-
getting the steels in
This isn't always necessary, and something I'd want to avoid: old houses aren't designed to carry additional steel beams, getting them in is disruptive and expensive, it's a big material/resource impact. I've worked on quite a few loft conversions with reinforcement in small plywood and timber elements (joists, floors, webbing where bits of trusses are removed) and it's a much more pleasant process when all the pieces can be carried manually. You do need a willing structural engineer whose solution does not default to steel beams.
This is 'sometime in the future' thinking - but has anyone done a loft conversion which is like posh boarding out with insulation in the rafters, ceiling and floor added, but no rooms? That's what I'd like to do - with 1 opening rooflight and an electrical socket or two. Maybe no fixed stair (so it doesn't become a 'habitable room'). Basically to make it a warm controlled space instead of a cold draughty space.