Why the door is a red herring
A doorway is a flat opening. You can present a sofa to it at any angle you like, and even a narrow street door between two shopfronts will usually take something bigger than it looks.
The turn is a three-dimensional problem. The width of the stair, the depth of whatever landing there is, the ceiling above it and the newel post all constrain each other at once — and in a flat above a shop that turn is usually immediate, because the stair starts at the pavement and has to get somewhere fast.
Four measurements
Take these with a tape, not by eye:
- The clear width at the narrowest point — post to wall, not doorway to doorway.
- The depth of the landing or the turn, from the top step to the far wall.
- The ceiling height directly above the turn. Everybody forgets this and it is frequently the deciding one.
- The diagonal of the item — its longest face corner to corner, rather than the dimensions on the listing.
"It came in, so it will go out" is not reliable
Sometimes it is true. Often it is not, because the flat has been reconfigured since — a partition wall, a replaced bannister, a boxed-in meter cupboard at the turn. Any of those changes the answer.
It is also possible the item came in through a window, and nobody mentioned it.
If it will not go
Three honest options, and it is far better to pick one in advance:
- Take it apart. Many sofas have removable feet, backs or arms, and most wardrobes were flat-pack once.
- Go through a window. Genuinely possible above a shop, needs planning and equipment, and needs the business below to know about it.
- Do not take it. Sell it, and buy something that fits the next place.
And measure the next place first
If you are moving from one SE15 flat to another, the turn at the new one matters as much as the one at this one. Measure both before you decide what is coming.