Dormer vs Hip-to-Gable vs Mansard vs Velux Loft: Which Suits Your London House?
The right loft conversion for your London house is mostly dictated by the roof you already have. A terraced Victorian, a 1930s semi and a detached suburban home each lend themselves to different solutions. Below we compare the four main types, dormer, hip-to-gable, mansard and Velux, so you can see which is likely to suit your property before you speak to a builder.
The four main options
Velux (rooflight) conversion
This is the simplest option. The existing roof structure stays largely as it is, with rooflights fitted into the slope, a new floor and insulation, and a staircase below.
Best for: houses with good existing headroom, typically larger pitched roofs.
Pros: least structural change, usually the quickest to build, and often the most straightforward on planning.
Cons: you get no extra headroom or floor area, so sloping ceilings limit where you can stand and put furniture.
If your roof has good height, a Velux loft can be a cost-conscious way to gain a bedroom or office.
Dormer conversion
A dormer is a box-like structure projecting from the roof slope, most commonly at the rear. It increases both floor area and headroom, which is why it is one of the most popular loft types across London.
Best for: terraced, semi-detached and detached houses where the rear roof slope is not visible from the street.
Pros: big gain in usable space, room for a proper bathroom, and generous window area.
Cons: the flat-roofed box is not to everyone's taste, and larger dormers may have planning implications depending on your property and location.
On many Victorian terraces with a rear outrigger, an L-shaped dormer makes the most of the roof and can give you two rooms.
Hip-to-gable conversion
Many semi-detached and end-of-terrace houses have a roof that slopes inwards at the side, called a hip. A hip-to-gable conversion replaces that sloping end with a vertical gable wall, creating more volume inside. It is often combined with a rear dormer.
Best for: semis, end-of-terrace and detached houses with a hipped side.
Pros: significantly more headroom and floor area, often enough for a second bedroom plus bathroom.
Cons: it changes the look of the side of the house, involves more brickwork and structural work, and can raise planning questions.
Mansard conversion
A mansard changes the roof slope on one or both sides to a steep, near-vertical angle, usually with dormer windows set into it. It maximises space, giving you something close to a full extra storey.
Best for: terraced houses in London, where mansards are a familiar sight, and properties where maximum space is the aim.
Pros: the largest gain in space and headroom, and a style that suits many period streets.
Cons: it involves the most structural work, usually requires planning permission, and normally sits at the higher end of loft budgets.
How to choose
Start with these questions:
How much headroom do you have at the highest point of the existing roof?
Is your roof hipped, gabled or a butterfly shape?
Does the house sit in a conservation area, or is it a flat or maisonette? Permitted development rules are different or unavailable in those cases.
How many rooms do you need: one bedroom, or a bedroom and bathroom?
What are your neighbours' lofts like? Local precedent can help with planning.
A site survey is the only reliable way to confirm what will work. Our team can measure up, talk through options and explain the practical trade-offs. You can read about what we do on our loft conversions page.
Think about the street as well as the house
Roof shape is only part of the picture. Look at what neighbours have done, how visible your roof is from the road and whether your street has a consistent character. A rear dormer on a terrace is usually discreet, whereas a side or front change is far more noticeable. Councils tend to look more favourably on schemes that sit comfortably with the surroundings, so a quick walk around your area is time well spent.
It also helps to think about how the new space will be used. A single bedroom with storage needs far less volume than a bedroom, shower room and study area, and being honest about that early can save you from paying for a bigger structure than you need.
Frequently asked questions
Which loft conversion adds the most space?
Generally a mansard or a hip-to-gable with a rear dormer will add the most usable space, but the best answer depends on your existing roof.
Which is cheapest?
A Velux conversion is typically the least involved, although the cost of any loft depends on size, specification and access. Our cost calculator can give an early ballpark.
Will I need planning permission?
It varies with the conversion type and where you live. Many dormer and hip-to-gable lofts can fall under permitted development, but mansards and homes in conservation areas often need permission. Check with your local council before you commit.
Planning your loft with TNK
With 17+ years' experience and over 150 projects, we can help you decide which style fits your home and how to fit it into your budget. Contact us to arrange a visit and talk through your options.
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