24/06/2026
What does a loft conversion actually cost in 2026?
Most homeowners never get a straight answer. Ask three builders, get three vague numbers, all with room to creep up once work starts. So here is a real one. A full loft conversion for £55,000, every line laid out.
The £5,000 before any building begins is the part people skip and regret. Architectural drawings, structural engineer calculations and building control fees are what stop your loft becoming a problem later. Skip the planning and you pay for it twice.
Structural works at £9,000 are the steel and support that let your roof carry a proper room. You never see it once it is done, but it is the difference between a safe conversion and a sagging ceiling.
The dormer at £15,000 is your biggest cost and your biggest change. It turns a cramped triangle into a room with real headroom. Windows and rooflights at £3,000 bring the light in, and a staircase at £2,000 gives you a safe way up, not a ladder to an afterthought.
The rest makes it liveable. Plumbing and electrics at £7,000, insulation and fire upgrades at £6,000, internal finishing at £8,000. The work that keeps it warm in January and safe all year.
£55,000, fully accounted for. No surprise phone calls. No found problems that double the bill. A proper plan tells you where every pound goes before you commit one.
That extra bedroom or office might already be sitting above your head. The only question is whether your roof can take it, and a real builder can tell you that in one conversation.
DM ‘LOFT’ or visit designedtobuild.co.uk to find out what your conversion would actually cost.
