Loft Conversion Types
Hip to Gable Loft Conversions
If your house has a roof that slopes inwards at the side as well as the back, you're losing most of your loft to a shape. A hip to gable gets it back.
What a Hip to Gable Conversion Actually Is
A hipped roof slopes inwards on three sides instead of two. It's the standard roof on inter-war semi-detached and end-terrace houses, which means it's the standard roof across an enormous part of West London — Greenford, Perivale, Northolt, Southall, Harrow, Ruislip, Hayes and Wembley are built from little else.
It also wastes an enormous amount of loft. Because the side slopes inwards, the usable floor area narrows to a strip down the middle, and the walls are too low to stand near. Plenty of people look up there, see a triangle, and write the whole idea off.
A hip to gable rebuilds that sloping side as a flat vertical wall — a gable end, matching the one your neighbour's house probably already has. The roof is extended out over the new wall, and the loft goes from a narrow strip to a proper rectangular room.
Is Your Roof a Hip to Gable Candidate?
You Almost Certainly Are
If you're in a semi-detached or end-terrace house built between roughly 1920 and 1950, and the roof slopes inwards above the side wall. That's the classic Metroland semi, and it's the single most common conversion in this part of London.
You May Be
If you're in a detached house with hips on both sides. Two hips can be built up, though it's a bigger job and the planning volume allowance starts to matter.
You Aren't, if You're Mid-Terrace
A mid-terrace has no hip — it's gabled at both ends already, so there's nothing to fill in. A rear dormer or an L-shaped dormer is your route.
You Probably Aren't, if the Ridge Is Low
A hip to gable adds width, not height. If you can't stand up in the middle now, widening the middle doesn't fix it.
What the Work Involves
The Gable Wall
The hip is stripped and a new gable end is built up in blockwork or brick, faced to match the existing house. This is the visible change from the street side.
Structure
Steel beams carry the new floor and the roof over the extended span. This is why a hip to gable is a building-control job from the start, not a decorating job.
The Stairs
A permanent staircase, not a ladder. This usually takes space from the landing or a bedroom below, and it's the part people underestimate.
Fire Safety
In a two-storey house the existing stairway becomes your escape route, so it has to be protected — fire doors onto the stairs, a 30-minute fire-resisting floor, and mains-powered interlinked smoke alarms on every level.
Insulation and Finish
Roof and gable insulated to current standards, then the room is finished like any other.
Most hip to gables are paired with a rear dormer at the same time. The gable gives you width, the dormer gives you standing height across the back, and together they turn a triangle into a room with a flat ceiling. It's the combination that gets quoted most often in Ealing.
What a Hip to Gable Costs
| Scope | Typical West London range |
|---|---|
| Hip to gable alone | £48,000 – £70,000 |
| Hip to gable with rear dormer | £58,000 – £85,000 |
| Add an en-suite | £5,000 – £9,000 |
These are estimates for West London, not quotes. What your loft actually costs depends on your roof, your access and what you put in the room — which is exactly what a survey is for.
What moves the number most: whether you add the dormer, whether there's a bathroom going in, how much of the existing landing has to be reworked for the stairs, and how the new brickwork has to be matched. On a house where the neighbour has already done theirs, matching is easier and the planning conversation is shorter.
Will You Need Planning Permission?
Often not — but the detail matters.
A hip to gable is a roof enlargement, so under permitted development it counts against a volume allowance: 40 cubic metres for a terrace house, 50 cubic metres for a semi-detached or detached house. A hip to gable with a rear dormer can get close to that ceiling, so the volume is worth calculating before the design is fixed rather than after.
Permitted development also requires that no part goes above the highest point of the existing roof, that the materials are similar in appearance to the house, that the eaves are kept and the addition set back at least 0.2 metres from them, and that any side-facing window is obscure-glazed and non-opening below 1.7 metres from the floor.
The exception that catches Ealing homeowners: Roof enlargements are not permitted development on designated land, which includes conservation areas. Ealing has 30 of them, and six carry Article 4 directions that remove householder rights further. If you're in one, this conversion needs full planning permission — which doesn't mean refusal, just an application.
Building regulations approval is required either way. It's a separate consent from planning and it applies even when no planning permission is needed at all.
Hip to Gable Questions
Does a hip to gable change how the house looks from the street?
Yes — the side of the roof becomes a flat wall. On streets where several houses have already done it the change reads as normal; on an unaltered street it's more noticeable, and that's usually what a planning officer is weighing.
Can I do a hip to gable on a mid-terrace?
No. A mid-terrace has no hip to fill in. Look at a rear dormer or, if you have a rear outrigger, an L-shaped dormer.
Do I need a party wall agreement?
Usually yes on a semi or end-terrace, because the work involves the shared wall. Notice has to be served at least two months before work starts, and your neighbour has 14 days to consent — if they don't reply, that counts as dissent and a surveyor gets appointed.
Find Out What a Hip to Gable Would Cost
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