If we’ve got a semi detached or detached house in West London with a hipped roof, a hip to gable conversion is probably the best way to maximize your loft space. This type of conversion transforms the sloping side of your roof into a vertical gable wall, dramatically increasing the usable floor area and creating a much more practical room.
We’ve been doing hip to gable conversions across Ealing, Hounslow, Richmond, and Hillingdon for over 25 years, and they’re particularly common on 1930s semi detached properties that dominate many West London streets. These houses were built with hipped roofs that look attractive from the outside but waste loads of potential space inside. A hip to gable conversion unlocks that space and transforms your loft from an awkward, cramped area into a proper bedroom or home office.
Let us walk you through everything you need to know about hip to gable conversions: what they are, what they cost, whether one would work for your property, and how to get the best results.
What Is a Hip to Gable Conversion?
A hip to gable conversion involves replacing the sloping side of your roof (the hip) with a vertical wall (the gable). This creates a much larger internal space because you’re replacing a sloping surface that eats into your usable floor area with a vertical wall that provides full head height right to the edge of the room.
Most hip to gable conversions also include a rear dormer, which extends out from the back of the property to create even more space. The combination of hip to gable plus rear dormer is extremely effective and provides significantly more usable floor area than either element alone.
To understand why this works, picture a typical hipped roof. You’ve got a main ridge running front to back, with the roof sloping down on all four sides. The two side slopes (the hips) angle down from the ridge to the eaves, creating triangular sections at the sides of the loft. These sloping sides waste loads of potential space.
When we do a hip to gable conversion, we remove one of those sloping sides (usually the side that doesn’t adjoin your neighbour on a semi detached property) and replace it with a vertical gable wall. This instantly creates more usable space because you’ve got a vertical wall instead of a sloping roof.
Then we typically add a flat roof dormer across the rear, which projects out from the back of the property and creates even more space. The combination gives you a loft room with good head height throughout and enough space for a proper bedroom with ensuite, or a large home office.
Why Hip to Gable Conversions Work Well in West London
West London has thousands of semi detached and detached properties with hipped roofs, particularly 1930s houses in areas like Ealing, Greenford, Northolt, Ruislip, Hanwell, Hounslow, and parts of Richmond. These properties are perfect candidates for hip to gable conversions.
The 1930s semi detached house is a West London staple. These properties typically have three bedrooms, and as families grow, that third bedroom often gets converted into a home office or playroom, leaving the family short of bedroom space. A hip to gable conversion creates a fourth bedroom without the cost and disruption of a ground floor extension.
Planning permission for hip to gable conversions is generally straightforward in West London, provided you’re not in a conservation area. Most hip to gable conversions fall within permitted development rights or require only straightforward planning applications.
The cost effectiveness is excellent. Hip to gable conversions typically cost £50,000–65,000, which is more than a basic dormer but less than a mansard. You get significantly more space than a simple dormer conversion, making the extra investment worthwhile.
The value added is strong as well. Adding a fourth bedroom to a three bedroom semi detached house in West London can add 15–20% to your property’s value, often more if you create a master suite with ensuite bathroom.
Hip to Gable vs Standard Dormer Conversions
The key difference between a hip to gable conversion and a standard dormer conversion is the amount of usable space you gain.
A standard dormer on a hipped roof property extends out from the rear but leaves the hipped sides in place. You gain some space from the dormer, but the sloping hips still eat into your usable floor area on both sides of the room.
A hip to gable conversion removes one of those sloping sides entirely, replacing it with a vertical wall. This creates significantly more usable space, typically 20–30% more floor area than a standard dormer alone.
The combination of hip to gable plus rear dormer is extremely effective. You’ve got a vertical wall on one side (from the hip to gable), a vertical wall at the rear (from the dormer), and only one remaining sloping side (the hip that adjoins your neighbour). This creates a much more practical room shape with good usable space throughout.
The cost difference is £5,000–10,000 more for a hip to gable conversion compared to a standard dormer. Given the significant increase in usable space, most clients find this extra investment worthwhile.
