What You Need to Know About Dormer Loft Conversions
Mansard, dormer, hip to gable... There are so many loft options out there. The first in a new series looks at the dormer conversion
Graham Chappell
14 January 2016
With space at a premium across the UK, homeowners are increasingly turning to extensions and loft conversions to create a more comfortable home. There are many ways you can extend up into your loft, including dormer conversions, mansard conversions, roof light conversions and more. As part of our Loft Planning guide, this series will look some of the different types in detail, starting with dormer and L-shaped dormer loft conversions.
Beginning your loft conversion project? Read How Do I Begin a Loft Conversion?
Beginning your loft conversion project? Read How Do I Begin a Loft Conversion?
What is a dormer loft conversion – and is it right for your home?
What makes a loft conversion a dormer conversion is the angle of the box: the dormer extension walls sit at a 90 degree angle to the floor. An L-shaped dormer also extends out over the slim rear addition common on Victorian houses, as well as sitting on the main body of the home, as seen in this image.
Technically, any property with a pitched roof could have a dormer loft conversion. If you have a flat roof, there’s no need to go for a dormer, because there’s no pitch you’re building out from; a double mansard would be more typical in this case (more of which later in the series).
Get expert advice on when you might need Planning Permission
What makes a loft conversion a dormer conversion is the angle of the box: the dormer extension walls sit at a 90 degree angle to the floor. An L-shaped dormer also extends out over the slim rear addition common on Victorian houses, as well as sitting on the main body of the home, as seen in this image.
Technically, any property with a pitched roof could have a dormer loft conversion. If you have a flat roof, there’s no need to go for a dormer, because there’s no pitch you’re building out from; a double mansard would be more typical in this case (more of which later in the series).
Get expert advice on when you might need Planning Permission
Pros and Cons
You don’t necessarily need Planning Permission…
A big reason people go for a dormer loft conversion is that you can build under Permitted Development (PD). PD allows you to extend up to 40 cubic metres for a terraced property, and 50 cubic metres for a semi-detached or detached house. Permitted Development doesn’t apply if you live in a flat or a conservation area (you can find out whether you’re in a conservation area on your local council website). Under PD, the dormer must be set in 200mm from the eaves.
If you want to go for anything bigger, you’ll need to apply for Planning Permission.
You don’t necessarily need Planning Permission…
A big reason people go for a dormer loft conversion is that you can build under Permitted Development (PD). PD allows you to extend up to 40 cubic metres for a terraced property, and 50 cubic metres for a semi-detached or detached house. Permitted Development doesn’t apply if you live in a flat or a conservation area (you can find out whether you’re in a conservation area on your local council website). Under PD, the dormer must be set in 200mm from the eaves.
If you want to go for anything bigger, you’ll need to apply for Planning Permission.
…but it’s worth getting a Certificate of Lawful Development
Even if you qualify for Permitted Development – let’s say you want to build a dormer of 35 cubic metres on a terraced house in a non-conservation area – it’s always worth running your plans by your local council first, to make sure they’re on the same page. You just need to write to them and explain your plans and why you believe the conversion can be done under PD. If they agree, they will issue you with what’s called a Certificate of Lawful Development (COLD) for your dormer loft conversion.
It is possible to apply retrospectively, but if the council have interpreted the regulations differently, in the worst case scenario you might be asked to alter your conversion to something they believe to be within PD rights. So it’s worth applying for a COLD early to avoid any surprises.
Even if you qualify for Permitted Development – let’s say you want to build a dormer of 35 cubic metres on a terraced house in a non-conservation area – it’s always worth running your plans by your local council first, to make sure they’re on the same page. You just need to write to them and explain your plans and why you believe the conversion can be done under PD. If they agree, they will issue you with what’s called a Certificate of Lawful Development (COLD) for your dormer loft conversion.
It is possible to apply retrospectively, but if the council have interpreted the regulations differently, in the worst case scenario you might be asked to alter your conversion to something they believe to be within PD rights. So it’s worth applying for a COLD early to avoid any surprises.
You get more space than in other types of loft conversion…
Most people tend to go for a dormer loft conversion because it achieves the maximum amount of internal space, as all of the internal walls are vertical.
Most people tend to go for a dormer loft conversion because it achieves the maximum amount of internal space, as all of the internal walls are vertical.
…but it’s visually boxy
The downside to the dormer is it’s very angular, and it can look a bit like you’ve just stuck a box on the side of your property. If your local planning authority is strict (it does vary from borough to borough) or you have to apply for Planning Permission, the planning team may insist you do a mansard conversion rather than a dormer. A mansard sits at 70 degrees, so is more sloped, and therefore visually softer than the perpendicular dormer.
The downside to the dormer is it’s very angular, and it can look a bit like you’ve just stuck a box on the side of your property. If your local planning authority is strict (it does vary from borough to borough) or you have to apply for Planning Permission, the planning team may insist you do a mansard conversion rather than a dormer. A mansard sits at 70 degrees, so is more sloped, and therefore visually softer than the perpendicular dormer.
Dormer windows can be different sizes…
There are several things you can do with a dormer window, and most will depend on the style of your own property and the homes nearby. Generally, the dormer window will need to bear some relation to the home’s existing windows, and be smaller than them.
