Your roof structure sets the rules of the game.
Cut (traditional) roofs use individual rafters and purlins. They often leave clear space down the middle, which makes adding new floor joists, insulation and stairs straightforward. Loads transfer to walls and purlins; steel is sometimes needed but can be modest.
Trussed roofs (common from late 1960s on) use factory-made triangular frames. They’re efficient—but those web members occupy the very volume you want to inhabit. Conversions usually need a designed solution (steels, trimmed openings, new floor system) to carry loads once webs are cut or replaced.
How to tell quickly:
– Look for repeating timber triangles (trusses) vs separate rafters and purlins (cut).
– Check the age of the house and the loft photos.
– If in doubt, assume you’ll need an engineer.
Design implications:
– Stairs & headroom: trussed roofs often push you toward a modest dormer to create standing space over stairs and landing.
– Cost & program: more structure usually means more spend and coordination, but a clean design avoids nasty surprises later.
– Services: plan routes early—steels and new joists constrain duct runs and soil pipes.
What to do next:
Get an architect + structural engineer to scope a concept scheme with a load path, indicative steel sizes/positions, and insulation/ventilation build-ups. This early clarity saves money on site.
