How much does a loft conversion cost in 2025?

A loft conversion can be a great way to add value and living space to your home, but it doesn't come cheap.

To find out how much a loft conversion costs in 2025, the Building Cost Information Service (BCIS) provided us with typical costs for different sizes of rooflight and dormer conversions.

We also share expert tips on how to save money.

Wondering where to start? Read our guide on how to plan a loft conversion

Loft conversion costs 

The cost of a loft conversion can vary dramatically based on size and quality.

Our prices for rooflight and dormer conversions include labour and materials. 

They cover the clearing of materials from the loft space, relocating an existing water tank, insulation of walls and ceiling, softwood framing (where wood is placed to make new structures), plasterboard on walls and ceiling, a new straight flight of stairs, new electrics and heating.

The costs don't cover internal partition walls and painting, and the final decoration.

Rooflight loft conversion costs

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Dormer loft conversion costs

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Loft conversion cost breakdown

Several factors will impact the amount you need to spend on each element of your loft conversion, for example, the location of your property and whether you need to use an architect. But regardless of your total spend, your budget should roughly break down as follows: 

• Labour costs: 35-40%
• Materials: 25-30%
• Fixtures and fittings: 10-15%
• Planning and permissions: up to 5%
• Contingency budget: no less than 10% (to cover any issues that arise during the project). 

Using the BCIS data above and these percentages, we've calculated an approximate breakdown of the loft conversion cost.

Rooflight loft conversion cost breakdown

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Note that our cost breakdowns are approximate, and will vary significantly depending on whether you add a home office, a bedroom or a bedroom with en suite.

Dormer loft conversion cost breakdown

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A large dormer conversion will cost almost twice as much as a small conversion. 

Labour and materials will likely make up the bulk of your spend. 

Considering an extension? Find out how much an extension costs in 2026

Does a loft conversion add value to your property?

According to a 2025 report produced by Nationwide,* a loft conversion can add up to 24% to the value of your property.

Andrew Harvey, Nationwide's senior economist, says: 'Location remains key to house values, but other factors, such as the number of bedrooms, are also important to homebuyers.

'Home improvements that increase the size of the property, such as an extension or loft conversion, remain a compelling way to add value.' 

Nationwide's report estimates that a 10% increase in floor space can add 5% to the price of a typical house, but additional bedrooms are the key to adding value.

Andrew adds: 'Homeowners who add a loft conversion or extension, incorporating a large double bedroom** and bathroom, can add as much as 24% to the value of a three-bedroom, one-bathroom house.' 

Loft conversions will generally add more value to your home in London and the South East, where space is at a premium, than in the North and South West. 

What other factors affect loft conversion costs?

The cost of a loft extension can vary significantly depending on the type of conversion, your home's location and whether you need planning permission. Read on to find out more about these and additional factors.

Type of conversion

Conversions that require structural work (such as a dormer or a mansard) will cost more than a rooflight conversion. 

How you plan to use the space can also impact costs. For example, if you're having a bathroom fitted, the pipework and waterproofing will add to the cost. That said, larger-scale conversions tend to have a greater return on investment when it comes to selling your house.

Type of roof

Houses built before 1970 tend to have old-style rafters, which are open and self-supporting, making them easier to convert. 

Houses built after about 1970 often have roof trusses – a framework that spans the cross-section of the roof. These are trickier to convert, as more work is needed to ensure they remain structurally sound, which can double the cost.

House location 

The area you live in is likely to affect the cost of a conversion. Typically, if you live in Northern Ireland, you'll pay less, while those in South East England will pay more. 

If you live in London, the higher cost of labour and materials means you're likely to face higher costs than anywhere else in the UK. However, you should also see a greater return on your investment, as space is at a premium in the capital. 

Whether or not you need a party wall surveyor

If any of the work affects the adjoining wall between your house and your neighbour's, you'll need to serve your neighbour with a Party Wall Notice. This outlines the work you're proposing and should include detailed plans.

Your neighbour can appoint a surveyor to look at the plans if they have any concerns. If this is the case, it's up to you to cover the costs, but you can improve your chances of keeping costs fair by including some suggested surveyors with your Party Wall Notice. Ask your builder or architect for recommendations of reputable companies.

Whether or not you need planning permission

Most loft conversions can be carried out without planning permission under permitted development. But if you do need it, an application can cost up to £1,000. Find out early whether you'll need planning permission, so you can factor it into your overall budget.

Read our guide to loft conversion planning permission and building regulations to find out more

How to save money on a loft conversion

These tips should help you shave money off the cost of your loft conversion: 

• Get more than one quote: Get at least three quotes for any building work to ensure the prices are competitive. 
• Ask for a fixed-price contract: The price of a fixed contract cannot go up or down except in the case of certain predefined circumstances, so you won't have any nasty surprises later on.
• Add a contingency budget: It's harder to blow the budget if you've prepared for all eventualities, so add no less than 10% to your total budget to cover any unexpected additional costs. If you're having structural work done, aim for 15-20%. 
• Find your own fixtures and fittings: There are plenty of deals to be had by looking online, or looking for second-hand items on Facebook Marketplace or eBay (read how to buy second-hand online for top tips and safety advice).

Is it possible to DIY a loft conversion?

For most homeowners, it's not possible to DIY a loft conversion – especially if it requires structural work to convert it into a living space (rather than a simple conversion to use it as storage space, for example).

Not only will you need extensive knowledge of structural works (including load-bearing requirements), your conversion will need to comply with building regulations, regardless of whether or not you need planning permission. These are in place to ensure any work done is structurally sound, the new room is fire-safe, and that sound is reasonably insulated between the loft and the rooms below.

Non-compliant work can be unsafe, lead to issues selling your home in future, and the local authority can force you to remedy the work, often at great cost.

You can save costs on labour by decorating the loft yourself, but it's best to leave the rest to a professional. 

How we calculate our loft conversion costs

The BCIS database analyses price data from various sources. 

Materials costs are based on the best trade prices from a range of suppliers across the UK, which are then benchmarked to reveal the best national average.  

Labour rates are based on the current Building and Allied Trades Joint Industrial Council wage agreement. 

To arrive at the cost breakdowns, we applied the percentages of your budget you can expect to spend on labour, materials, fixtures and fittings, planning and permissions, and a contingency budget to the BCIS figures.

Insulation is also an important part of your conversion, so find out more in our guide to types of loft insulation

*Nationwide data from research conducted in 2025. The methodology correlates the price paid for a property with a set of property characteristics (including property type, age, number of bathrooms, number of bedrooms, and floor area), region, and locality (ACORN). The data was drawn from Nationwide’s sample for the period October 2024 to September 2025.

**The additional bedroom is assumed to have a floor area of 13 square metres.