Hip to Gable Loft Conversion
A hip to gable loft conversion changes the sloped end of a hipped roof into a flat vertical wall, called a gable. Houses with a hipped roof, where all sides slope inward towards the middle rather than having a flat end wall, often lose a lot of usable loft space along that sloped side. Straightening it out into a gable wall adds real floor space and head height exactly where it is needed most.
This type of conversion is usually only possible on semi detached and detached houses, since mid terrace houses do not have a hipped end to alter in the first place. It is often combined with a rear dormer on the same project, since together they make the most of the roof space available without needing full planning permission in most cases.
Because the work changes the shape of the roof, a structural engineer will need to assess how the new gable wall is supported, and the roof covering will need to match the rest of the house so the change looks like a natural part of the property rather than an obvious addition.
Who this for
This service suits semi detached and detached houses with a hipped roof, which is common on many 1930s and postwar homes across London. It works particularly well when combined with a rear dormer, giving a good sized new room without the scale of work needed for a mansard.
Hip to Gable Loft Conversion Cost
A hip to gable conversion generally costs between £1,500 and £2,500 per square metre, though simpler finishes can come in as low as £1,300 per square metre. For a full project, most homeowners in the UK are paying somewhere between £45,000 and £75,000, with £60,000 a fairly typical figure for a 30 square metre loft space. If you are combining the hip to gable with a rear dormer, which this page already mentions is one of the most common pairings, expect the total to sit higher, usually between £60,000 and £85,000, since you are effectively getting two pieces of structural work done at once. As with most of London, prices here tend to run above the UK average, often by 20 to 30 percent, so it is worth budgeting towards the upper end of these ranges rather than the lower one. One thing worth setting aside from the start is a contingency, usually around 10 percent of the build cost. Since the roof structure is being altered, older houses sometimes reveal problems once the roof is opened up that were not visible during the survey, and it is better to have that money ready than to be caught out partway through. As always, these figures are a starting point, not a quote. The real number depends on your roof, your house, and what you want the finished room to do, which is exactly what a free survey is for.
Project Process Steps
We survey the existing hipped roof and confirm whether the property qualifies for permitted development or whether a planning application will be needed.
Our structural engineer designs how the new gable wall will be built and supported, since this replaces part of the original roof structure.
The hipped side is rebuilt as a vertical gable wall, matching the existing roof covering and brickwork so the change blends in with the rest of the house.
Once the new structure is weathertight, we complete the interior work, including insulation, plumbing, electrics, staircase and finishing.
Frequently asked questions (FAQ)
Is a hip to gable loft conversion allowed without planning permission?
In most cases, yes. Hip to gable conversions are generally covered by permitted development on semi detached and detached houses, provided the work stays within the volume limits and does not extend beyond the highest point of the existing roof. It is worth noting this option is not usually available to mid terrace houses, since they do not have a hipped end to convert in the first place.
What happens if my house is on a corner plot?
Corner plots need extra care. If the new gable wall would face a road, this can count as the principal elevation, and some councils have refused permitted development on these grounds even when the size limits are met. If you are on a corner plot, it is worth getting a Lawful Development Certificate application in early, or asking your council directly, rather than assuming the standard rule applies.
Can I combine a hip to gable conversion with a rear dormer?
Yes, this is one of the most common combinations, since straightening the hipped side gives you more room to fit a decent sized rear dormer as well. Just remember that both elements together still need to fit within your overall volume allowance.
Can bungalows have a hip to gable conversion?
Yes, though it needs extra care. Bungalow lofts were not always built to take the extra weight or provide the head height a proper room needs, so a structural engineer should check the roof carefully before you commit to a hip to gable design on a bungalow.