Hip to Gable Loft Conversion Cost London 2026: Prices, Planning and What to Expect
Updated: 1 day ago
A hip to gable loft conversion is the standard answer for a 1930s semi-detached or end-of-terrace house with a hipped roof: the sloping hip end is rebuilt as a vertical gable wall, usually with a rear dormer behind it, and the narrow strip under the ridge becomes a full-width bedroom and en-suite. In 2026 our fixed price for a hip to gable with rear dormer starts from £60,000 inc. VAT (£50,000 + VAT), design and build inclusive.
Not sure whether you need planning permission? Five questions about your house and your project, and you see whether it is permitted development and the fixed from-price.
On most semis it is a fixed-price permitted development project: no planning application, Lawful Development Certificate included, economy specification. This guide gives you the range by configuration, what is in the figure, what moves it, and how to get an itemised estimate for your roof. The hip to gable permitted development guide covers the 50 m³ rule; Bohun Grove EN4, our LABC Building Excellence Award 2024 winner, is a hip to gable with rear dormer and rear extension built in one programme.
How Much Does a Hip to Gable Loft Conversion Cost in London in 2026?
The figure depends on the floor area under the new roof, whether a rear dormer is included (it almost always is), the specification of the bathroom and finishes, and the structure of your existing roof. Prices below are for the complete job — design, structural engineering, building control, construction, staircase, insulation, electrics, plumbing and finishes — from our published master table:
Hip to gable with rear dormer, economy specification: from £60,000 inc. VAT (£50,000 + VAT), typically £60,000 – £80,400 inc. VAT (£50,000 – £67,000 + VAT). A double bedroom with en-suite shower room and eaves storage — the most common conversion on a 1930s semi.
Larger floors, two rooms, mid-range or high-end specification: £80,400 – £114,000 inc. VAT (£67,000 – £95,000 + VAT). Two bedrooms or a bedroom plus study, a full bathroom, better sanitaryware, tiling and joinery.
Hip to gable with rooflights only (no dormer): priced individually. It keeps the roofline but gives far less usable floor, so on most semis we recommend the dormer combination — the extra structure costs less than it looks per square metre of room gained.
What Is a Hip to Gable Loft Conversion?
A hipped roof slopes on all four sides. In a hip to gable conversion, the sloping hip end — typically the side wall of a semi-detached or end-of-terrace house — is replaced with a straight vertical gable wall. This pushes the roof line out to the edge of the property and creates a much larger, more usable loft space.
Hip to gable conversions are almost always combined with a rear dormer loft conversion to maximise the floor space gained. Together, they create one of the largest possible loft spaces achievable within a semi-detached or end-of-terrace house.
What Affects the Cost of a Hip to Gable Loft Conversion in London?
Several factors influence the final cost of your hip to gable loft conversion. Understanding these will help you set a realistic budget.
Whether a rear dormer is included: A hip to gable conversion alone creates more headroom at the sides but limited floor space without a rear dormer. Adding a rear dormer typically adds £12,000 to £18,000 to the cost but makes the difference between a limited storage space and a full habitable bedroom.
Number of rooms created: A single bedroom with en-suite is the most common outcome. Adding a second bedroom, home office or bathroom increases the cost of internal fit-out.
Structural complexity: The hip to gable conversion requires new structural steelwork and roof reconstruction. The complexity depends on the existing roof structure, and older or more unusual roof designs can add cost.
Specification and finish: The quality of windows, bathroom fixtures, flooring, insulation and internal finishes varies widely and can add £5,000 to £15,000 to the overall cost depending on the level of specification chosen.
Where the house is: the final figure is postcode dependent — access, parking, scaffold and the condition of the existing roof move it more than the postcode itself. The instant estimate gives a range for your postcode in about two minutes; the fixed price follows the free consultation call and the survey.
Do You Need Planning Permission for a Hip to Gable Loft Conversion in London?
Most hip to gable loft conversions can be carried out under permitted development rights, meaning no full planning permission application is required. However, you will need to meet specific size and design criteria. The enlarged part of the roof must not exceed the highest point of the existing roof, and the materials used must be similar in appearance to the existing house.
A planning application is needed if the house is in a conservation area with an Article 4 direction, is listed, is a flat, or if the design goes beyond the permitted development limits (50 cubic metres on a semi or detached house). We check the designation and the planning history of your address before the design starts and obtain the Lawful Development Certificate as part of the job — book a free consultation call and we will tell you which route your roof is on.
How Long Does a Hip to Gable Loft Conversion Take?
A hip to gable loft conversion typically takes 10 to 14 weeks to build from the day work starts on site. The full project timeline from initial consultation to completion is usually 5 to 8 months, which includes the design stage (4 to 6 weeks), permitted development confirmation or planning permission if required (4 to 12 weeks), building regulations approval (2 to 4 weeks), party wall agreements (2 to 8 weeks) and the construction phase.
At LCCL Construction, we manage all pre-construction stages simultaneously where possible to reduce the overall timeline. You will have a dedicated project manager throughout keeping you informed at every stage.
Is a Hip to Gable Loft Conversion Worth the Cost?
Yes — on our projects and local sold prices, a well-planned hip to gable loft conversion usually adds more to the value of the home than it costs to build, and it is the only loft type that turns a hipped-roof semi into a genuine four-bedroom house. See our guide on how much value a loft conversion adds.
The practical benefit is equally significant — a hip to gable conversion with rear dormer creates a full master bedroom suite with en-suite bathroom, transforming a previously unusable loft into the most desirable room in the house. For more detail on the return on investment, see our guide on how much value a loft conversion adds to a London property.
Hip to Gable vs Other Loft Conversion Types
Hip to gable is the right choice if your property has a hipped roof — a dormer loft conversion alone won't create enough space in a hipped property. For terraced houses with a gable end already in place, a dormer or L-shaped loft conversion may be more appropriate. LCCL Construction will assess your roof type and recommend the most suitable conversion during a free consultation call.
Why Choose LCCL Construction for Your Hip to Gable Loft Conversion?
LCCL Construction is a loft conversion company in London based in Finchley N3, building hip to gable lofts across North London and Hertfordshire. We are LABC Building Excellence Award Winners 2024 for Best Residential Extension in London and London Regional Winners 2026 for Best Conversion or Alteration to an Existing Home, LABC Registered Partners and members of the National Federation of Builders.
As a design and build company, we handle everything from architectural drawings and planning through to structural engineering, building regulations, party wall agreements and construction. One company responsible for every stage.
Every estimate is itemised before any work begins, and the fixed price is in writing before you sign — it does not change unless you change the scope. Every loft carries a 12-month workmanship guarantee and a 10-year LABC structural warranty. Already have an architect's drawings? We price the build as drawn within seven working days.
Not sure whether your own house qualifies? Five questions, a straight answer and the from-price.
To book a free 30-minute consultation call about your hip to gable loft conversion, call LCCL Construction on 020 8037 7332 or get an instant estimate online — six questions, about two minutes. Finchley N3 based, covering all of London and Hertfordshire.
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