Hip to Gable Loft Conversion Cost UK (2026): Full Price Guide

How much does a hip to gable loft conversion cost?

Many semi-detached and detached houses built between the 1920s and 1970s have a hipped roof: the side of the roof slopes inwards as well as the front and back. That sloping side eats into the loft, leaving little usable floor space. A hip to gable conversion builds the end wall up into a vertical gable and extends the ridge across, so the loft becomes a full-width, rectangular space.

Because it means rebuilding part of the roof and building a new section of external wall, a hip to gable costs more than a simple dormer. Published 2026 figures cluster around these ranges:

• HomeOwners Alliance (July 2026, using Checkatrade data): average about £60,000.
• MyBuilder (August 2026): £50,000–£70,000 on average, and £60,000+ in London.
• MyJobQuote (October 2026): £35,000–£50,000 for an average semi, up to £60,000–£75,000 for a large detached house.
• PlanWatch (October 2026): £55,000–£80,000, or £75,000–£100,000 in London.

The spread mostly reflects what is included. The lowest figures are builders’ prices for the core work; the higher ones include a rear dormer, professional fees and VAT.

Hip to gable cost by size

A hip to gable on its own typically creates 20–30m² of usable floor space; adding a full rear dormer often takes it to 30–40m². The table uses our calculator’s all-in figures for a standard finish.

Usable floor area	Typical layout	Estimated total cost (standard finish)
25m²	Double bedroom	£47,000 – £67,500
30m²	Double bedroom with shower room	£56,000 – £80,000
35m²	Bedroom suite (usually with rear dormer)	£65,000 – £93,000
40m²	Two bedrooms or bedroom plus study	£74,000 – £105,500
45m²	Large suite, often double hip to gable	£83,000 – £118,000

Hip to gable cost per m² and by finish

MyJobQuote puts hip to gable conversions at £1,600–£2,500 per m², compared with £1,500–£2,000 for a dormer. Our build-only rates (excluding VAT and fees) are in the same territory:

Finish level	Build cost per m² (ex VAT)	30m² all-in (Midlands)
Basic – rendered or tile-hung gable, standard fittings	£1,350 – £1,780	£51,000 – £72,000
Standard – brick-matched gable, mid-range shower room	£1,480 – £2,000	£56,000 – £80,000
High-end – large gable glazing, quality en-suite, bespoke stairs	£1,830 – £2,430	£68,500 – £96,500

Cost by type of hip to gable conversion

Project	Typical 2026 cost	Typical property
Single hip to gable only	£35,000 – £50,000	Average semi-detached or end-terrace
Hip to gable with rear dormer	£55,000 – £75,000	Semi-detached (the most common combination)
Double hip to gable	£50,000 – £75,000+	Detached house hipped on both sides
Large detached, hip to gable	£60,000 – £75,000	Large detached house

Hip to gable with rear dormer cost

On its own, a hip to gable still leaves a sloping rear roof, which limits headroom. That is why most semi-detached conversions add a full-width rear dormer at the same time. MyBuilder estimates the rear dormer adds £10,000–£15,000; MyJobQuote puts the combined project at £55,000–£75,000, starting from about £50,000. In our calculator, a 35m² hip to gable with rear dormer comes to around £65,000–£93,000 all-in in the Midlands. Doing both together is far cheaper than adding a dormer later, because you pay for scaffolding, design and building control once.

Double hip to gable cost

A detached house with hips on both sides can have both converted to gables – a double hip to gable. It creates a very large loft, often enough for two bedrooms and a bathroom. MyJobQuote estimates about £50,000–£75,000 or more. Expect more scaffolding, two new gable walls and larger steels. Volume is the catch: two gables plus a rear dormer can exceed the 50m³ permitted development limit, so a planning application may be needed.

Hip to gable costs by region

Region	Build cost per m² (ex VAT)	30m² hip to gable, all-in
London	£1,850 – £2,500	£71,000 – £101,000
South East	£1,658 – £2,240	£63,500 – £91,000
South West & East of England	£1,539 – £2,080	£59,000 – £85,000
Midlands	£1,450 – £1,960	£56,000 – £80,000
North of England & Wales	£1,362 – £1,840	£52,500 – £75,500
Scotland & Northern Ireland	£1,421 – £1,920	£55,000 – £78,500

Hip to gable conversions are especially common in outer London suburbs full of 1930s semis. MyJobQuote’s London data puts a 30m² hip to gable at £52,000–£69,000 (build price), while PlanWatch gives £75,000–£100,000 for London all-in. See our London loft conversion cost guide for more.