Planning Permission for Hip to Gable Conversions
Permitted Development
Many hip to gable conversions fall within permitted development rights, meaning you don’t need planning permission. The key criteria are that the volume of space added doesn’t exceed 50 cubic metres (for detached and semi detached houses), the highest point of the conversion is no higher than the highest point of your existing roof, materials are similar in appearance to your existing property, and you’re not in a conservation area, Area of Outstanding Natural Beauty, or other designated area.
If your conversion meets these criteria, you can proceed under permitted development, though you’ll still need building regulations approval.
When Planning Permission Is Required
Planning permission is required if you exceed the 50 cubic metre limit (which is possible on larger properties with extensive conversions), you’re in a conservation area or other designated area, your property is listed, or you’re proposing to go higher than your existing roof ridge.
Even when planning permission is required, hip to gable conversions are generally well received by West London planning authorities. They’re a common and accepted form of development that doesn’t dramatically alter the character of residential areas.
Party Wall Agreements
If you’re doing a hip to gable conversion on a semi detached property, you’ll need a party wall agreement with your neighbour because the work affects the party wall between your properties.
This is a legal requirement under the Party Wall Act. You must serve notice on your neighbour at least two months before work begins, and if they dissent (or don’t respond), you’ll need to appoint a party wall surveyor to prepare an award.
Party wall agreements typically cost £700–1,500 and take 2–3 months to complete. We advise on the party wall process and can recommend experienced party wall surveyors.
Most neighbours are reasonable about party wall agreements, particularly if you explain the work clearly and address any concerns. The party wall process protects both parties and ensures any damage is properly documented and rectified.
The Construction Process
Hip to gable conversions involve more structural work than standard dormer conversions because you’re removing and rebuilding a significant section of your roof.
Timeline
Construction typically takes 12–16 weeks for a hip to gable conversion with rear dormer. This is longer than a standard dormer (10–14 weeks) because of the additional structural work involved in removing the hip and building the gable wall.
Including design, planning (if required), party wall agreements, and building regulations approval, the total timeline is 5–7 months from initial consultation to completion.
What’s Involved
We start by erecting scaffolding around the relevant side and rear of your property. This provides safe access for the extensive roof work.
The existing hipped section of roof is carefully removed. This is precision work; we remove only the section that needs to be replaced while keeping the rest of your roof intact and weatherproof.
A new gable wall is built where the hip used to be. This is typically a timber frame wall that’s clad to match your existing property. The wall must be perfectly vertical and properly tied into your existing structure.
Steel beams are installed to support the new roof structure and create open space inside without internal supporting walls. Hip to gable conversions typically require substantial steelwork because you’re creating a large open space.
The rear dormer is built, extending out from the back of the property. This is constructed with a timber frame, clad to match your property, and fitted with windows.
Floor joists are installed or strengthened to create a solid floor that meets building regulations load requirements.
The staircase is installed, connecting your new loft space to the floor below. Finding space for the staircase is often one of the biggest challenges in hip to gable conversions.
Internal work includes insulation throughout (roof, floor, walls), electrical wiring for lights, sockets, and heating, plumbing if you’re having an ensuite bathroom, plasterboarding and plastering, and all finishing work (decoration, flooring, doors, fixtures).
Building control inspects at key stages and issues your completion certificate once everything is complete and compliant.
Cost of Hip to Gable Loft Conversions in West London
Hip to gable conversions typically cost £50,000–65,000 in West London, depending on property size and specification.
Basic Hip to Gable Conversion: £50,000–55,000
This includes removing the hipped section and building the new gable wall, rear dormer construction, substantial steelwork to support the new structure, new floor joists and flooring, full insulation to building regulations standards, new staircase, electrical work (lighting, sockets, heating), plastering and decorating, and standard flooring throughout.
This creates a large, usable loft room suitable for a bedroom or home office.
Hip to Gable with Ensuite: £55,000–65,000
Adding an ensuite bathroom increases the cost by £8,000–12,000 depending on fittings quality. This includes all plumbing work, bathroom suite, tiling, and fixtures. Many clients doing hip to gable conversions include an ensuite because the space allows for a proper master suite.
