Project: a hip-to-gable loft conversion in a Bristol semi
Stand in the road outside a 1930s semi in Henleaze, Bishopston or Fishponds and look at the roof. It has three slopes, not two. The end is hipped, sloping down towards the side wall, which looks tidy from the street and quietly steals about a third of the loft. A hip-to-gable loft conversion is the fix: we take the sloping end off, build the side wall up to the ridge as a vertical gable, extend the roof to meet it, and usually add a rear dormer for a flat back wall.
The house here is the classic Bristol semi: bay at the front, garden at the back, a hipped roof and a loft nobody had visited since the last tank change. This one is in BS9. This is how a build like it runs from first look to sign-off, and what it costs.
The semi roofline problem a hip-to-gable solves
On a hipped roof the ridge stops well short of the side wall, so the strip where you can stand up straight is narrow. A rear dormer alone does not solve it, because the hip cuts diagonally through the corner where the new stair needs to arrive. Build the gable and the ridge runs the full length of the house, the stair lands under it with proper headroom, and the dormer at the back gives you the wall the bed goes against.
Planning is usually straightforward. Semis get a 50 cubic metre allowance under permitted development, and the Planning Portal's loft conversion guidance confirms hip-to-gable work is exempt from the rule that a roof enlargement must sit 20 cm back from the eaves. Materials must look similar to the house, and a side-facing window in the new gable must be obscure-glazed and non-opening below 1.7 m. This one was different. The loft went in alongside a side extension, and that combination took it outside permitted development, so the whole scheme went in as a full planning application. Our guide to the 40 and 50 cubic metre rules explains the arithmetic; which loft conversion fits your roof shows the alternatives.
Before and after: space and light
Before: a hatch, a tank and a triangle of usable floor down the middle. After: a full-height room across the width of the house, a double bedroom with an en-suite in the loft, and a living area and kitchen in the side extension, the stair arriving under the new ridge and eaves cupboards along the low side. Light comes from the rear dormer and roof windows on the front slope; the gable, in blockwork or insulated timber frame finished to match, is solid or takes an obscure-glazed window, so nobody overlooks the neighbours. Nationwide's research, reported by Which? in October 2025, found that adding a large double bedroom and a bathroom by loft conversion or extension can add up to 24% to a three-bed, one-bath home.
[IMAGE: Team raising a timber stud frame on a scaffold deck | alt: Wilson & Cole team raising a dormer stud frame on a Bristol loft conversion] (suggested file: loft-team-raising-dormer-frame_16x9.jpg; caption: our team raising a dormer frame on a Bristol loft, not this project)
How the build ran, week by week
A hip-to-gable with a rear dormer is a 10 to 14 week programme on site for us; this one took. The shape of it:
- Before we start: the structural engineer's calculations for the steels, which bear on the party wall and the new gable. Cutting into the wall you share means a party structure notice to the neighbour two months before work under the Party Wall etc. Act 1996. Here it did not apply at all: the house is detached, so there were no party wall notices to serve. Our Party Wall Act guide covers what the notice says.
- Weeks 1 to 2: scaffold up, hip end stripped and sheeted, gable built, steels in.
- Weeks 3 to 5: ridge and rafters extended, dormer framed, felt, batten and tile, windows in. Weathertight, which is when everyone relaxes.
- Weeks 6 to 8: floor joists, insulation to Part L (0.15 W/m²K for the new roof, 0.18 for the gable wall, per the Approved Documents), studwork, first-fix plumbing and electrics, and the stair cut through, which is the noisy week.
- Weeks 9 to 12: plasterboard and skim, second fix, en-suite, decoration, building control inspections and the completion certificate.
Until the stair goes in, the loft is reached from the scaffold and the house below carries on as normal, which is why a loft is the least disruptive big build there is. We explain how we keep your home liveable during a build elsewhere, where the loft stair goes and why has the headroom rules, and how long a loft conversion takes has the full week-by-week.
What it was like to live with
An FMB verified review of one of our builds puts it better than we can: "They would begin work at 8am without fail, communicate the process to me at all times… The site was kept immaculately clean and organised. Most importantly, their attitude around the site made them a joy to have around." That is the standard on every site, and it matters most on a loft, where the family is downstairs the whole time. Dan or Craig is your point of contact from quote to sign-off.
What a hip-to-gable loft conversion costs on a Bristol semi
Our guide price for a hip-to-gable loft conversion starts at £50,000 excluding VAT, against from £40,000 for a straightforward rear dormer; our 2026 loft conversion guide prices show what moves the number. Every quote is detailed and itemised, and once you are in the diary we ask for a modest booking deposit of around 10%, never a large payment up front. If you want to see one of our loft conversions in Bristol at this stage, ask.
Frequently asked questions
Do you need planning permission for a hip-to-gable loft conversion in Bristol?
Usually not. On a semi it falls under permitted development within the 50 cubic metre allowance, provided materials look similar, side windows are obscure-glazed and the house is not in a conservation area or a flat. We recommend a lawful development certificate as proof; building regulations approval is needed regardless.
Can you do a hip-to-gable on a terraced house?
Only on an end-of-terrace, because a mid-terrace has no hip to remove. End-terraces count as terraced houses for permitted development, so the smaller 40 cubic metre allowance covers the gable and dormer combined.
How long does a hip-to-gable loft conversion take?
Ten to 14 weeks on site for a hip-to-gable with a rear dormer. Add around eight weeks for a lawful development certificate and two months' notice under the Party Wall Act before work starts, which is why we ask people to talk to us early.
Does my neighbour have to agree to a hip-to-gable?
They cannot stop it, but the Party Wall Act gives them 14 days to respond to the notice. If they dissent, or say nothing, a surveyor prepares an award that protects both sides, and the building owner normally pays the reasonable fees.
How much does a hip-to-gable loft conversion cost?
Our guide price starts at £50,000 excluding VAT for a hip-to-gable with a rear dormer on a Bristol semi, quoted detailed and itemised once we have seen the roof.
Come and see a site we're working on. That tells you more than any brochure. Tell us about your roof and we will call you back within one working day.
