The short answer
Often yes, though the rules decide how. A hip roof slopes back on every side, while a gable carries a vertical triangle of wall at the end. On many houses the conversion falls under Class B permitted development, capped at 40 cubic metres for a terrace and 50 cubic metres otherwise. It is not permitted on article 2(3) land, and Building Regulations apply whatever the planning answer.
Turning a sloping hip end into a vertical gable adds roof space, usually for a loft conversion. It alters the structure, so the planning and building checks both matter.
What a hip-to-gable conversion involves
On a hipped roof the end slopes back towards the top. The angled edge where two slopes meet is called the hip. To convert, the hip is removed and the end wall is built upwards into a gable, a triangle of masonry rising to the highest point. The roof gains floor area beneath the new end, which is why the change so often goes hand in hand with a loft conversion.
Is it a roofer's job or a builder's?
It is both trades. The roofer strips the hip, forms the new roof planes and re-covers them, while the brickwork for the gable end, the new framing and the support below call for a builder or an engineer's design. Our page on when a new roof needs a structural engineer explains the usual route.
The covering matters too. A gable brings in a verge, where the roof slope meets the gable wall, and a dry verge system can be fitted along it. We inspect and photograph the existing slopes first, then pass our findings to whoever draws the design. The wider roof replacement hub sets this change in context.
Class B and the volume limits
Class B is the part of the permitted development order for roof additions to a house. The volume limits are 40 cubic metres in the case of a terrace house and 50 cubic metres otherwise. Your designer measures the enlargement against whichever applies to your house, and the drawings should show the sum.
Does the hip face the road?
That matters. Class B does not permit an extension beyond a roof slope that forms the principal elevation of the house and fronts a highway. A hip on the side or the back is treated differently from one on the front slope facing the street, and your plans need to show which is which.
What about flats?
Flats are not dwellinghouses in the order's terms, whether a whole block or one flat inside it. A house split into flats needs a planning conversation instead.
Other conditions and limits sit within Class B as well, so ask Somerset Council's planning team to confirm your plan fits before you commission drawings or order materials. That one conversation can save a refused scheme.
Where permitted development does not apply
Class B is not available if the house stands on article 2(3) land. That land takes in conservation areas, areas of outstanding natural beauty and National Parks. Around Taunton it brings in the Quantock Hills, Blackdown Hills and Mendip Hills National Landscapes (the new name for those areas), Exmoor National Park, and the town's conservation areas.
What does that mean in practice?
On that land a hip-to-gable conversion needs a planning application. Inside Exmoor, applications go to Exmoor National Park Authority, never to Somerset Council. Elsewhere in the county, Somerset Council's planning team handles it.
What about a listed building?
A listed house keeps its Class B permitted development rights, but it also needs listed building consent for works touching its special character. Changing the shape of a listed roof is very likely to do so. Applications go to the council, or to Exmoor National Park Authority inside the Park.
Check your address on the council's planning pages, or call the team, before you spend on drawings. A short call is cheaper than a refused application, and it tells you whether the route is a permitted-development check or a full application.
Building Regulations and the neighbours
Permitted development is a planning answer. Building Regulations are a separate set of rules, and a hip-to-gable conversion falls inside them because it alters the roof structure. Speak to your building control body before work starts. In Somerset that is Somerset Building Control on 0300 303 7790, which works for Somerset Council throughout Taunton and the wider county.
Does the new roof need to be insulated?
Yes. Approved Document L (2021 edition), Table 4.2, sets a U-value of 0.15 for roof elements newly built onto existing homes. Where you are also converting the loft, other parts of the roof fall under Table 4.3. Your designer sorts the build-up out with building control.
What about the neighbour next door?
On a semi or terrace, the new gable wall may sit on or beside a party wall. A party wall surveyor, not building control, answers those questions, and the Party Wall etc. Act 1996 sets a two-month notice period for certain work. Read re-roofing for a loft conversion next, then book a look at the roof you have now.
More on changing a hip to a gable
Can a hip-to-gable conversion be done on a terrace?
A terrace has a lower Class B limit of 40 cubic metres, set against 50 cubic metres for other houses, and the party wall brings a neighbour into the question. A survey of the roof comes before any drawing, and Somerset Council's planning team can check your plan against it.
Do I need a structural engineer for the work?
In practice, yes. Removing a hip moves load onto walls and timbers that were not carrying it, and building control will expect a design showing how that load is carried. Ask an engineer to design the structure, then give the plans to your roofer to price the roof work.
The full picture: Roof replacement and new roofs in Taunton ยท More short answers