In a recent report, Nationwide revealed that adding usable space is the key to adding value to your property.
Read on to see the best way to boost the value of your home, plus our expert tips on managing a conversion.
How much value does a loft conversion add?
According to research conducted by Nationwide in October 2025, a loft conversion or extension that incorporates a large double bedroom and a bathroom can increase the value of a three-bedroom, one-bathroom house by as much as 24%.
The report goes on to say that increasing the floor area of your home by 10% could add up to 5% value, while adding an extra bathroom could add up to 4%.
Commenting on the figures, Andrew Harvey, Nationwide’s Senior Economist, said: ‘We’ve used our house price data to look at the factors that affect the values of homes as well as the potential to add value.
‘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.’
To see if this project fits your budget, our guide to how much a loft conversion costs features the latest data from the Building Cost Information Service
Why an extra bedroom is key
The report also reveals that adding space for a double bedroom can add 13% to the value of a typical two-bedroom house.
The impact varies by property type and size. For example, adding a third bedroom to a two-bed home can add 13-17%, depending on the size of the property, while adding a fourth bedroom to a three-bed home adds between 10 and 13%.
Data source: Nationwide House Price Index special report, 2025. The research assumes the additional bedroom has a floor area of 13m², which is a standard double. Smaller bedrooms will add less value.
Hannah Healey, Which? home improvements expert
‘This analysis from Nationwide offers more proof that adding space is the key to adding value to your home.
‘To maximise the value added, ensure the space is practical and well-designed. You won’t see the same increases in value for a poor quality conversion, or a conversion added to a house that already had plenty of bedrooms.
‘You should also bear in mind the number of bathrooms you have – ideally, you want a bathroom on every floor where there’s a bedroom.
‘If your home is in a high-demand location (eg, with good schools and transport links) or an area in which space is at a premium you will likely see a greater increase in value following a loft conversion.’
For more on this topic, read ‘Does a kitchen renovation add value to your home?‘
Navigating the loft conversion process
While it’s a compelling way to add value, a loft conversion is a complex and disruptive project.
Careful planning will help you maximise the space and value uplift.
Before you begin, consider the following:
- Ensure your loft can be converted It will require a ceiling height of greater than 2.2 metres.
- Budget carefully We always recommend you add at least 10% to your budget to cover contingency costs.
- Pick your professionals You’ll always need to consult an engineer to ensure your conversion is safe, but working with an architect or experienced builder will likely help you to maximise your return on investment.
- Check building regulations These will determine the type of extension you’re allowed to do.
For further advice, consult our step-by-step guide on how to plan a loft conversion
Planning permission and building regulations for lofts
One of the most common reasons homeowners regret renovations is that costs spiral or the end result doesn’t meet expectations.
Ensuring your conversion complies with local laws is essential for a smooth sale later on.
In March 2025, we surveyed 33 Which? members who had converted their loft in the last 10 years.
One member regretted not being more conscious of the regulations during the conversion: ‘I was not aware of all the height lost in the loft due to the suspended flooring and the extent of the insulation required at roof levels as compared to the loft pre installation.’
Another said they regretted not going for a full conversion: ‘I would like to have had a hip roof at the front as well as the back.’
Read our guide to loft conversion building regulations and planning permission for information on permitted development, party wall agreements and more
How to find a reputable builder or loft conversion specialist
Finding a reputable specialist is key to ensuring a successful project. The figures above assume that the conversion is well executed – a poorly finished conversion may have a detrimental impact on the value of your home.
A vetted professional will also ensure your project meets building regulations, protecting your investment and preventing legal headaches when you eventually try to sell the property.
Use the Which? Trusted Traders tool to find a reliable professional in your area:
For further guidance, follow our advice on finding professionals to work on your loft conversion.