Space-saving designs such as alternating treads or compact spirals must still meet building regulations for rise, going and handrails.
Use high-performance insulation boards between rafters and add a continuous layer across the ceiling to reduce heat loss.
Many loft conversions fall under permitted development, but flats, listed buildings and some conservation areas will need a formal application.
Structural changes, new staircases and altered fire escapes usually require approval to ensure the work is safe and legally compliant.