Converting your loft adds valuable living space without expanding your footprint, but picking the right type can make or break your project. The three most common loft conversions are dormer, mansard, and hip to gable.
Dormer means a boxy extension that sticks out from your roof, giving you more headroom and floor space. Mansard is the big one—a new, nearly vertical wall at the back, which gives you the most space.
Hip to gable stretches a sloped roof end into a straight, vertical wall. Each has its place, so knowing the differences is pretty important before you start.
Dormer conversions suit most homes and usually don’t need planning permission. Mansard conversions offer the most space but cost more and generally require approval.
Hip to gable works best if you’ve got a semi-detached or detached house with a hipped roof. Your roof shape, your budget, and the space you want all play a role in which style will actually work for you.
Key Takeaways
- Dormer, mansard, and hip to gable are the main loft conversion types, each offering different amounts of space and needing different levels of work.
- Your roof structure and whether you need planning permission will decide which conversion type you can go for.
- Costs range from around £50,000 to £69,000. Dormers are cheaper; mansards add the most value.
Understanding Key Loft Conversion Types
Dormer, mansard, and hip to gable conversions all change your roof structure to give you more living space. They each have their own construction quirks, costs, and space gains.
Dormer Loft Conversion Overview
A dormer loft conversion adds a boxy bit that juts out vertically from your existing roof slope. This creates a flat roof section with vertical walls, so you get proper headroom and a room that feels like, well, a room.
Types of dormer conversions:
- Flat roof dormer – stretches across the full width at the back.
- Side dormer – pops out from the side slope.
- Front pitched dormer – smaller, with an angled roof.
- L-shaped dormer – two dormers joined together, making an L.
You can put normal vertical windows in the dormer walls, facing outward for light and a view. Most dormer conversions fall under permitted development, but it’s always smart to check with your local council.
Dormers usually fit most roof types and can add up to 50 cubic metres of extra space. Costs start from £55,000, so they’re more affordable than mansards but still offer a lot of usable floor area.
Mansard Loft Conversion Overview
A mansard conversion gives you the most space by swapping out one or both roof slopes for a near-vertical wall (about 72 degrees). The new roof on top is nearly flat, and the steep walls give you loads of headroom.
Usually, people build a mansard at the back of the house, but you can do a double mansard on both sides if you really want to go big. Windows sit in little box dormers that poke out from the steep wall, letting in plenty of light.
Mansards work on pretty much any property, even terraced houses where other options might not fit. These big changes almost always need full planning permission.
Mansard conversions start at £69,000, making them the pricier choice. But you get a huge chunk of usable space—sometimes it feels like a whole new floor.
Hip to Gable Loft Conversion Overview
A hip to gable conversion changes a hipped roof (all sides sloping down) into a gable end with a straight, vertical wall. This creates a triangular wall that adds both height and floor space.
The process involves extending the roof slope on one side to meet a new vertical gable wall. You end up with way more headroom and usable floor area than before.
You can even combine this with a dormer for even more space. Hip to gable works for semi-detached and detached homes but not for terraced houses with shared roofs.
This one takes more structural work than a basic dormer, with costs starting from £60,000. Sometimes you can do it under permitted development, but the extra changes might mean you’ll need planning permission.
Dormer Loft Conversion Types
Dormer loft conversions come in four main styles, each adding floor space in its own way. The right one depends on your roof, how much space you want, and whether you’re adding to the front, side, or back.
Flat Roof Dormer
Flat roof dormers are everywhere in the UK. They’re boxy, have a flat roof, and usually run along the back of the house.
This design gives you the most headroom and floor space inside. You get a proper rectangle of a room with vertical walls.
Most rear dormer extensions with flat roofs don’t need planning permission if they stay within certain limits. The dormer usually sits below the main roof’s ridge line. You can fit regular windows along the front for loads of daylight.
Flat roof dormers are great for adding bedrooms, bathrooms, or a home office. The straightforward build keeps costs down compared to more complex conversions.
