Loft conversions remain one of the best investments homeowners can make in 2026. Adding a bedroom and bathroom in your loft can increase your property value by 15 to 20 percent.
Average Loft Conversion Costs in 2026
- Velux/Rooflight conversion: £25,000 to £40,000
- Dormer conversion: £35,000 to £60,000
- Hip-to-gable conversion: £45,000 to £70,000
- Mansard conversion: £55,000 to £80,000+
London prices are typically 20 to 30 percent higher than the national average.
What Affects the Cost?
- Property size and roof structure
- Bathroom installation: Adding an en-suite adds £5,000 to £10,000
- Staircase complexity
- Structural requirements: Steel beams and additional work add cost
- Finish quality: Basic versus high-end fixtures
- Planning requirements: Full planning applications cost more in fees
Professional Fees to Budget For
- Architectural drawings: £1,500 to £3,000
- Structural calculations: £500 to £1,200
- Planning application fee: £258 (2026 rate)
- Building control fee: £400 to £900
- Party Wall surveyor: £700 to £1,500 per neighbour
How to Save Money
- Choose a Velux conversion if headroom is adequate
- Get at least three builder quotes
- Use a combined architectural service for all drawings
- Plan during quieter months for better builder rates
- Avoid design changes once construction starts
Is It Worth It?
A well-designed loft conversion can add £40,000 to £80,000 to your property value. The return on investment typically ranges from 50 to 75 percent.
Get Started with QM Designs
We provide complete loft conversion drawing packages at competitive prices. Get a free quote for your loft conversion project.
