The short answer
The common UK roof shapes are gable, hip, flat, mansard and lean-to, and many houses combine two or more. Shape changes the price because it changes the amount of ridge, hip, valley and edge detail to build. It changes wind exposure and repairs too. For a semi-detached house, MyBuilder's replacement ranges stretch between £2,500 and £12,000 across the shapes.
How to tell which shape you have
Start with the ends of the house. If the end wall rises straight up to a point under the ridge, that triangle of brick is a gable. If the roof slopes inward on every side, so the end of the roof is a sloping face rather than a wall, the shape is a hip. A flat roof shows no obvious slope from the road, though it is never truly level, because it needs a fall so rain can drain away.
A mansard is built with a steep lower slope under a shallower upper one on each side, which makes usable room inside the roof. Many mansards were added to a house later, so look for a flat or low-pitched top and a well-flashed junction between the two slopes. A lean-to rises from a wall and tilts one way only, as on many rear extensions and porches. Plenty of houses mix these shapes. A Victorian terrace may be gabled at the front and carry a flat roof or lean-to over a back addition, with a valley where they meet.
Mixed shapes are not a problem in themselves, but each join between them is a place a roofer will inspect closely. If you can, photograph your roof from the road and from the back garden. Two photographs from different sides show the shape more clearly than any description, and they help when you ring to describe what you have.
What each shape costs and why
MyBuilder's replacement guide, updated in August 2026, prices a semi-detached roof of 50 to 80 square metres by shape. The figures are national and typical, and they are not a quote for any particular house.
| Roof shape | Typical range for a semi |
|---|---|
| Gable | £5,000 to £8,000 |
| Hipped | £8,000 to £12,000 |
| Flat | £2,500 to £6,000 |
| Lean-to | £3,000 to £5,500 |
A hipped roof costs more since there is more of it to build: extra slopes, hip lines to cut and finish, and more edges to seal. The covering counts as much as the outline, so only a written quote after a survey gives a figure worth planning around. Hips and valleys also lengthen the job: more cuts, more lead, more time at height. A lean-to is cheaper than a hipped roof mainly because it is smaller and has fewer edges, not because the work is any easier.
Wind exposure and where each shape fails
A gable presents a flat wall to the wind, and the edge where roof meets wall is the verge. Verges lift if tiles are poorly bedded or fixed, so they deserve a look after a gale. A hipped roof slopes away from the wind on every side and often copes better in an exposed spot, though its hips are another place where tiles can work loose.
Since the 2014 revision of BS 5534, a bed of mortar is no longer trusted on its own to hold ridge and hip tiles; clips or screws add a mechanical fix. Ridge, verge and dry-fix shows how this is done in practice.
Flat roofs tend to fail at their edges, upstands and outlets, and wherever water stands. On paper a flat roof is designed to a fall of 1:40, so that the finished minimum is 1:80, as IKO explains citing BS 6229. In practice decks sag and settle, and a roof built too shallow collects puddles that age the membrane faster. Lean-tos give trouble at the abutment, the point at which the slope abuts the house wall, with flashing doing the sealing.
Valleys, dormers and the joins between shapes
Where two shapes meet you get a valley, and a valley carries more water per metre than any open slope. A back addition on a terrace, a bay window roof or a dormer cheek all create joins that need lead or a lined trough. On a mixed roof, leaks tend to start at those joins rather than in the open slope.
For the cost and causes, see how much it costs to repair a roof valley. Dormers add small valleys and soakers, the folded pieces of lead that seal the side of the dormer to the main slope. The page on Swindon's houses and their roofs shows which shapes turn up on which kinds of house.
Changing a roof's shape is not re-covering it
Swapping tiles for tiles is one thing. Turning a hip into a gable, adding a dormer or raising a ridge changes the outline, and that is a different matter for planning and building control. Whether you need consent depends on the work and on where the house stands. In a conservation area or a National Landscape the rules change again, and roof work in the North Wessex Downs and Cotswolds explains how.
For pitched shapes in more depth, including mansards and lean-tos, the guide to pitched roof types goes further than this page does.
What the shape tells us at the survey
On a survey the shape sets our checklist. A gable means verges and barge boards. A hip means hip tiles and the iron bracket at the foot of each one. A flat roof means falls, edges and outlets. A mixed roof means every join. Photographs of each part come to you with the written quote at Skyline Swindon Roofing, and we propose the minimum work that actually cures the problem.
The covering also governs how long a roof lasts; our table of roof lifespans sets that out, and if any word here was new, the roofing terms glossary explains it. Our workmanship is guaranteed in writing for 10 years.