Pitched Dormer
Pitched dormers have a sloped roof, matching your main roof or sometimes at a gentler angle. They’re smaller and often used on the front of houses where planning is stricter.
You’ll spot pitched dormers on period homes and in conservation areas. They look more traditional, which keeps planners happy.
The sloped roof means you get less usable floor space compared to a flat roof dormer, and some spots inside will have lower headroom. But they’re more likely to get planning approval where looks matter.
Front-facing pitched dormers almost always need planning permission. They’re a solid pick if you want a bit of extra room without messing with your home’s character.
L-Shaped Dormer
L-shaped dormers join two dormers together to make extra floor space across two roof sections. Usually, this means a rear dormer joined to a side dormer, forming an L from above.
This setup gives you the most space without going full mansard. You can fit two rooms or a big open-plan area—ideal for a main bedroom with an en-suite.
L-shaped dormers cost more than a single flat roof dormer because of the extra work and materials. Building regs get a bit more complicated too.
The side bit of an L-shaped dormer might need planning permission even if the rear one doesn’t. Always check with your local council before you start.
Side Dormer
A side dormer sticks out from the side slope instead of the front or back. It’s handy for homes where the roof ridge runs front to back. Semi-detached and detached houses often go for this style.
Side dormers add width to your loft space, making vertical walls where you had sloped ceilings. That extra floor area means you can actually fit furniture and move around.
You’ll probably need planning permission for a side dormer since it changes the side view of your house. On corner or detached properties, it might be visible from the street or your neighbour’s window.
Pairing a side dormer with a rear dormer can really open up your loft, giving you that L-shaped layout and tons of usable space.
Mansard Loft Conversions in Detail
A mansard loft conversion gives you the most usable space of any style. The nearly vertical back wall and flat roof mean you get a full-height room almost everywhere.
Classic Mansard Design Features
A mansard roof has a back wall built at 72 degrees, so it’s nearly vertical. This steep angle maximises floor space and headroom.
The flat roof sits right on top of the angled wall. Most mansards go at the back of the house. You’ll see boxy dormers poking out of the wall for windows and extra light.
This build needs a lot of brickwork to match the rest of your house. Builders use proper insulation and waterproofing for the new wall and roof.
You can fit big bedrooms with loads of standing room. Most people add an en-suite bathroom and don’t feel cramped. With all that headroom, sloping ceilings are basically a non-issue.
Double Mansard Conversions
A double mansard puts this type of conversion on both the front and back of your house. It basically gives you a whole new floor, not just a loft.
This works well for terraced houses where you want as much space as possible. The cost goes up a lot—you’re building two mansards, after all. But your property value jumps with the extra square footage.
Planning permission gets trickier with a double mansard. Changing the front of your house means more scrutiny from the council.
Planning Permission for Mansard Conversions
You pretty much always need full planning permission for a mansard loft. The scale of the work goes way beyond permitted development.
You’ll need to submit architectural drawings and details about materials. The new brickwork should match your house, and windows and roofing need approval too.
Expect planning decisions to take about eight weeks. Some councils might ask for design tweaks to fit the neighbourhood. If you’re in a conservation area or your house is listed, expect even more hoops to jump through.
Hip to Gable Loft Conversions Explained
A hip to gable conversion changes a sloped side of your roof into a vertical wall, giving you more usable loft space. This style works best for certain homes and can add at least 20 square metres of floor area.
Process and Main Benefits
A hip to gable conversion straightens out the hipped end of your roof by building a new vertical gable wall. The process means removing the angled hip and putting up a straight wall that matches the rest of your house.
This opens up at least 20 square metres of new floor space. You get about 2 metres more headroom, making the loft way more practical.
The work can boost your home’s value by 10-20%. You can squeeze in an extra bedroom, home office, or playroom—no need to sacrifice the garden.
Key advantages:
- Bigger windows mean more natural light.
- Loads more headroom.
- You keep all your outdoor space.
- Often allowed under permitted development.
You can also upgrade insulation and fit energy-efficient windows, which helps keep heat in and could save you £240–£445 a year on energy bills.
