Interiors usually get treated as the last phase. The building goes up, then somebody thinks about finishes, joinery and lighting. By then most of the decisions that determine whether a room works have already been made, quietly, by people who were not thinking about them as interior decisions at all.

Take lighting. A stepped ceiling with concealed cove lighting is one of the most requested things we do, and it is largely settled at first fix. The coffer needs depth, the run needs a driver somewhere accessible, and the switching needs to have been drawn before the walls were closed. Decide it late and you get a surface-mounted compromise pretending to be the thing that was wanted.

Or joinery. A fitted kitchen island with a solid worktop wants a floor that is flat and a slab that can take the load, and both are decided long before anyone picks a finish. Built-in wardrobes want walls that are true. A media wall wants services behind it. None of that is expensive if it is anticipated and all of it is expensive if it is not.

This is the practical argument for holding interiors inside the same appointment. It is not that one team has better taste. It is that the decisions are not sequential in the way the trades are. Somebody has to be thinking about the finished room while the walls are still open, and that is much easier when it is the same studio that will be standing in the finished room at handover.

Where interiors are a separate appointment, and often they should be, the fix is the same: get the interior designer involved at first fix rather than at painting. The cost of that involvement is small. The cost of not having it shows up in every room, in details that are almost right.