Premium Hip to Gable Conversion: £60,000–75,000+
High-end finishes and features increase costs. This might include underfloor heating throughout, luxury bathroom fixtures and fittings, hardwood flooring, extensive custom joinery and built-in wardrobes, designer lighting and electrical fixtures, and high specification windows.
What Affects the Cost
- Property size – Larger properties have bigger roof sections to remove and rebuild, increasing material and labour costs.
- Extent of steelwork – Substantial steel beams are typically needed; size and number affect cost significantly.
- Staircase location and design – If we can build the staircase above existing stairs, costs are lower. More complex locations increase costs.
- Party wall agreements – Add £700–1,500 to the total cost.
- Planning permission (if required) – Application fees (£206) plus architectural drawings (£2,000–3,000).
At Loft Conversion West London, we provide fixed price quotes that include all these elements, so you know exactly what you’re paying.
Design Considerations for Hip to Gable Conversions
Good design maximises the space gained from a hip to gable conversion and creates a comfortable, attractive room.
Gable Wall Design
The new gable wall must match your existing property’s appearance. We typically clad it with render, brick, or tile hanging to match your existing walls.
The gable wall must be properly proportioned. A gable that’s too large or poorly designed looks out of place and may be refused planning permission if you’re in an area where permission is required.
Windows in the gable wall provide additional light and ventilation. We typically install one or two windows in the gable, positioned to provide good light without creating overlooking issues for neighbours.
Dormer Design
The rear dormer should be proportionate and well designed. Planning authorities and permitted development rules typically require that dormers are set back from the eaves, set in from the sides of the roof, and don’t extend higher than the existing ridge.
Window design matters. Multiple smaller windows often look better than one large window, and they provide better ventilation options.
Materials should match or complement your existing property. Flat roof dormers are typically clad with tile hanging, render, or weatherboarding to match your house.
Internal Layout
The generous space created by a hip to gable conversion allows for flexible layouts. The most popular option is a master bedroom suite with ensuite bathroom, walk-in wardrobe or dressing area, and good storage.
Alternatively, you could create a large bedroom plus a separate home office, or even two smaller bedrooms if your property is large enough.
The gable wall provides a full height vertical surface that’s perfect for positioning beds, wardrobes, or desks. You don’t have to worry about sloping ceilings in this area.
The remaining hipped side (the one adjoining your neighbour) still has a sloping ceiling, but with the gable wall on the other side and the dormer at the rear, you’ve got plenty of usable space with good head height.
Storage Solutions
Built-in storage in the remaining eaves area (under the hipped side that adjoins your neighbour) makes excellent use of space that would otherwise be awkward. Wardrobes, drawers, and shelving fitted into these areas provide loads of storage while keeping the main room space clear.
The gable wall side has full head height right to the edge, so you can use standard freestanding furniture without worrying about sloping ceilings.
Living with a Hip to Gable Loft Conversion
Space and Practicality
Hip to gable conversions create genuinely practical rooms with good usable space throughout. The combination of the vertical gable wall, the rear dormer, and only one remaining sloping side means you’ve got far more usable floor area than with a standard dormer conversion.
You can position furniture anywhere without constantly worrying about head height. The gable wall side and the dormer area both have full head height, and only the remaining hipped side has reduced headroom.
Most clients are surprised by how spacious hip to gable conversions feel. They expect a cramped loft room and instead get a proper bedroom that feels like any other room in the house.
Natural Light
Hip to gable conversions typically have excellent natural light. Windows in the gable wall, windows in the rear dormer, and potentially Velux windows in the remaining roof sections combine to create a bright, airy space.
The multiple window positions provide light from different directions throughout the day, which creates a pleasant, well-lit room.
Temperature and Comfort
Properly insulated hip to gable conversions are comfortable year-round. Building regulations require high-performance insulation, which keeps the space warm in winter and prevents overheating in summer.
