We surveyed over 100 residential architects on Design for Me, from across the UK asking, ‘How much does a typical loft conversion cost?’.
This updated survey provides a current data-backed view of what you can expect to pay for a typical loft conversion, broken down by region, as well as related costs like architect’s fees and other professional services.
Image above by Ayca, architectural designer on Design for Me. See her full profile here.
‘Typical’ loft conversion cost in 2025
These are the average prices given from the 100+ architects surveyed for the starting price for a typical project.
| Location | Average Loft Conversion Cost | Average Mansard Roof Extension Cost |
|---|---|---|
| UK (Overall) | £74,143 | £107,425 |
| Outside London | £55,821 | £97,385 |
| London / South East | £88,000 | £109,804 |
These figures assume a simple habitable space, including stairs, roof lights (or dormer windows), finishes, lighting, heating, and decorations. Bathrooms and bespoke joinery are not included, which would increase costs.
Architect’s Fees for Loft Conversions
Our survey found that architects typically charge:
- Average UK (all regions): ~11% of the total project cost
- Outside London: ~9%
- London / South East: ~13%
For a £74,000 loft conversion, full architectural services could cost roughly £8,000 – £11,000. See our full article covering architect costs here: How Much does an Architect Cost?
Other Professional Fees
The following is the average estimate provided by the 100+ architects surveyed. This is the expected combined costs for structural engineers, planning consultants, and other services (excluding party wall awards).
- Average UK: £5,000
- Outside London: £3,466
- London / South East: £6,421
Tips to Manage and Reduce Costs
- Hire an Architect Early – They’ll help you maximize space, navigate planning regulations, and avoid costly mistakes.
- Get Multiple Quotes – Aim for 3–5 competitive bids from vetted contractors.
- Value Engineering – A skilled architect can help you identify where to save money without sacrificing quality.
- Shop Around for Fixtures and Finishes – Trade discounts can add up.
