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The complete loft conversion guide for UK homeowners

What does it take to convert your loft? Over the course of this guide, we’ve collected all our expert knowledge on the subject, covering everything from suitability, design, planning, all the way to construction.

8 min read

There are plenty of good reasons why loft conversions are one of Britain’s most loved home extension projects.

By getting previously dead space working that bit harder, you can unlock a whole new storey of living space. This can be turned into a bedroom, playroom, or home office - all of which are adaptable and desirable spaces. Unlike ground-floor extensions, which expand existing rooms, these new rooms statistically provide more home value, making loft conversions a great long-term investment.

So, how do you go about creating these super projects? At Resi, our extension platform has helped over 4000 customers grow their homes. With everything you need to get building, all under one roof, we know all about the ins and outs of loft renovations.

Here’s our breakdown of what your extension journey may look like.

What is a loft conversion and how you could make the most of it?

Loft conversions take the existing space you have at the top of your house, which is typically underdeveloped, either empty or housing a boiler, and transform it into a new habitable space.

If your loft is large enough, this conversion can be as simple as doing up your flooring, walls, and getting a set of new windows installed. However, you can also choose to extend the space by raising the headroom and reducing the pitch of your ceiling.

When taking on a loft conversion, it’s important to set clear goals for your project and maximise your efforts at every stage. Want to add the most value to your home? Opt for a new bedroom with an ensuite. Want a pleasant place to work while at home? Invest in glazing and add in plenty of storage, so the room doesn’t become cluttered.

What are the various types of loft conversion?

Loft conversions come in all shapes and sizes, with something to suit every goal and budget. When sitting down with a designer, you’ll likely hear these variations cropping up in the conversation.

Skylight / Room in loft conversion

Sometimes simple is best and it doesn’t get more simple than this. A skylight (also known as a ‘room in loft’ or ‘Velux’ conversion) involves keeping the structure of the room as it is and simply fitting it out with better flooring, insulation, walls, and windows. This is the most budget-friendly conversion but does require you to have at least 2.1 metres of headroom available.

Dormer loft conversion: side, rear and pitched

This is a very popular and cost-effective option. They create a structural extension that projects from an existing roof, often resembling a stylish box attached to the top of your house. Homeowners like this option because it adds a lot of headroom, allows traditional windows to be installed, and tends to be less expensive than other loft extensions.

loft conversion dormer underside

Hip-to-gable loft conversion

Favoured by homeowners in end of terraces, semi-detached, and detached homes, this conversion will transform an existing hipped roof into a gable one. This involves straightening an inwardly slanted end roof, turning it into a vertical wall. For the maximum amount of space, you can choose to combine this project with a dormer - though this will likely require a six-figure budget.


If you’re looking to retain a more traditional aesthetic for your property, then a mansard might be the answer. It is typically created by raising the party wall (the wall shared with a neighbour) in order to create a flat roof and an outer wall that slopes inwards at around 72 degrees. Councils tend to favour mansard additions, as they can help retain a building’s character.

What are your options according to your house?

Because of the range of options available, a loft conversion is a flexible option for anyone with a loft to hand. However, if you want to use permitted development right, or simply go with what is a natural fit, there are some projects more suited to specific kinds of houses.

Terraced house

While terraced properties still benefit from permitted development rights, you’ll need to make sure the extension you select both complies with design regulations, while also staying on the good side of your neighbours.

Under permitted development any loft conversion for a terraced house cannot exceed 40 cubic metres, nor can any extension exceed the existing height of your roof or those of your neighbours.

You’ll also need to bear in mind that having two sets of neighbours will bring up double the party wall matters. If both parties dissent, you could have two simultaneous legal matters underway, which can be pretty costly. To avoid this, you might keep things simple with either a room in loft or even small dormer addition.

loft conversion street view

Semi-detached house

For those of you who own traditional semi-detached houses, you’ll find your options more expansive than your terraced counterparts.

Under permitted development rights, you’ll now be able to add up to 50 cubic metres of new space, opening up larger loft conversion possibilities.

