The short answer
A hip-to-gable loft conversion typically costs £35,000–£60,000, often combined with a rear dormer to maximise space. It suits semi-detached and end-of-terrace homes with a hipped roof. See overall loft conversion costs for a comparison across all types.
A hip-to-gable conversion is not available to every homeowner — it only applies to properties with a hipped roof, where the roof slopes inward on the end rather than meeting a vertical gable. Those who do qualify often find it produces significantly more space than a rear dormer alone. Understanding the cost, the planning position and what the build involves helps you decide whether the premium over a simpler conversion is justified for your home.
Hip-to-gable costs at a glance
- Hip-to-gable only £35,000–£50,000
- Hip-to-gable + rear dormer £45,000–£65,000
- Detached (both ends) £50,000–£75,000+
- Planning permission Usually required
- Best suited to Semi-detached and detached homes with hipped roofs
- Space gained Large — adds significant new triangular volume
What a hip-to-gable conversion involves
A hipped roof has four slopes — two at the front and rear and one sloping inward at each end. In a semi-detached house, the party end is typically a gable wall, but the road-facing or garden-facing end is hipped. A hip-to-gable conversion rebuilds that hipped end as a vertical gable wall, gaining the full triangular volume of space that previously sloped away. The resulting new gable is typically built in blockwork matching the existing walls, and the new gable end is finished externally to match the house. The work is structural: the existing hip rafters are removed, a new ridge beam may be extended or replaced, and the new gable wall ties into the party wall or existing structure. It is a more complex and material-intensive job than a dormer, which adds to cost.
Hip-to-gable and rear dormer combined
In many semi-detached houses, the hip-to-gable conversion alone produces a reasonable room but the restricted depth of the floor area means the space is still dominated by sloping ceilings on the rear slope. Combining a hip-to-gable with a full-width rear dormer maximises the new room’s floor area and head height simultaneously. This combination is the most popular approach for semi-detached properties and typically adds 30–40 m² of usable space. It is also the most expensive of the mainstream conversion types — see the cost table below for typical ranges.
| Scope | Typical cost |
|---|---|
| Hip-to-gable only | £35,000–£50,000 |
| Hip-to-gable + rear dormer, single room | £45,000–£60,000 |
| Hip-to-gable + rear dormer, bedroom + en suite | £50,000–£65,000 |
| Double hip-to-gable (detached) | £50,000–£75,000+ |
| London & South-East premium | Add 20–40% |
Planning permission
Hip-to-gable conversions almost always require planning permission because they materially change the external appearance of the house — the end elevation changes from a hipped slope to a vertical gable. Permitted development rules permit roof enlargements up to certain volume limits, but the hip-to-gable change is typically too significant a visual alteration to qualify without an application. You will need architectural drawings and a planning application to your local authority, adding around £1,500–£4,000 in architect’s fees plus the planning fee (£258 in England). If your neighbour has already done a hip-to-gable, that can support your application but does not guarantee approval — see planning permission for loft conversions.
Is it worth the extra cost?
Whether a hip-to-gable conversion justifies the premium over a simpler dormer depends on your property and what you want the new space to do. In a 1970s semi where the rear slope alone would give a tight and awkward room, the combined hip-to-gable-and-dormer option can transform the project — turning a marginal single room into a generous bedroom with en suite and dressing area. In terms of added value, adding a usable double bedroom with en suite in the right market can be among the highest-returning home improvements. See does a loft conversion add value? for an evidence-based look at the return. This page provides general information on typical costs, not a quote or professional advice. Actual costs depend on your specific property — always consult qualified specialists and your local planning authority.
Get a quote for your hip-to-gable conversion
A specialist can confirm whether your roof is hipped, assess the planning position and provide a fully scoped quote for the hip-to-gable or combined hip-to-gable-and-dormer option.
Frequently asked questions
How much does a hip-to-gable loft conversion cost?
Typically £35,000–£60,000 for a hip-to-gable conversion alone, or £45,000–£65,000 when combined with a rear dormer. London and South-East projects are typically 20–40% more.
Does a hip-to-gable need planning permission?
Almost always, yes. The change to the end elevation is typically too significant to qualify as permitted development. You will need architectural drawings and a planning application, adding around £1,500–£4,000 in architect fees.
Is a hip-to-gable conversion only for semi-detached houses?
No — it applies to any property with a hipped roof end, including detached houses (where both ends can be converted) and end-of-terrace properties. It is not available to terraced houses with existing gable ends.
Can I combine a hip-to-gable with a rear dormer?
Yes, and this is the most popular approach for semi-detached homes. Combining the two maximises usable floor area and headroom. The combined project typically costs £45,000–£65,000 and adds the most space of any single-side conversion.
Sources & further reading
- Planning Portal — planning permission requirements for roof alterations and hip-to-gable conversions
- LABC (Local Authority Building Control) — building regulations requirements for structural alterations
- GOV.UK — Party Wall etc. Act 1996 and party wall notice requirements
- RICS — guidance on home improvement added value and property valuations
This is general information about loft conversions in the UK, not professional planning, structural, building or legal advice. Costs are typical illustrations, not quotes; timescales and outcomes vary with your property, location and chosen specialist. Always consult a qualified specialist and your local planning authority before starting work.