Full cost breakdown

Cost item	Typical cost	Notes
Building work	£1,350 – £2,430 per m² ex VAT	Gable wall, roof alteration, steels, floor, stairs, electrics, plastering
Design and drawings	4–7% of build cost	Often bundled by loft specialists
Structural engineer	£500 – £2,500	Steels, new gable wall and ridge
Building control	£600 – £1,200	Always required
Lawful development certificate / planning	£274 / £548	England fees from 1 April 2026
Party wall surveyor	£1,000 – £3,000 per neighbour	Usually one neighbour on a semi
Rendering the new gable	£3,500 – £4,500	If not built in matching brick (MyJobQuote)
En-suite	£5,000 – £10,000	MyJobQuote range
VAT and contingency	20% VAT; 10% contingency	VAT not charged on the planning fee

MyBuilder’s split for a typical project: £35,000–£50,000 for build and labour (60–70% of the total), £10,000–£15,000 for materials and roofing, and £5,000–£10,000 for extras such as planning and electrics.

What affects the cost?

Gable wall construction

The new gable can be built in brick or block to match the house, or as a lighter timber frame finished in render or tile hanging. Matching brickwork looks best but costs more, especially for older or unusual bricks.

Roof structure and tiles

Trussed rafter roofs need more steelwork than traditional cut roofs. Matching old clay or concrete tiles across the extended roof can also be costly; PlanWatch estimates £1,500–£3,500 for tile matching.

Chimneys and services

A chimney stack on the hipped side may need to be rebuilt, supported or removed, and a cold water tank or boiler flue may need relocating.

Dormer, windows and en-suite

Adding a dormer, gable-end glazing, extra rooflights or an en-suite are the biggest variables after size.

Hip to gable planning permission

In England, a hip to gable conversion on a house is usually permitted development, so a planning application is not normally needed. The new roof volume counts towards the allowance of 50m³ for semi-detached and detached houses (40m³ for an end-terrace), together with any rear dormer. Other conditions include:

• The new roof must not be higher than the existing ridge.
• Nothing may extend beyond the front roof slope facing a road.
• Materials must be similar in appearance to the existing house.
• No balconies or raised platforms; side windows must be obscure-glazed and fixed below 1.7m.

Planning permission is needed in conservation areas, National Parks, National Landscapes and World Heritage Sites, for flats and maisonettes, where an Article 4 direction removes rights, or when you exceed the volume limit – a real risk with double hip to gables. Get a lawful development certificate (£274) even if you are confident; it is quick proof for buyers. Building regulations approval is always required. Our loft conversion planning guide explains the rules in full.

Party wall notices

On a semi, steels often bear on the party wall, so you must serve a party wall notice on your neighbour at least two months before work. If they consent in writing, there is no surveyor cost; if they dissent, budget £1,000–£3,000.

How long does it take?

1. Design, survey and structural calculations: 2–6 weeks.
2. Lawful development certificate or planning: up to 8 weeks; party wall notice periods run at the same time.
3. Build: MyJobQuote gives 6–8 weeks for a hip to gable and 7–9 weeks with a rear dormer; larger or double conversions can take 10 weeks or more.
4. Completion: 1–2 weeks for snagging and building control sign-off.

How to save money

• Do the gable and dormer together – one set of scaffolding, one design fee and one building control application.
• Consider a rendered gable if matching brick would be expensive and the street has rendered houses.
• Stay within 50m³ to avoid a planning application and delays.
• Get neighbours onside early to avoid party wall surveyor fees.
• Ask for itemised quotes from at least three loft specialists, so you can see what steelwork, stairs and finishes are included.

Does a hip to gable conversion add value?

MyBuilder estimates a hip to gable conversion can add up to 20–25% to a home’s value, broadly in line with Nationwide research (cited by Which?) that a loft conversion adding a bedroom and bathroom can add up to 24%. Because a hip to gable creates a full-height, regular-shaped room, it usually adds more useful space than a dormer alone – a strong selling point on a three-bed semi becoming a four-bed.

Still deciding? Compare with our dormer loft conversion cost guide or the overall loft conversion cost guide.

Hip to gable FAQs

How much does a hip to gable loft conversion cost?

Most cost £50,000–£80,000 all-in, with an average around £60,000 (HomeOwners Alliance). Our calculator puts a 30m² standard-finish conversion at £56,000–£80,000 including fees and VAT in the Midlands.

How much does a hip to gable with rear dormer cost?

Typically £55,000–£75,000 according to MyJobQuote, with the rear dormer adding around £10,000–£15,000 (MyBuilder). A 35m² project comes to about £65,000–£93,000 all-in in our calculator.

Do you need planning permission for a hip to gable?

Usually not, if the house is not in a conservation area or other designated land and the total new roof volume stays within 50m³ (40m³ for an end-terrace). Building regulations approval is always needed.

How much does a double hip to gable cost?

MyJobQuote estimates around £50,000–£75,000 or more for a detached house with both sides converted, before any rear dormer.

Is hip to gable more expensive than a dormer?

Yes – typically by around £10,000, because you build a new gable wall and extend the ridge. The HomeOwners Alliance averages are about £60,000 for hip to gable and £50,000 for a dormer.

Can you do a hip to gable on a semi-detached house?

Yes – it is the most common property for it. Your neighbour’s half stays hipped, which some councils dislike, but under permitted development the work is usually lawful. Steels in the party wall mean serving a party wall notice.

Related guides: Loft conversion cost calculator · Party wall agreements · Lawful development certificate

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