Because you have a party wall in place, a mansard could be a good option for this type of property, especially if you live in a conservation area and are looking for an uncontentious design for your council to consider.

Detached house

Owners of detached properties have the most options available to them, and any loft conversion would be a great addition to the property. If you’re looking to maximise on space and you suffer from a low hipped roof, then a hip to gable would allow you to open the roof up and even provide the opportunity for a new dormer.

Though there are fewer restrictions and you likely won’t have to deal with party wall matters, if you want to use your permitted development rights, you’ll still need to ensure your design meets the guidelines. You should also know the scheme does apply to listed building and rights can be limited for properties in conservation areas.

Ideas and examples of loft conversions

loft conversion living room

loft conversion balcony entrance

A skylight loft conversion with balcony

Renovating without a dormer might seem tricky, but you’ll be surprised by what a good designer can unlock.

With this Southwark loft conversion, we married together with a classic skylight conversion with a new balcony, giving these London dwellers plenty more space to enjoy. Our designers made sure to include plenty of glazing so the space felt bright and spacious, even with the pitched roofs.

Because we added a balcony, this project required a full planning application, which our team managed on the family’s behalf.

loft conversion kitchen

loft conversion living room pitched

A dormer loft extension in Lambeth

We used a dormer to bring more living space to this top floor London flat.

This house already had a side dormer in place and, with the building sat in a conservation area, our team had to make sure the latest addition wasn’t going to get too much push back from the council. Therefore, we enlarged this existing loft extension to create a large living space and find room for a small study upstairs.

What are the building regulations for loft conversions?

All loft conversions (and homes in general) must meet building regulations. This means having your project assessed either by an approved inspector or your local building control, who will look at not only the room but the stairway too.

At a minimum, you’ll need to bring on a structural engineer to provide key calculations. However, we always recommend taking this a step further by commissioning a building regulations package. This will provide all the details your contractor will need to fulfil the requirements.

Your building regulations package will include…

  • Structure
  • Fire Safety
  • Site preparation and resistance to contaminants and moisture
  • Toxic substances
  • Sound
  • Ventilation
  • Hygiene
  • Drainage and waste disposal
  • Combustion appliances and fuel storage systems
  • Protection from falling, collision and impact
  • Conservation of power and fuel
  • Access to and use of buildings
  • Electrical safety in dwellings

Insulation regulations

Insulation will be a major consideration for your extension, as most heat from a property escapes through the roof. This is another major benefit of converting your loft, as it allows you to trap this heat. However, in order to get the best results, you will need to invest in good quality insulation.

Under building regulations, your insulation should provide a U-value of at least 0.16W/m2K, but you’ll want to aim for something higher than this minimum level.

How much does a loft conversion cost?

Pricing a loft conversion can be quite tricky. For instance, your could achieve a skylight conversion for as little as £25,000, whereas a hip to gable (with dormer) could cost up to £200,000 - that’s a big difference!
However, on average, we do recommend you give yourself a healthy budget of between £55,000 - £80,000.

How much your loft conversion will cost will depend on the type of project you want to pursue, where you are in the UK and the quality of your services and materials.

Learn more about the cost breakdown for a loft conversion.

Get a quick quote for design services here or try our construction calculator.

Do I need planning permission to convert my loft?

Short answer - maybe not.

Loft conversions can come under permitted development rights, which means you don’t need a full planning application, as long as the design guidelines have been met. These guidelines are…

  • A volume allowance of 50 cubic metres additional roof space for detached and semi-detached houses
  • Uses similar building materials to the existing house
  • The development must not include a window in any wall or roof slope forming a side elevation of the dwelling house
  • The roof pitch of the principal part of the dwelling must be the same as the roof pitch of the existing house
  • A dormer wall that is set back at least 20cm from the existing wall face
  • Has windows that are non-opening if less than 1.7m from the floor level
  • Has side windows that are obscured/frosted

Keep in mind, even with permitted development rights, you’ll need to apply for a lawful development certificate. This process takes at least 8-10 weeks.

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