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Home & garden.

Updated: 29 Oct 2021

Loft conversions: step-by-step guide

Discover how to get started on your loft conversion. Find out whether your loft is suitable, how to choose the best type of conversion and how to find a builder
Which?Editorial team
Architectural drawing 436691

There are a lot of seemingly complicated steps to getting your loft converted, so knowing where to start can feel daunting. To help you run through the process from start to finish, we've put together this step-by-step guide.

Assuming your house is suitable for a conversion, you'll need to measure the space accurately, pick from four main types of loft conversion and then choose a builder or architect.

But fear not – it doesn't necessarily need to be a complicated journey. Keep scrolling as we explain the key stages of a loft conversion.

Can my loft be converted?

Before you do anything else, you need to work out whether your loft space is actually suitable for a conversion.

Most homes will come with an allowance for permitted development (PD), which means that you can go ahead with your conversion without planning permission. However, if you live in a conservation area, or if your roof space isn't tall enough, it may be more complicated.

You can ask a builder, architect or surveyor to visit your home and check this out for you, but there are also a couple of checks that you can carry out yourself prior to this.

Look for other conversions on your street

To get a sense of whether your loft can be converted, see whether any similar properties on your street have had loft conversions. If you do spot examples, it's more likely to be a possibility.

If you can, it's also worth going one step further and asking to take a look at the loft of anyone in your street that has had it done. That way, you can get a sense of the size of the space and start to think about how you'll fill it up.

Measure the head height

The minimum height you need for a loft conversion is 2.2 metres and you can easily measure this yourself.

Run a tape measure from the floor to the ceiling at the tallest part of the room. If it's 2.2 metres or more, your loft should be tall enough to convert. Victorian houses tend to be lower than those built from 1930 onwards, so may not have sufficient head height.

On the subject of older houses, consider other obstacles, such as water tanks and chimney stacks, when planning your conversion.

Check what type of roof you have

Depending on when it was built, your home will either have roof trusses or rafters. By looking through your loft hatch, you should be able to tell straight away what type of roof you have.

  • Rafters run along the edge of the roof and will leave most of the triangular space below hollow.
  • Trusses are supports that run through the cross-section of the loft. Converting a loft with trusses is possible, but extra structural support is needed to replace the trusses and it's likely to be more costly.

Consider the floor below

Many people neglect to factor in changes to the floor below the loft when planning a conversion. It's worth having a think about where the staircase is likely to go and how much room it might take up. Even a well-designed, space-saving staircase could take up a sizeable chunk of a room, so make sure you have space you're happy to lose.

Once you've assessed whether you're able to have a loft conversion, check our page on loft conversion costs, which includes average prices, plus tips from experts and people who have had a loft conversion.

How long does a loft conversion take?

Ultimately, the answer to this question depends on the trader you're using and the type of loft conversion they're dealing with.

Roof light conversions are usually the quickest, taking around four weeks to complete. A dormer conversion can take closer to five weeks, while a hip-to-gable conversion can take around seven weeks. You can expect a mansard conversion to take closer to eight weeks to complete.

The first week or two will be spent preparing your home and gathering the materials and tools required. Work usually starts on the outside of your property. After that, the focus turns to the inside of your house and the flooring, insulation and stud walls. The final stage will deal with plastering, electrics and plumbing.

Types of loft conversion: what's the difference?

There are four main types of loft conversion: roof light, dormer, hip-to-gable and mansard. The one you choose is likely to be determined by a number of factors, including the type and age of house you live in, and your budget.

Roof light conversion

  • Pros An affordable option for buyers on a budget, suitable if you live in a conservation area.
  • Cons Offers far less space compared to a dormer or mansard conversion.

Roof light conversions are by far the cheapest and least disruptive option, as you won't have to make any changes to the shape or pitch of the roof. Instead, it's simply a case of adding in skylight windows, laying down a proper floor and adding a staircase to make the room habitable.

However, you'll need to have enough roof space already without having an extension for this type of conversion.

Roof light conversions

Dormer conversion

  • Pros An option for most houses with a sloping roof.
  • Cons More structural changes needed compared with a standard conversion, so can take a while to build.

A dormer loft conversion is an extension that protrudes from the slope of the roof. Dormers, in particular flat-roof dormers, are the most popular type of conversion. They're suitable for pretty much any home with a sloping roof. 

Dormer conversions are less expensive than mansard or hip-to-gable conversions, but will still add a good deal of extra headroom and floor space.

Dormer conversions

Hip-to-gable conversion

  • Pros Generally less expensive than extending outwards, more natural-looking compared with a dormer conversion.
  • Cons More expensive than a dormer conversion, only suits houses with a free sloping side roof.

Hip-to-gable conversions work by extending the sloping 'hip' roof at the side of your property outwards to create a vertical 'gable' wall, creating more internal loft space. This type of conversion will only work on detached or semi-detached houses, as it requires a free sloping side roof. 

If you have a detached house with sloping roofs on either side, you can build on both of these to create an even more spacious double hip-to-gable extension.

Hip-to-gable conversions

Mansard conversion

  • Pros Creates lots of new useable space, suitable for many different types of property.
  • Cons Can be particularly expensive, don't look very natural due to change in roof slope.

Mansard extensions run along the whole length of your roof and will alter the angle of the roof slope, making it almost vertical. These tend to be the most expensive type of conversion, but will result in a significant amount of extra space. 

Mansard conversions are suitable for most property types, including terraced, semi-detached and detached houses.  

Mansard conversions

How do I choose a builder or architect?

When hiring any tradesperson, it's best to start with a recommendation. Speak to friends and family, and have a look online to see if there are any local forums offering recommendations.

If you've spotted any loft conversions along your street and you feel comfortable knocking on some doors, ask your neighbours who they used and how they found them. 

When speaking with a builder or architect, ask to see examples of previous work. Most reputable companies will be happy to provide you with photographs, and some may be able to organise visits so you can speak to customers about their experiences and see conversions that they've completed up close. 

It's a good idea to get at least three quotes for the work that you're planning, but be sure to factor in recommendations and your gut feel on the person or company, as well as price.

You can also use our Trusted Traders search tool below to search for professionals near you.

Alternatively, for more expert advice on finding the right trader, explore the Which? Trusted Traders website.

Planning permission for a loft conversion

Many loft conversions are covered by permitted development (PD) rights and won't need planning permission. 

However, if you live on designated land or have a certain style of property that's tricky to convert, you may not be covered by permitted development.

You can find out more about whether you'll need planning permission, and any other permissions you might need, by visiting our guide to building regulations and planning permission

Should I tell my home insurance company about a loft conversion?

Yes, you should tell your insurer about any changes that will alter your home’s structure, habitability, security or value. For example, a loft conversion may increase its value and this will likely affect your buildings and contents insurance premiums.

When staying elsewhere while your loft conversion is completed, then you should tell your insurer about this as well, and try to give several weeks’ notice.

If you’re having serious building work done, consider specialist renovations insurance. This covers against things going wrong with the building work, materials and property owners’ liability.

Discover how home insurers score for customer satisfaction with our guide to the best and worst home insurance.