The Ultimate Loft Conversion Guide for the UK

Loft conversions are increasingly popular for Britons who want more space, but don’t want to lose tens of thousands of pounds to stamp duty, removals, solicitor fees, and the other services you need to hire to move house. Fortunately, a loft conversion won’t just cost money — it makes money too.

This short guide gives you all the information you need to make an informed choice about your loft conversion and whether you want to start building one.

How Much Does a Loft Conversion Cost?

There isn’t a simple answer to this, unfortunately. It depends on a number of things, including the type of loft conversion, whether or not you need planning permission for it, the rooms that you’re building, the quality of the finish, whether you’re also asking your builders to do the interior decorating, and whether you would like to add plumbing to the new rooms.

The cost of your loft conversion can be anything from £13,000 to £40,000+. The important thing is to fully understand what your quotes include and to choose a company based on their past work as well as cost, because the cheapest option could end up costing you more in the long run.

In short: Anything from £13,000-£40,000+, so it depends

How Much Does a Loft Conversion Add to the Value of My House?

Nationwide carries out annual surveys on this subject, and loft conversions consistently add the most onto house values. This adds up to around 20% or £37,000, depending on your loft conversion and where you are.

This is more than extensions, extra bathrooms, and extra bedrooms put together.

In short: Up to £37,000

How Long Does a Loft Conversion Take to Build?

There are 4 main types of loft conversions; velux, dormer, hip to gable, and mansard. Velux and dormer loft conversions take the least time to build because the exterior changes are really minimal. Mansard loft conversions take the longest because they have to change the entire roof and then the interior, rather than just reinforcing the structure and adding windows.

Again, this all depends on things like the materials used, the state of your house, the size of the loft conversion, and the type. But, to give average figures, a velux or dormer loft conversion takes around 6–8 weeks, while mansard loft conversions can be 12 weeks or more.

In short: 6–12 weeks

Do I Need Planning Permission to Build a Loft Conversion?

This largely depends on your house, your area, and the type of loft conversion you’d like to build.

Velux and dormer loft conversions can usually be built as permitted developments if you work within the criteria and your house hasn’t already used up all of its permitted developments.

Hip to gable and mansard loft conversions will always need planning permission because they make large changes to the exterior of the building.

If you live in a listed building or a conservation area, there will be further restrictions placed on what you can do to your home and you may even be restricted in the type of loft conversion you can build (even with planning permission). Your area and the local authority has the largest impact on whether or not you need permission; if you’re building a loft conversion in Hertfordshire it’s going to have very different requirements to a loft conversion in London.

In short: Some loft conversions can be built as permitted developments, but others need planning permission

What are the Different Types of Loft Conversions?

Velux loft conversions don’t make any major changes to the exterior of the house — they just add windows and reinforce the structure. They’re the cheapest and fastest to build, but you’re limited in how much additional space you’ll gain. They’re good for houses with a lot of existing roof space.

Dormer loft conversions add small boxes to the exterior of the roof called dormers. These add more headroom to the loft space, but not by much. They’re quite cheap and fast to build, but you’re not expanding the roof space by much. They’re good for traditional buildings where a dormer won’t look out of place.

Hip to gable loft conversions change the end of the roof from angling inwards (a hip) to going straight up (a gable). You will need planning permission for this, which means that even without the extra build time it takes a lot longer to get started and will cost more to build. They’re good for detached houses, but can look odd on semi-detached houses if your neighour hasn’t done it.

Mansard loft conversions open up the roof giving it 4 sides rather than 3. This means that the rooms in a mansard conversion are a lot bigger, more square, and easier to furnish. However, that does come at a larger cost and longer build time.

Is it Better to Move House or Build a Loft Conversion?

This depends entirely on your circumstances. If you’re very happy where you are and don’t mind stairs, a loft conversion is the clear winner. Especially since the average cost of moving home is now £12,000 in the UK.

If you’re looking forward to more than just extra space in the house, moving is the better choice. Especially if the additional stairs might be a problem for you or the other members of your family.

In short: The maths can make loft conversions the more cost effective option, but you need to weigh up your reasons for moving

Where Can I Get More Information About Loft Conversions?

Still want more? There is a lot of useful information about loft conversions here: