Hip-to-gable loft conversions in London for semis and end-of-terraces

Published London guides for 2026 put a hip-to-gable with a rear dormer at £63,000–£93,000. That is the median of several companies' ranges, not our quote, and some of the sources include VAT while others do not. On top come the certificate or planning fee, building control, the party wall surveyor and sanitaryware. A hip-to-gable without a dormer costs less but gives head room rather than floor, which is why the two are almost always built together.

Usually not: on a semi or detached house a hip-to-gable is permitted development within the 50 cubic metre allowance. Permitted development only restricts the roof slope on the principal elevation facing the road; on a corner plot the borough may treat the road-facing side as a principal elevation, which we check first. You do need permission in a conservation area, on an Article 4 street, for a flat, and where the gable and dormer together exceed the allowance (Planning Portal, loft conversions, checked September 2026). Confirm with your borough; a lawful development certificate settles it.

Any house with a hipped roof and a free side: the 1930s semi-detached houses across outer London are the classic case, followed by end-of-terrace houses with a hipped end, bungalows and detached houses, which can take a gable at both ends. A mid-terrace has no hip to convert and takes a dormer instead. A semi on a corner plot still suits the conversion structurally, but where the borough treats the road-facing side as a principal elevation it needs a planning application rather than a certificate.

Nearly always, if the aim is floor area. The gable on its own raises the ceiling along the full length of the ridge, which is worth having, but the rear slope still limits how much of the loft you can stand in. A rear dormer built out to the new gable is what produces a full-width bedroom with room for an en-suite, and the published London prices describe that combination. The two are designed and built as one job.

Yes. A staircase is internal work, and planning permission is only concerned with the outside of the building. What the stair does need is Building Regulations approval: two metres of headroom over the flight, reduced to 1.9 and 1.8 metres under a slope, a compliant pitch, a landing at the top (Approved Document K, checked September 2026), and the fire-protection work that follows from adding a storey. A loft reached by a ladder can be storage; a loft reached by a compliant stair with a certificate can be a bedroom.

Since 25 April 2024, building work done without planning permission in England becomes immune from enforcement only after ten years; work substantially completed before that date keeps the old four-year limit (gov.uk planning enforcement guidance, checked September 2026), so check the position with your council. A new gable is visible from the street and a buyer's solicitor asks for the certificate, so on a hip-to-gable the rule is no substitute for a lawful development certificate; our loft conversion cost guide covers it in full.

Your attached neighbour has to be notified rather than asked. The floor steels bear on the party wall, so a party structure notice goes to them at least two months before work starts. If they consent in writing, the job proceeds; if they do not reply within 14 days, the Act treats it as a dispute and surveyors produce an award setting out how the work is done and protected. The gable itself, on the detached side of a semi, is not party wall work at all.

A Velux conversion in a roof that already has the height, with the stair continuing the existing flight and no en-suite; the published London range starts around £30,000. On a hipped roof, though, the slope on three sides leaves only a strip of usable floor, so a hip-to-gable at £63,000–£93,000 usually gives better value per usable square metre on a semi. The loft conversion cost guide compares every type.

Not a hip-to-gable: the published London ranges start at £63,000 with a rear dormer, and the cheapest advertised starting figures leave out the fire-door work on the floors below and the fees. If the budget is fixed at that level, boarding the loft for storage is honest and calling it a bedroom is not; the loft conversion cost guide explains what each type costs and why, including the rooflight conversion that starts around £30,000.

The approvals run first and usually take longer than the build: eight weeks or so for a lawful development certificate or a planning application, and two months for the party wall notice, which we serve at design stage so the two periods overlap. On site, the gable adds a stage to a plain dormer programme, because the flank scaffold, the blockwork and the ridge extension come before the dormer can be framed. We give the on-site programme for your roof with the quotation.