Suitability for Different Property Types
Hip to gable conversions really shine for detached homes, semi-detached houses, and end-of-terrace properties. For this type of conversion, your roof should have at least three pitches.
Detached houses can get hip to gable conversions on both ends. Semi-detached homes usually convert just one hipped side, since the other side connects to your neighbour.
End-of-terrace properties can convert the gable end that doesn’t join another house. For these properties, the conversion needs to stay within 40 cubic metres of new space under permitted development.
Property types where this works:
- Detached houses (both ends)
- Semi-detached houses (one side)
- End-of-terrace homes (exposed end)
- Some bungalows if the roof’s tall enough
Terraced homes in the middle of a row don’t work for hip to gable conversions. Both sides connect to neighbours, so you’ll need a different style.
Your hipped roof should have enough pitch and height for usable space. A structural engineer can check if your roof will support the changes.
Hip to Gable with Rear Dormer
Pairing a hip to gable with a rear dormer gives you the most space possible. The hip gets extended vertically to form your gable wall, and a dormer pops out from the rear slope.
This combo works great when a basic hip to gable doesn’t give you enough headroom or floor area. The dormer brings extra height and space where your roof’s pitch limits things.
A rear dormer blends into your hip to gable conversion, so the loft feels like one big, continuous space. You get more standing room throughout, not just near the gable.
The dormer usually stretches along most of your rear roof. It’s a super common style because it maximises floor space and head height.
Combined benefits:
- More floor area from both features
- Better headroom throughout the loft
- Flexible room layout options
- Usually covered by permitted development
Since the dormer sits at the back, it’s less visible from the street. Your home’s look stays pretty much the same, but you gain a lot of space inside.
Other Popular Loft Conversion Styles
There are loads of loft conversion styles beyond dormer, mansard, and hip-to-gable. Velux and rooflight options are affordable, modular systems are speedy, and L-shaped designs squeeze out extra space in tricky roofs.
Velux and Rooflight Conversions
A Velux or rooflight conversion is probably the simplest way to convert your loft. You don’t mess with the roof structure—just fit windows into the existing slope.
This works best if your loft already has enough headroom and floor space. Velux conversions usually start from £50,000, so they’re the cheapest option.
Key advantages:
- Usually no planning permission needed
- Minimal disruption to daily life
- Fast build time—often 4-6 weeks
- Lower structural costs
The catch? Rooflight conversions don’t add headroom. You’re working with what you’ve got, so sloped ceilings stick around. These are best for home offices, spare bedrooms, or hobby spaces—not really for big, full-height rooms.
Your roof needs enough pitch, and the joists have to support the conversion. Trussed roofs might need extra structural work, which bumps up the cost.
Modular and Bespoke Solutions
A modular loft conversion means your whole roof comes off and gets replaced with a prefabricated structure made off-site. The new module arrives with walls, floors, a roof, and sometimes even electrics and plumbing.
Expect to pay from £53,000 for this style. The entire module gets craned into place in a day or two, though there’s prep work before that.
You get fixed pricing upfront, so there aren’t any surprise costs. Build quality is usually high since the modules are made in factories.
Modular conversions work for you if:
- You want a guaranteed completion date
- You hate on-site disruption
- You need lots of extra space (basically a whole new floor)
- Your property has access for delivery lorries and a crane
Downsides? You’ll need planning permission, and you don’t get as much design flexibility as with traditional builds. Make sure your street can handle big vehicles and a crane.
L-Shaped Loft Conversion Applications
An L-shaped loft conversion connects two dormers at right angles, giving you way more space than a single dormer. This setup is great for homes where you need to work around odd features or max out your floor area.
L-shaped conversions are especially handy on corner properties or houses with complex roof layouts. The two dormers spread out the headroom and let you play around with room layouts.
They’re pricier than standard dormers because you’re building two structures that need to fit together seamlessly.
