A loft conversion is one of the smartest ways to add space and value to a London home. But the first question every homeowner asks is the same: how much will it cost? This guide gives realistic 2026 prices for Hayes and West London, and explains what affects your final quote.
Average Loft Conversion Costs in London (2026)
As a guide, most of our customers budget in these ranges:
- Velux (rooflight) conversion: £25,000 – £40,000
- Dormer conversion: £35,000 – £55,000
- Hip-to-gable conversion: £45,000 – £65,000
- Mansard conversion: £55,000 – £80,000+
These are typical guide prices for London homes. Your exact price depends on your roof, your design and your finishes, which is why we always carry out a free site survey before giving a fixed quote.
What Affects the Cost of a Loft Conversion?
- Type of conversion – a simple Velux conversion costs less than a mansard because it changes the roof structure less.
- Size of the loft – larger floors and taller roofs need more structural steel and materials.
- Bathroom or en-suite – adding plumbing, tiling and drainage adds cost but also adds the most value.
- Staircase – where the new stairs land can mean small changes downstairs.
- Roof condition – older roofs may need repair or replacement coverings.
- Finishes – flooring, doors, lighting and decoration choices all move the final figure.
How Long Does a Loft Conversion Take?
Most loft conversions take between 6 and 10 weeks once work starts. Velux conversions are usually the fastest, while mansard and hip-to-gable projects take longer because of the structural changes.
Do You Need Planning Permission?
Most loft conversions fall under your permitted development rights, so full planning permission is not usually needed. Building regulations approval is always required, and we handle that process for you. You can read more in our full Loft Conversion Guide.
How to Keep Your Budget Under Control
Get a detailed written quote after a proper survey, decide your finishes early, and use one experienced contractor who manages the whole job – design, structure, plumbing, electrics and finishing.
Get an Accurate Quote for Your Home
Akaal Construction builds loft conversions across Hayes and West London. Book a free site survey and we will measure up, explain your options and give you a clear fixed price. Call us on 07587 722142 or contact us online.