Transform your unused loft into a stunning bedroom, office, or living space. BL Builders are London's trusted loft conversion specialists — fully insured, transparent pricing, and guaranteed quality craftsmanship.
A loft conversion is one of the most valuable home improvements you can make in London. It creates additional living space without the need to extend the footprint of your property — and in London's competitive housing market, it can add 15–25% to your home's value.
At BL Builders, we've completed over 500 loft conversions across London. Our experienced team handles everything from initial design and planning advice through to final finishes — with a dedicated project manager on every build.
All loft conversion types: Velux, dormer, hip-to-gable, mansard & L-shaped
Planning permission advice — many conversions are Permitted Development
Full Building Regulations compliance and sign-off
10-year workmanship guarantee on all structural work
We offer every type of loft conversion to suit your property, budget, and planning requirements across London.
Velux (Roof Light) Loft Conversion
The most affordable option. Velux windows are fitted into the existing roofline — no structural changes required. Ideal for lofts with adequate head height.
From £20,000
Dormer Loft Conversion
The most popular choice in London. A box-shaped extension to the roof that dramatically increases head height and usable floor area.
From £30,000
Hip-to-Gable Conversion
Ideal for semi-detached or detached homes. The sloping hip end is replaced with a vertical gable wall, creating significantly more space.
From £35,000
Mansard Loft Conversion
The most space-maximising option. The entire roof slope is rebuilt with near-vertical walls and a flat roof. Common in Victorian London terrace houses.
From £45,000
L-Shaped Dormer
A rear dormer combined with a hip-to-gable. Creates the maximum possible loft space for Victorian and Edwardian terraced properties in London.
From £40,000
Full-Width Rear Dormer
Extends across the full width of the rear roof slope for maximum floor area. Often combined with a Juliet balcony for additional light and character.
From £38,000
Our Work
Loft Conversion Projects in London
A selection of recent loft conversion projects completed by BL Builders across London.
Rear dormer conversion — Islington, North London
Mansard loft — Clapham, South London
Velux with en-suite — Ealing, West London
Our Process
How Your Loft Conversion Works
From your first enquiry to moving into your new space — here's exactly what to expect with BL Builders.
1
Free Site Survey
We visit your property to assess the loft space, head height, structure, and access. We advise on the best conversion type and whether planning permission is needed.
2
Detailed Written Quote
You receive a full, itemised written quote with no hidden costs. We explain every line — materials, labour, VAT, and any potential extras.
3
Design & Planning
Our team prepares structural drawings and handles any required planning applications or Building Regulations approval on your behalf.
4
Build & Handover
Your dedicated project manager oversees every stage of the build. We keep disruption minimal and hand over a fully signed-off, snagging-free space.
Coverage
Loft Conversions Across All London Boroughs
BL Builders carries out loft conversions throughout all London postcodes and surrounding areas.
Loft conversion costs in London range from £20,000 for a basic Velux conversion to £60,000+ for a full mansard. The average dormer loft conversion in London costs £35,000–£50,000. Prices vary by property type, borough, and specification. We provide a free, itemised quote with no hidden costs.
Most loft conversions fall under Permitted Development rights and don't require planning permission. However, mansard conversions, properties in Conservation Areas, and some London boroughs have specific restrictions. We advise on planning requirements during your free site survey.
A Velux loft conversion typically takes 4–6 weeks. A dormer conversion takes 6–10 weeks. A full mansard or hip-to-gable conversion takes 8–14 weeks. Timelines depend on specification, access, and any planning approval timeframes.
Yes — a loft conversion typically adds 15–25% to a property's value in London. In high-demand postcodes, a well-executed loft conversion can return significantly more than the build cost, making it one of the best-value home improvements available.
Yes. The majority of our London loft conversion projects are completed with the homeowner in residence. We plan the build schedule to minimise disruption, especially during structural work and roof opening stages. Our project manager will keep you informed at every stage.
Free Quote
Get Your Free Loft Conversion Quote Today
Ready to transform your loft? Contact BL Builders for a free, no-obligation site survey and detailed written quote. We cover all London boroughs — response within 2 hours.