Heating is usually provided by extending your existing central heating system. Radiators positioned under windows or on the gable wall keep the space comfortable.
Good ventilation is important. Opening windows in the gable wall and dormer creates excellent cross-ventilation on warm days.
Privacy
Windows in the gable wall need careful positioning to avoid overlooking neighbours. We typically position them to provide light and views without directly overlooking neighbouring properties, or we use obscure glazing in lower sections if needed.
Rear dormer windows generally don’t create privacy issues because they face your garden rather than neighbouring properties.
Value Added by Hip to Gable Conversions
Hip to gable conversions add significant value to West London properties, typically 15–20% of your property’s value.
On a £650,000 semi detached house in Ealing or Hounslow (fairly typical for a three-bedroom 1930s semi), that’s £97,500–130,000 added value for an investment of £50,000–60,000. The return on investment is excellent.
The value added is particularly strong when you’re creating a fourth bedroom in a three-bedroom house. Four-bedroom properties command a significant premium over three-bedroom properties in the West London market.
If you create a master suite with ensuite bathroom, the value added is even greater. Properties with luxury master suites are highly desirable and achieve premium prices.
Estate agents consistently tell us that hip to gable conversions are one of the best investments you can make in a semi detached property. The conversion needs to be done well—poor quality work doesn’t add value—but a professional hip to gable conversion from a reputable company delivers excellent returns.
Frequently Asked Questions (FAQs)
How much does a hip to gable loft conversion cost in West London?
A hip to gable conversion typically costs £50,000–65,000 in West London, which is more than a standard dormer (£45,000–60,000) but provides significantly more usable space—typically 20–30% more floor area. If you include an ensuite bathroom, expect to pay £55,000–65,000. At Loft Conversion West London, we provide fixed price quotes with no hidden costs, including all structural work, the new gable wall, rear dormer, steelwork, staircase, and finishing.
Do we need planning permission for a hip to gable conversion?
Many hip to gable conversions fall within permitted development rights and don’t need planning permission, provided the volume added doesn’t exceed 50 cubic metres, you’re not in a conservation area, and the conversion doesn’t go higher than your existing roof ridge. However, you’ll always need a party wall agreement with your neighbour on a semi detached property, which takes 2–3 months and costs £700–1,500. We advise on planning and party wall requirements during our initial survey.
How long does a hip to gable loft conversion take?
Construction takes 12–16 weeks, which is longer than a standard dormer (10–14 weeks) because we’re removing the hipped section and building a new gable wall. Including design, party wall agreements, planning (if required), and building regulations approval, the total timeline is 5–7 months from initial consultation to completion. The party wall process typically accounts for 2–3 months of this timeline.
Will a hip to gable conversion work on my semi detached house?
Almost certainly yes. Hip to gable conversions are specifically designed for semi detached and detached properties with hipped roofs. We remove the hip on the side that doesn’t adjoin your neighbour (the gable end) and replace it with a vertical wall, creating significantly more usable space. This is one of the most common and effective conversion types for 1930s semi detached houses that are prevalent throughout West London.
How much space does a hip to gable conversion create?
Typically 20–30% more usable floor area than a standard dormer conversion alone. A hip to gable conversion with rear dormer on a typical West London semi detached house creates 20–30 square metres of usable floor space—enough for a master bedroom with ensuite and walk-in wardrobe, or a large bedroom plus separate home office. The vertical gable wall provides full head height right to the edge of the room, maximising usable space.
Can we have an ensuite bathroom in a hip to gable conversion?
Absolutely. Hip to gable conversions provide enough space for a comfortable ensuite bathroom alongside a good sized bedroom. We connect to your existing soil stack and water supply, install a shower pump if needed, and create a fully functional bathroom. Budget an extra £8,000–12,000 for a complete ensuite including all plumbing work and fittings. Most clients creating master suites include ensuites.
Do we need a party wall agreement for a hip to gable conversion?
Yes, if we’re doing a hip to gable conversion on a semi detached property. The work affects the party wall between your property and your neighbour’s, so you must serve notice under the Party Wall Act at least two months before work begins.
