The design and position of the staircase is a key decision in a loft conversion, as it will dictate how much of the storey below is lost to create access. The stairs must land where there is at least 1.9m of headroom (and 1.8m at the sides), which can limit options.
The steeper and narrower a staircase, the more space efficient it is. The maximum pitch under Building Regulations is 42° and although there is no minimum width for a staircase, less than 600mm is unlikely to prove practical. A spiral staircase is one of the most space-efficient options available.