L-shaped conversions are perfect when you want multiple rooms in your loft—like an en-suite bedroom and a separate bathroom. The perpendicular dormers bring in light from two sides, making spaces feel brighter and more open.
Key Considerations Before Choosing a Loft Conversion
Before you start messing with your loft, check if your property is even suitable. You’ll need to understand the structure and what permissions you’ll need. These things will affect which conversion you can do and how much you’ll spend.
Assessing Loft Space and Head Height
Your loft needs to meet some minimums. You want at least 2.2 metres of headroom from the floor to the highest part of the roof. That measurement decides if you can do a simple conversion or if you’ll need more serious work.
Measure from the top of your ceiling joists to the ridge. If you don’t have enough headroom, you can either lower the ceiling in the room below or raise the roof. Lowering the ceiling is cheaper, but you’ll lose space downstairs. Raising the roof is more complicated and costs more.
The roof structure matters a lot too. Traditional cut roofs with individual rafters are much easier to convert than modern truss roofs. Truss roofs need a structural engineer to design new supports, which adds to the cost and hassle.
Building Regulations and Structural Work
Every loft conversion has to meet building regulations, even if you don’t need planning permission. These rules cover fire safety, structure, insulation, ventilation, and stairs. You can’t legally use your new loft space without building control sign-off.
The main structural work covers:
- Reinforcing the floor to handle extra weight
- Fire-resistant walls and doors for safe escape routes
- Proper insulation for thermal efficiency
- Staircases built to specific width and height rules
A loft conversion specialist or structural engineer should check your property before you start. They’ll spot any issues and design solutions that meet the rules. Don’t skip this step—it protects your investment.
Planning Permission and Permitted Development
Most loft conversions in England fall under permitted development rights. That means you don’t need planning permission if you stick to the rules: no more than 40 cubic metres added for terraced houses or 50 for detached and semi-detached.
There are restrictions. You can’t extend past the original roof slope on any side facing a highway. Materials should match your home, and you can’t go higher than the current ridge.
You’ll need planning permission if you live in a conservation area, listed building, or a place with special rules. Mansard conversions almost always need permission because they change the roof so much. Always check with your local authority before you start anything major.
Costs, Value and Final Decision-Making
Loft conversion costs can swing pretty wildly depending on the type you go for. Each option adds different value and space, so it pays to know what you’re getting into.
Loft Conversion Cost Factors
Several things push your final loft conversion bill up or down. The type of conversion is the biggest factor.
Rooflight (Velux) conversions start at about £50,000, and they’re the cheapest since you don’t change the roof. Dormer conversions kick off around £55,000 and give you more space for a bit more money.
Hip-to-gable conversions start from £60,000 because of the extra structure involved. Mansard conversions are at the top end, starting from £69,000. Modular conversions start at £53,000 but can end up costing more, depending on what you want.
Your own costs depend on:
- Size of the conversion – bigger spaces need more materials and labour
- Structural work needed – strengthening floors or swapping out roof structures adds cost
- Finishes and fittings – bathrooms, built-in storage, and fancy fixtures all add up
- Access requirements – tricky site access makes labour more expensive
- Location – London and the South East are usually 20-30% pricier than elsewhere
Impact on Property Value
A loft conversion can bump up your property value by as much as 20%. The actual increase depends on the type of conversion and your local market.
Adding bedrooms gives you the best return. Turning your loft into a bedroom with an en-suite usually beats just making an office or storage space. In places where bedrooms are in high demand, you’ll see the biggest gains.
Mansard and hip-to-gable conversions add the most value since they create the most living space—almost like adding a whole new floor. Dormers also do well, especially if you add a balcony or en-suite.
The local market matters a lot. In areas where family homes are in demand, adding bedrooms through a loft conversion is a smart move. The quality of the finish makes a difference too—professional jobs with proper sign-off add more value than DIY efforts.
Choosing the Right Loft Conversion for Your Home
Your roof structure really decides which conversion will work. Rooflight conversions are perfect if you’ve got enough headroom and want to keep things simple.
