The drawing said the alcove would be 96 in wide. When I turned up to install, it was 94 3/4 in, because somebody had strapped the masonry wall to take a run of conduit and nobody thought to tell the shop. That cabinet went back on the truck. Building a piece for a room that has not been framed yet is normal work, but it only works if you agree, in writing and early, on five moments where the shop and the site have to compare numbers. Miss any one of them and the piece is either too big or floating on packers.

Checkpoint one: the framing dimension, not the drawing dimension

Architectural drawings give finished dimensions. Framers work to stud lines. Between those two numbers sits drywall — 1/2 in a side normally, 5/8 in where a fire rating or a sound assembly is involved, and sometimes two layers — plus whatever strapping the mechanical trades add. The number the bench needs is the finished opening, measured or committed to, with a note saying which wall board thickness it assumes. When the alcove is being built specifically to receive a piece, the cleanest arrangement is for the opening to be framed 1 in oversize in each direction and for the piece to carry scribes to suit. Nobody loses that way.

Checkpoint two: floor build-up and the finished floor line

A tall unit is set out from the finished floor, and the finished floor often arrives last. Engineered timber over underlay is typically 5/8 to 3/4 in; tile over a decoupling membrane on a mortar bed can be 1 1/4 in or more. If the piece is built assuming one and installed on the other, the toe kick is wrong and the crown detail at the ceiling stops being parallel to anything. The pragmatic answer is a separate plinth, made and scribed on site after the floor is down, with the carcase landing on it. It costs an hour and removes the single most common argument between a joinery shop and the builders handling the addition.

Checkpoint three: services inside the wall

Anything that lands inside the footprint of the piece has to be located before the carcase is drilled: outlets, data, a radiator pipe rising in a corner, a return air path, the back box for a wall-mounted screen. The useful artefact here is a photograph of the open wall with a tape laid across it, taken before the drywall goes on, and that photograph should be requested as a deliverable rather than hoped for. Cutting a 4 in hole in the back of a finished cabinet on site is possible; cutting it in the right place without a photograph is luck.

Checkpoints four and five: the ceiling and the sequence

Ceilings in new additions are rarely level to the standard a full-height unit demands — 1/4 to 1/2 in of fall across a 12 ft room is common and within normal building tolerance. A unit that runs to the ceiling therefore needs either a scribed filler panel at the top, typically 2 to 3 in deep, or a deliberate shadow gap that makes the variation invisible. The last checkpoint is sequence: the piece should land after painting and before the finished floor if it sits on a plinth, or after the floor if it is a simple base unit. Getting a written sequence on the programme, with a two-day window rather than a date, is what keeps a finished cabinet from sitting under a drywall sander.

Frequently asked questions

Can a built-in be made entirely from drawings with no site measure? It can, provided every interface is detailed with a scribe or a filler and the piece is designed slightly undersize. What cannot be done safely is a tight-fit piece from drawings alone.

Who is responsible if the opening is framed wrong? In practice it is settled by whichever party last confirmed the number in writing, which is the reason to confirm it in writing at each of the five checkpoints rather than over the phone.

How much lead time does a built-in need relative to the construction programme? Allow six to ten weeks from approved drawings for a made-to-measure piece in hardwood, longer if veneer is being sequence-matched, and start the drawings at the framing stage rather than at first fix.