How Much Does a Hip-to-Gable Loft Conversion Cost in 2026?
A UK hip-to-gable loft conversion typically costs £42,000–£68,000 in 2026 for the gable extension itself, plus £8,000–£14,000 if you add a rear dormer. Price is driven by roof structure (cut roof vs trussed — trusses need a steel-and-purlin redesign), gable scope (full hip removal vs half-hip), finished use (master suite vs simple bedroom), and the region. A typical 3-bed semi hip-to-gable + rear dormer + ensuite lands at £58,000–£72,000 in 2026 — a strong choice for end-of-terrace and semi-detached homes where a standard dormer alone wouldn't yield a usable double bedroom.
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How much is a hip-to-gable conversion in 2026?
Typical 2026 UK hip-to-gable conversion costs:
- Hip-to-gable only (single bedroom) — £42,000–£52,000
- Hip-to-gable + rear dormer — £52,000–£68,000
- Hip-to-gable + L-shape dormer + ensuite — £62,000–£78,000
- Double hip-to-gable (detached chalet) — £78,000–£105,000
- Hip-to-gable + mansard rear (conservation area) — £85,000–£120,000
Most hip-to-gable conversions on semi-detached and end-of-terrace homes fall under Permitted Development, but volume limits (40m³ terrace / 50m³ semi) and the cubic measurement of the new gable can push you into a full planning application. Always check before committing.
Hip-to-Gable Cost by Scope
A bare hip-to-gable conversion gives you a single decent bedroom. To make it a true master suite or a 4th-bedroom-with-ensuite that actually adds 5-figure value, you'll layer a dormer, an ensuite or both. Here's what each step realistically costs in 2026.
Hip-to-gable only — single bedroom
Hip rafters cut and removed, new gable wall built in matching brick or render to first-storey eaves height, two new Velux roof windows on the rear pitch, full structural steel ridge and floor support, insulation, plasterboard and decoration. One usable bedroom (roughly 16–20m²) and a small landing.
Hip-to-gable + rear flat-roof dormer
The most popular scope. Adds a full-width rear flat-roof dormer giving you proper standing headroom across most of the new floor, two large dormer windows, and enough room for a king bed plus wardrobes. Adds 8–14m² of habitable area beyond the bare hip-to-gable.
Hip-to-gable + L-shape dormer + ensuite
Common on Victorian and Edwardian semis with a rear outrigger. The dormer follows the L-plan over the kitchen below, giving an enormous master suite footprint plus a properly proportioned ensuite. Best ROI scope for £450k+ properties.
Double hip-to-gable (detached chalet bungalow)
Both hipped ends of a detached property are squared off into full gables — typically a chalet bungalow being converted into a true 2-storey home. This is essentially a small storey extension and almost always needs a full planning application.
Hip-to-gable + mansard rear (conservation area)
Where a flat-roof dormer would be refused on aesthetic grounds, a mansard with traditional double-pitch detailing, lead flashings and sash windows is often the only path forward. Heritage joinery and slates push the cost up sharply.
What Actually Drives the Final Bill
Two identical-looking 1930s semis on the same road can come back £15,000 apart on a hip-to-gable quote. These are the six factors that explain the spread.
1. Roof structure (cut vs trussed)
Pre-1965 cut-rafter roofs are simple to gable up — purlins and ridge are doubled, hip cut, gable wall built up. Trussed-rafter roofs (1970s+) need wholesale truss removal and replacement with a steel-and-purlin design. Trussed designs add £4,000–£8,000.
2. Gable height & brickwork
A standard semi gable is 3.0–3.6m of new brickwork. Render-finish properties are slightly cheaper than face-brick (£6.6k vs £8.4k typical). Houses with first-storey eaves above 5m (1930s with high parapets) push the brick cost up 20–30%.
3. Dormer scope
A small rear single Velux: included. A full-width flat-roof dormer: +£8k–£14k. Box dormer with bifold or Juliet balcony: +£12k–£18k. L-shape dormer over a Victorian outrigger: +£14k–£22k.
4. Wet services in the loft
No bathroom: baseline. Cloakroom WC + basin: +£3,200–£4,800. Full ensuite (shower, basin, WC): +£5,200–£8,800. The boiler often needs a system upgrade or a pumped pressurised supply for upper-floor showers — add £2,200–£3,800.
5. Stair position & landing
Stair over the existing first-floor stair (in line): cheapest. Stair pivoted 90° or 180° (more common where the stair sits at the front): adds joinery, structural openings and often loses a first-floor cupboard — +£2,200–£4,500. Bespoke oak open-tread stair: +£3,000–£6,500.
6. Region
London labour runs 30–42% above national average for loft work — much of which is craft scaffold work, harder to trim. South East +18%. Midlands and North sit at the national average. Wales and Scotland slightly below.
Hip-to-Gable Cost by UK Region
Based on 380+ recent UK hip-to-gable + rear dormer projects on 3-bed semi-detached and end-of-terrace homes (mid spec, with one bedroom + ensuite).
Note: Hip-to-gable is far less common in inner London (most properties are terraces, not semis) — what little inner-London volume exists is concentrated in 1930s semis in zones 3–6 and pushes labour rates up sharply.
Worked example (illustrative): 1930s Semi, Birmingham B17
3-bed semi-detached in Harborne. Hip-to-gable plus rear flat-roof dormer creating a master bedroom with walk-in wardrobe and full ensuite. Trussed roof rebuild. Completed February 2026.
| Architect drawings + Building Regs application | £2,650 |
| Strip-out + scaffold (8 weeks) | £3,400 |
| Truss removal + new steel ridge, purlins, floor steels | £8,200 |
| Gable wall: brick to match + insulated cavity | £8,800 |
| Rear flat-roof dormer build + GRP roof | £8,600 |
| Three dormer windows + flush trim | £2,400 |
| Insulation, plasterboard, skim throughout | £4,200 |
| Bespoke oak stair (14 tread) + balustrade | £3,400 |
| Ensuite: shell, plumbing, sanitaryware, tiling | £6,400 |
| Electrics, mains-wired alarms, LED downlights | £2,100 |
| Decoration + walk-in wardrobe joinery | £2,400 |
| VAT | £2,250 |
| Total (10 weeks on site) | £54,800 |
Valuation uplift: £445,000 pre-works → £528,000 post-works valuation (RICS appraisal, March 2026). Net value-add £28,200 after construction costs — and a 4th proper double bedroom that moved the home from 3-bed-semi to 4-bed-semi banding.
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