Pick a dormer if you need more headroom and space but don’t want to mess with the roof too much. They’re versatile and usually allowed under permitted development. Hip-to-gable is great for semi-detached or detached homes with hipped roofs.
Mansard conversions are best when you want the maximum space and your house is in a terrace. They’re ideal for adding multiple bedrooms or a master suite.
Think about:
- Your budget and how much value you want to add
- The amount of space you really need
- Planning permission in your area
- How much disruption you can handle
- Whether you want bedrooms, bathrooms, or flexible space
What you’ll use the space for matters too. A home office doesn’t need as much space as a bedroom with an en-suite. Families needing extra bedrooms get the most out of mansard or hip-to-gable conversions.
Frequently Asked Questions
Every loft conversion type comes with its own structural requirements, costs, and planning rules. Knowing these differences helps you pick the right one for your home and budget.
What distinguishes a dormer loft conversion from other types?
A dormer loft conversion adds a box-shaped structure that sticks out vertically from your sloped roof. This gives you a flat roof section instead of following the original pitch.
With vertical walls and right angles, you get full head height throughout the space. You can use regular upright windows, not just slanted roof windows.
Dormers usually run along the rear of your property. They add up to 50 cubic metres of space and usually fall under permitted development.
How does a mansard loft conversion alter the structure of my home?
A mansard conversion changes your roof into an almost vertical back wall at around 72 degrees. There’s a flat or nearly flat top section too.
This type basically adds a whole new storey, not just extra space in the roof. The steep back wall means you get the most usable floor area.
Windows go into box-shaped dormers that stick out a bit from the main structure. This design brings in loads of natural light and gives you as much headroom as possible.
Can a hip to gable conversion be utilised to maximise space in a semi-detached house?
Hip to gable conversions are ideal for semi-detached houses with hipped roofs, where all sides slope down. You turn one sloping side into a vertical gable wall, making a triangular end.
This new wall adds a lot of floor space and head height. You can often add a dormer too, for even more usable area.
It doesn’t work for terraced homes, but it’s a practical way for semi-detached houses to expand upwards. The gable end gives a big boost in usable space compared to the original hipped roof.
What are the typical planning permission requirements for each type of loft conversion?
Rooflight conversions usually count as permitted development since you’re just adding windows, not changing the roof. Most of the time, you won’t need planning permission.
Dormer conversions often fall under permitted development too, as long as they’re at the back. Still, it’s always best to check with your local planning office before starting.
Hip to gable conversions might need planning permission depending on your specific case and location. Mansard conversions pretty much always require full planning permission because they change the structure so much.
How do the costs compare for dormer, mansard, and hip to gable loft conversions?
Dormer loft conversions usually start from £55,000. That puts them somewhere in the mid-range, price-wise.
The cost varies depending on the dormer’s size and whether you go for a flat or pitched roof. It’s not always easy to predict, honestly.
Hip to gable conversions kick off at about £60,000. You’re paying more here because of the extra structural work.
If you add a dormer extension to the mix, expect the price to climb even higher. Some folks find the extra space worth it, though.
Mansard conversions sit at the top end, starting from £69,000. That higher price comes from all the major structural changes needed—think almost vertical back walls and a brand new roof structure.
It’s a big investment, but some people swear by the space and style you get in the end.
What factors should be considered when choosing the type of loft conversion for a property?
Start with your existing roof type. That really limits what you can actually do—hipped roofs work well for hip to gable conversions, but most roof types can handle dormers.
Think about how much extra space you want and, of course, your budget constraints. Rooflight conversions are definitely more affordable, but you don’t get much extra headroom. Mansard conversions give you loads of space, though they’re pricier.
Your property type matters too. Planning permission can get tricky depending on the house, and not every conversion style fits every home. Terraced houses, for example, can go for mansard conversions, but hip to gable just isn’t an option there.
Finally, what do you want to use the new space for? If you just need a quiet spot for a home office, a simple rooflight conversion might do the trick. But if you’re dreaming of extra bedrooms, you’ll probably need something bigger—like a dormer or mansard.
