Loft Conversions in London

Most dormer and Velux loft conversions fall under permitted development — no planning permission needed — provided the dormer does not project forward of the front roof slope, and the total volume added is within 40 cubic metres (terraced) or 50 cubic metres (detached/semi). Properties in conservation areas and mansard conversions usually need a full planning application. We check this during your free site visit.

The key factor is head height. You need a minimum of 2.2 metres from the top of the ceiling joists to the underside of the ridge beam. Most London houses built before 2000 have enough height. We also check whether your roof uses cut timber or trussed rafters (trussed roofs need more structural work), and assess staircase positioning. All of this is covered in your free site visit.

A dormer extends outward from the rear roof slope, adding headroom and floor area at the back of the loft. A hip-to-gable extends the sloping side of the roof to a vertical wall, increasing the overall width of the usable space. Hip-to-gable is only possible on semi-detached and detached homes with hipped roofs. Many clients combine both for maximum space — a hip-to-gable with a rear dormer.

A rear dormer loft conversion typically costs £38,000–£55,000. A hip-to-gable with rear dormer ranges from £45,000–£65,000. Mansard conversions start from around £55,000. Prices depend on the existing roof structure, staircase opening, and your finish choices for the bedroom and en-suite. Our fixed-price quotation includes structural steelwork, insulation, plastering, electrics, plumbing, staircase, and building control fees.

If your conversion involves work on or near a party wall — common on terraced and semi-detached houses — you will need to serve a party wall notice at least two months before work starts. Rear dormers on terraced houses can sometimes affect neighbours' light, though this is rarely a planning issue under permitted development. We walk you through every obligation during your consultation.