behind it decorated and no leaks at the valves. A radiator colder at the top than the bottom usually has air in it. The heating page covers that.
Skirting and sealant
The gap between the bottom of the skirting and the bare floor should be 5mm or less at completion. Joints should look continuous from 2m. NHBC warns the gap can grow as the house dries out.
Sealant (the flexible filler along joints, sometimes called mastic) should be smooth and neat, without blisters or gaps.
Floors
Floors should be level within 3mm per metre across the room, and flat within 5mm under a 2m straight edge. You won't measure that on the day. Walk every part of the floor instead. The official checklist asks for floors that are flat, without excessive creaks, and carpets without ripples or lumps, with threshold bars at doorways.
A trick we used a marble on the floor. If it rolls off firmly in one direction, it is worth a closer look. It isn't a measurement.