Stairs

In most loft conversions the staircase is the problem that decides everything else. A compliant flight needs a long run on the floor below, and it has to land where there is enough height under the ridge to stand up. Get the position wrong and you lose a bedroom, or the loft does not work at all.

The rules come from Approved Document K, which sets the pitch, the rise and going of each step, and the headroom you need over the flight. A loft conversion gets one relaxation on headroom that the rest of the house does not, and there is a steep alternating-tread stair that Part K allows only in a narrow set of cases.

Where to start

Read the loft staircase guide first. It explains the Part K geometry, how much floor space a compliant flight actually needs, and why the stair position is the first thing to pin down, before the layout, before the quote.

Then, only if a standard stair genuinely will not fit, read the space-saver (alternating-tread) staircase guide. Part K allows these in one specific situation, and building control rejects them whenever the loft goes beyond it.

Where this fits in a loft conversion

The stair becomes part of the protected escape route once the loft adds a third storey, so it connects to the fire doors and alarms that line the stairway. Decide the stair position before the layout is fixed and before you sign a loft company's quote, because moving it afterwards is expensive.