Loft Conversions in London
Add a bedroom, bathroom, or home office without moving house. We deliver every type of loft conversion across London — fixed price, Building Regulations managed, structural warranty included.
L-shaped dormer · East London
2 bedrooms + en-suite added. Fixed price. 11 weeks.
Why convert your loft?
Add 20–25% to property value
A well-designed loft conversion is one of the highest-return home improvements in London — typically adding more value than it costs.
No planning permission needed in most cases
Most dormer and hip-to-gable conversions fall under permitted development rights, meaning no planning application — just Building Regulations approval.
Avoid the cost of moving
Stamp duty, legal fees, and moving costs on an average London home typically exceed £30,000. A loft conversion gives you the space for less.
Types of loft conversion we deliver
The right conversion type depends on your roof, property type, and what you want to achieve. We advise on the best option at the free survey.
Dormer loft conversion
The most popular loft conversion type in London. A dormer extends vertically from the existing roof slope, creating a flat-roofed extension that adds full-height usable floor space. Ideal for terraced and semi-detached houses. Often falls within permitted development rights.
Best for: Terraced, semi-detached, and detached houses
Hip-to-gable loft conversion
Converts a hipped (sloped) roof end to a vertical gable wall, combined with a rear dormer. Creates significantly more usable floor space than a dormer alone. Common on 1930s semi-detached houses across East and South London.
Best for: Semi-detached and end-of-terrace houses with hipped roofs
L-shaped dormer loft conversion
An L-shaped dormer wraps around the main roof and the back addition roof, creating a very large loft footprint. The most space-efficient option for Victorian and Edwardian terraced houses with a back addition. Can accommodate two bedrooms and a bathroom.
Best for: Victorian and Edwardian terraced houses with a rear outrigger
Mansard loft conversion
A mansard conversion alters the roof structure to create near-vertical rear walls at approximately 72 degrees, maximising internal headroom across the full floor plate. Most common in Conservation Areas and period properties. Usually requires full planning permission.
Best for: Period properties, Conservation Areas, or where maximum space is needed
Velux / roof light conversion
The most cost-effective conversion type. Velux windows are installed into the existing roof slope with minimal structural change. Suitable where the existing roof already has adequate head height. No change to the roof line, so typically permitted development.
Best for: Properties with adequate existing head height and no planning restrictions
Loft conversion costs in London (2026)
| Conversion type | Typical cost range | What's included |
|---|---|---|
| Velux / roof light | £28,000–£42,000 | Structural floor, Velux windows, insulation, stairs, plaster, electrics |
| Single dormer | £38,000–£55,000 | As above plus dormer structure, flat roof, casement windows |
| Hip-to-gable + rear dormer | £48,000–£70,000 | Gable end rebuild, rear dormer, full floor, stairs, M&E first fix |
| L-shaped dormer | £55,000–£80,000 | Double dormer structure, larger floor plate, bathroom rough-in included |
| Mansard | £70,000–£100,000+ | Full roof rebuild, near-vertical rear wall, maximum headroom across full floor |
Figures are guide ranges for London 2026. Final price depends on your property, specification, and access. Second-fix materials (sanitaryware, flooring, lighting) are client-supplied unless otherwise agreed. RCB does not install carpet.
How we deliver your loft conversion
Free feasibility survey
We visit your property, measure the existing roof structure, check head heights, assess the stair access options, and confirm which conversion type is most suitable. We'll also advise on planning requirements and likely Building Regulations involvement. No obligation.
Design and planning
Where planning permission is required, we coordinate with our architectural partners or your architect to prepare drawings for submission. For permitted development schemes, we prepare the technical drawings needed for Building Control submission directly.
Structural design
A structural engineer designs the new floor structure (typically engineered joists), specifies any steel or timber beams, and calculates the loading on the existing structure. We coordinate this as part of the pre-construction package.
Fixed-price contract
You receive a detailed, itemised scope of works and a fixed price before any work starts. We confirm start and finish dates. No surprises — agreed variations are documented in writing before any additional work begins.
Delivery
Our site team manages the full conversion sequence: scaffold, structural floor upgrade, roof alterations, dormer construction, waterproofing, insulation, windows, first-fix, plaster, second-fix, stairs, and decoration. You have a single point of contact throughout.
Building Regulations sign-off
All loft conversions require Building Control approval and inspection. We manage the notification, stage inspections, and final sign-off. You receive a completion certificate — essential for the sale of your property in future.
Common questions about loft conversions
Do I need planning permission for a loft conversion in London?
Most dormer and hip-to-gable conversions in London fall under permitted development rights and do not require a planning application. However, properties in Conservation Areas, listed buildings, and some converted flats are excluded. We assess this at the free survey and confirm which route applies before any cost or commitment.
Does a loft conversion always need Building Regulations approval?
Yes — all loft conversions require Building Regulations approval regardless of planning status. This covers structural calculations, fire safety (including escape windows and fire doors), thermal insulation, and stair compliance. We manage the full Building Control process as part of the project.
How long does a loft conversion take?
Most loft conversions take 8–14 weeks on site depending on the type and complexity. Velux conversions are typically 6–8 weeks; L-shaped dormers and hip-to-gable schemes are 10–14 weeks. We provide a detailed programme before work starts.
Will I need to vacate my home during the conversion?
In most cases, no. Loft conversions are managed to allow normal occupancy throughout. The main disruption periods are scaffold erection, roof opening, and stair installation. We discuss the specifics of your project at the survey.
Is a loft conversion cheaper than an extension?
Generally yes — a comparable amount of usable floor space costs less via a loft conversion than a ground floor extension, largely because foundation and drainage works are not required. However, the two project types serve different needs, and we can help you compare options if you're undecided.
Can I add a bathroom to my loft conversion?
Yes — most of our loft conversions include at least an en-suite. The plumbing and drainage are routed during the build. We coordinate the first-fix plumbing as part of the contract; bathroom fixtures and fittings are client-supplied and we install them.
Loft conversions by area
Useful guides
How much does a loft conversion cost in London?
Realistic cost breakdown by conversion type — dormer, hip-to-gable, Velux and mansard.
Hip-to-gable loft conversion — cost and planning
Everything you need to know if your semi-detached house has a hipped roof.
Building Regulations for house extensions
What gets inspected, why it matters, and how to get your completion certificate.
Does a loft conversion add value in London?
ROI figures, which conversion type adds the most, and what affects the return on your investment.
Do you need planning permission for a rear extension?
Permitted development limits, Prior Approval, and when you need a full application.
Get a free loft conversion survey
We visit your property, confirm what's possible, and give you a clear fixed price — no obligation, no pressure. Evenings and weekends available.
Or call us on 07359 872594