In more cottage-style properties, two or three smaller dormer windows might be installed for a much softer look, as on this house. Although this means there’s less room inside, it generally looks much better externally.
Discover what to consider when planning a loft conversion
There are several things you can do with a dormer window, and most will depend on the style of your own property and the homes nearby. Generally, the dormer window will need to bear some relation to the home’s existing windows, and be smaller than them.
In more cottage-style properties, two or three smaller dormer windows might be installed for a much softer look, as on this house. Although this means there’s less room inside, it generally looks much better externally.
Discover what to consider when planning a loft conversion
…and different styles
Technically, any material could be used for a dormer window, from aluminium or UPVC to the traditional wooden sash windows seen in so many Victorian properties.
The Certificate of Lawful Development will stipulate your window options. Depending on your local council and the strictness of the regulations, the COLD may dictate the exact type of windows you can have. For example, the planners may accept the application under PD with the requirement that all windows be timber sash, or they might be more flexible and give you options.
Technically, any material could be used for a dormer window, from aluminium or UPVC to the traditional wooden sash windows seen in so many Victorian properties.
The Certificate of Lawful Development will stipulate your window options. Depending on your local council and the strictness of the regulations, the COLD may dictate the exact type of windows you can have. For example, the planners may accept the application under PD with the requirement that all windows be timber sash, or they might be more flexible and give you options.
You can probably have a Juliet balcony
Most conversions can have a Juliet balcony, with the exception of properties in conservation areas. The size of the doors will usually be dictated by the property and the size of the opening, as well as cost and, of course, preference.
Most Juliet balconies are 2100mm high and 1200mm wide, but you could go for triple- or even quadruple-size windows if you’re granted Planning Permission. This would be more typical of 1930s and onwards houses that don’t have rear additions that constrain the possible size.
If you do go for a Juliet balcony, you’ll need to have a balustrade that’s at least 1100mm high. You could do this in railings, glass – or whatever material you fancy really. In general, there are no planning restrictions on the type of material you can have if you’re allowed a Juliet balcony, but it is worth detailing it in your plans to ensure you’re on the same page as your local council.
Most conversions can have a Juliet balcony, with the exception of properties in conservation areas. The size of the doors will usually be dictated by the property and the size of the opening, as well as cost and, of course, preference.
Most Juliet balconies are 2100mm high and 1200mm wide, but you could go for triple- or even quadruple-size windows if you’re granted Planning Permission. This would be more typical of 1930s and onwards houses that don’t have rear additions that constrain the possible size.
If you do go for a Juliet balcony, you’ll need to have a balustrade that’s at least 1100mm high. You could do this in railings, glass – or whatever material you fancy really. In general, there are no planning restrictions on the type of material you can have if you’re allowed a Juliet balcony, but it is worth detailing it in your plans to ensure you’re on the same page as your local council.
You can install a skylight
The only thing to consider with a skylight is that it doesn’t go above the roofline if you are building under Permitted Development, as this will require Planning Permission. You can find some windows that are almost flush, so you shouldn’t have an issue, but it’s worth running it by your planning authority first to check.
The cost will vary, depending on the size you choose, what the planning authority will allow, structural considerations, and the manufacturer. Skylights can range from £600 for a small one up to £50,000 for a full-width, full-length cascade of glass across the room, landing and stairs.
The only thing to consider with a skylight is that it doesn’t go above the roofline if you are building under Permitted Development, as this will require Planning Permission. You can find some windows that are almost flush, so you shouldn’t have an issue, but it’s worth running it by your planning authority first to check.
The cost will vary, depending on the size you choose, what the planning authority will allow, structural considerations, and the manufacturer. Skylights can range from £600 for a small one up to £50,000 for a full-width, full-length cascade of glass across the room, landing and stairs.
Dormers can lend themselves to window seats
Because of the perpendicular angles, dormer windows – particularly the smaller, individual ones – lend themselves well to window seats, without the worry of having walls sloping in on you.
They provide a great little nook for storage, too – consider building in a drawer or a compartment with a lift-up lid underneath the seat.
Check out storage ideas for small-space living
Because of the perpendicular angles, dormer windows – particularly the smaller, individual ones – lend themselves well to window seats, without the worry of having walls sloping in on you.
They provide a great little nook for storage, too – consider building in a drawer or a compartment with a lift-up lid underneath the seat.
Check out storage ideas for small-space living
They’re good for storage and window dressings
What makes dormers good for storage are the vertical walls: they make it much easier for the owner to build in or have freestanding wardrobes in the corners of the room.
The vertical walls also make the windows easier to dress. The pitched roof at the other side (usually at the front of the home) will typically feature a Velux window that works with a blind.
TELL US…
Have you recently converted your loft? Did you decide to go for a dormer? We’d love to read your story in the Comments below.
What makes dormers good for storage are the vertical walls: they make it much easier for the owner to build in or have freestanding wardrobes in the corners of the room.
The vertical walls also make the windows easier to dress. The pitched roof at the other side (usually at the front of the home) will typically feature a Velux window that works with a blind.
TELL US…
Have you recently converted your loft? Did you decide to go for a dormer? We’d love to read your story in the Comments below.
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If your roof joists are suitable for use then the alterations to the roof including tiling should be around 10k. Get a builder to quote and check your costs with a surveyor. Just check if you need planning permission ( in most parts of the country you do if you are altering the roof line).