LET-HD Developments is a London loft conversion specialist. We handle every stage of your project in house, from the first survey and structural design through planning and building control to the finished room, so you deal with one team from start to finish.
A loft conversion is one of the most cost-effective ways to add space to a London home. It uses the space you already own, adds a bedroom or bathroom without touching the garden, and typically increases the value of your property by up to 20%.
We work across London and the surrounding areas, including Hackney, Islington, Walthamstow, Wanstead, Woodford, Ilford, Romford and Stratford.
Why convert your loft?
- Turn unused roof space into a valuable asset.
- Add a bedroom, en-suite or study without giving up garden space.
- Expand your home without the cost and disruption of moving.
- Make your home more spacious in a cost-effective way.
- Add up to 20% to the value of your house.
Types of loft conversion
We build all five main types. The right one for you depends on your roof shape, the headroom available and how much space you need.
Velux / rooflight
Windows fitted into the existing roof slope, with the loft insulated and boarded out. The simplest and lowest-cost option where the loft already has enough headroom.
Rear dormer
The most popular conversion in London. A box is built out of the rear roof slope to create full headroom and vertical walls across most of the room. Usually permitted development.
Hip-to-gable
Rebuilds a sloping hip end as a vertical gable wall, often combined with a rear dormer. Ideal for semi-detached and detached homes with hipped roofs, and usually permitted development.
L-shaped dormer
Two dormers — one over the main roof and one over the rear addition (outrigger) — giving two rooms plus a bathroom. Common on Victorian terraces.
Mansard
The rear roof slope is rebuilt at a steep pitch with a near-flat top, creating the most floor space and ceiling height. The standard option in many conservation areas, and always needs planning permission.
Our process
Free survey and quote
We visit, check the roof structure and headroom, and give you a clear written quote.
Design and structural calculations
We prepare the drawings and, where needed, structural calculations for building control.
Planning and building control
We advise whether your project needs planning permission and handle the building control application.
Build and weatherproof
Scaffolding, roof work, steels and the dormer are completed and made weathertight.
First fix, second fix and finish
Electrics, plumbing, insulation, plastering, staircase and decoration, through to sign-off.
Do you need planning permission?
Most rear dormer and hip-to-gable loft conversions in London are covered by permitted development, which means no planning application is needed, as long as the added roof volume stays within the limits (around 40m³ for a terraced house and 50m³ for a semi-detached or detached house).
You will usually need planning permission if your home is in a conservation area or under an Article 4 direction, if you are proposing a mansard, or if you have already used your permitted development allowance on another extension.
Every loft conversion needs building regulations approval, whether or not planning permission is required, and the Party Wall etc. Act 1996 applies to loft work on terraced and semi-detached homes. We explain exactly what applies to your property at the survey stage.
What does a loft conversion cost in London?
Costs depend on the type of conversion, the size of the loft and the specification you choose. As an indicative guide to 2026 London prices:
| Conversion type | Indicative build cost | Typical space added | On site |
|---|---|---|---|
| Velux / rooflight | £30,000 – £50,000 | Limited | 4–6 weeks |
| Rear dormer | £45,000 – £80,000 | 15–20m² | 6–10 weeks |
| Hip-to-gable with rear dormer | £55,000 – £90,000 | 18–25m² | 8–12 weeks |
| L-shaped dormer | £55,000 – £95,000 | 20–25m² | 10–12 weeks |
| Mansard | £65,000 – £120,000+ | 25–35m² | 12–14 weeks |
These figures are indicative 2026 London build costs and exclude architect, planning, party wall and building control fees. Your free, no-obligation quote will be specific to your property and specification.
Why choose LET-HD
- One team, start to finish. We manage design, planning, building control and the build.
- Experienced and accredited. We are an established London builder and a member of recognised trade bodies (see our accreditations).
- Quality guaranteed. All our work is carried out by our own skilled tradesmen and is fully insured.
- Clear pricing. A detailed written quote, with no hidden extras.
See our loft conversions
You can see examples of our completed loft conversions and refurbishments on our Our Work page.
Frequently asked questions
How long does a loft conversion take?
Most rear dormer and hip-to-gable conversions take six to ten weeks on site once drawings and building control approval are in place. Mansards and more complex projects take longer.
Can I stay in my home during the work?
Yes. Because the work is largely confined to the roof and one staircase run, most clients stay living in the house throughout.
Do I need an architect?
You need drawings and, for most projects, structural calculations. We can manage this for you, or work with your own architect if you prefer.
Will a loft conversion add value?
A well-built loft conversion can add up to 20% to the value of your home, and adds a bedroom or bathroom without reducing your garden.
What areas do you cover?
We cover London and the surrounding areas. If you are not sure whether we work in your area, just call us on +44 (0) 203 355 5313.
Related guides
- Do you need planning permission for a loft conversion in London?
- Party wall agreements: a guide for London homeowners
- How much does a loft conversion cost in London? (2026)
- How much value does a loft conversion add?
Get a free loft conversion quote
Call +44 (0) 203 355 5313, email info@lethd.com, or use our contact form. We will arrange a free survey and give you a clear, written quote.