Loft Conversion London: Costs, Types & Planning Guide 2026
A loft conversion in London can add valuable living space without moving home, but the cost and planning requirements depend on the conversion type, property and location. Typical options include Velux, dormer, hip-to-gable and mansard conversions. This guide explains loft conversion costs, planning permission, Building Regulations, timescales and the process for London homeowners.
Loft Conversion London at a Glance
| Question | Quick Answer |
|---|---|
| How much does a loft conversion cost? | Cost depends on the conversion type, size, specification and property. |
| Do I need planning permission? | Some loft conversions may fall under permitted development, while others require planning permission. |
| Are Building Regulations required? | Yes. Loft conversions must comply with applicable Building Regulations. |
| How long does it take? | A typical project can take several months from design through completion. |
| What are the main types? | Velux, dormer, hip-to-gable and mansard. |
| Can ERD Ltd handle planning and construction? | ERD Ltd provides design, planning, construction and project support. |
How Much Does a Loft Conversion Cost in London?
The cost of a loft conversion in London depends on the conversion type, property structure, floor area, structural work, specification, access and planning requirements. Use the figures below as a starting guide rather than a fixed quotation.
| Loft Conversion Type | Typical Guide Cost |
|---|---|
| Velux loft conversion | £15,000–£25,000+ |
| Dormer loft conversion | £35,000–£65,000+ |
| Hip-to-gable conversion | £45,000–£75,000+ |
| Mansard loft conversion | £60,000–£100,000+ |
Loft Conversion in Hounslow and West London
ERD Ltd provides loft conversion services from its base in Hounslow, Middlesex, helping homeowners across West London with loft design, planning, structural work and construction. We work with different property types and can advise on the most suitable conversion based on your roof structure, available space, budget and planning requirements.
Why Homeowners Choose Loft Conversions
Loft Conversion London projects have surged in popularity for several compelling reasons. London’s housing market continues to place enormous pressure on families and professionals seeking more space. Moving to a larger property in Greater London comes with substantial stamp duty, estate agent fees, and removal costs — often totalling tens of thousands of pounds. By contrast, converting your existing loft is frequently the most cost-effective route to gaining a sizeable new room without the upheaval of relocation.
Several trends are driving demand even further in 2026. The continued rise of hybrid and remote working has made the home office a near-essential feature in modern properties. Meanwhile, changing family structures mean that multi-generational living arrangements — where parents, children, and grandparents share one home — are becoming more common across boroughs like Hounslow, Ealing, Islington, and Hackney. A thoughtfully designed loft conversion can accommodate all of these needs.
Types of Loft Conversion
Loft Conversion London projects are not one-size-fits-all. The right type depends on your property’s structure, roof pitch, local planning constraints, and budget. Here are the most common options our clients opt for:
1. Velux Loft Conversion
The simplest and most affordable type, a Velux conversion involves installing roof windows into the existing roof slope without altering its structure. It typically does not require planning permission and is ideal for properties in conservation areas. Costs start from around £15,000 to £25,000 in London. The trade-off is that headroom is limited by your existing roof pitch.
2. Dormer Loft Conversion
By far the most popular Loft Conversion London style, a dormer extends the roof vertically to create additional floor space and headroom. It suits most terraced, semi-detached, and detached properties. A standard rear dormer typically falls under permitted development rights, meaning no formal planning permission is needed. Costs in London range from £35,000 to £65,000 depending on size, finishes, and borough.
3. Hip-to-Gable Loft Conversion
Popular with end-of-terrace and semi-detached properties, a hip-to-gable conversion restructures the hipped (sloped) side of the roof to create a vertical gable wall, dramatically increasing usable space. Often combined with a rear dormer for maximum floor area. London costs typically range from £45,000 to £75,000.
4. Mansard Loft Conversion
A mansard conversion is the most extensive and expensive type, involving a near-vertical rear wall and a near-flat roof. It delivers the largest possible floor area and is frequently seen in central and inner London boroughs where Victorian terraced houses are common. Planning permission is almost always required. Expect costs in the £60,000 to £100,000+ range in London.
Loft Conversion Planning Permission & Building Regulations
Whether you need planning permission for a loft conversion depends on the proposed design, your property and any restrictions affecting it. Some loft conversions can be carried out under permitted development rights, while others require a full planning application.
When a Loft Conversion May Fall Under Permitted Development
For qualifying houses, permitted development rules can allow additional roof space of up to 40 cubic metres for terraced houses and 50 cubic metres for detached or semi-detached houses, subject to the applicable conditions and restrictions.
When Planning Permission May Be Required
Planning permission may be required where the proposed conversion does not meet permitted development conditions, or where additional restrictions apply to the property.
Before starting work, homeowners should check the requirements for their specific property and local planning authority.
For homeowners in Hounslow and West London, the planning position should be checked against the specific property, because local restrictions, conservation areas and property status can affect what is permitted.
How Long Does a Loft Conversion Take?
Loft Conversion London timelines depend on the scale and complexity of the project, but here is a general guide to what you can expect at each stage:
| Stage | Typical timeframe |
|---|---|
| Initial survey and feasibility | 1–2 weeks |
| Architectural design | 2–4 weeks |
| Structural calculations | 2–4 weeks |
| Planning, if required | Around 8–10 weeks* |
| Building regulations | 2–4 weeks |
| Construction | Around 6–10+ weeks |
| Final inspection and sign-off | 1–2 weeks |
A straightforward loft conversion may take around three months of project work, while projects requiring planning, more extensive structural work or higher specifications can take several months from initial design to completion.
How to Choose a Loft Conversion Company
Loft Conversion London is a specialist discipline that combines architectural design, structural engineering, carpentry, roofing, insulation, plumbing, and electrical work. Choosing the right company to manage all of these disciplines is the single most important decision you will make. Here is what to look for:
- Proven local experience: Choose a contractor with a strong portfolio of completed loft conversions in London — ideally including projects in your borough or with a similar property type.
- Full project management: Avoid the stress of coordinating multiple subcontractors yourself. A reputable company like ERD Ltd handles everything from design and planning applications through to the final building control certificate.
- Transparent, itemised quotes: Never accept a vague lump-sum quote. Insist on a detailed breakdown of labour, materials, and all associated fees.
- References and reviews: Ask for contact details of past clients and check independent review platforms for honest feedback.
- Insurance and accreditations: Ensure the company holds valid public liability insurance and, where applicable, relevant trade body memberships.
- Clear contract: Your agreement should specify the scope of works, payment schedule tied to project milestones, a defined completion date, and a defects liability period.
Why Choose ERD Ltd for Your Loft Conversion?
Loft Conversion London homeowners have trusted ERD Ltd — Evolve Renovations & Developments Ltd — to deliver outstanding results across the capital. Based in Hounslow, Middlesex, we serve clients throughout Greater London and the Home Counties, specialising in high-quality residential loft conversions, house extensions, full home renovations, kitchen remodels, bathroom transformations, and more.
Our loft conversion service is truly end-to-end. We begin with a free site survey and feasibility assessment, advise on the best conversion type for your property and budget, and provide a detailed, no-obligation quotation. Our experienced in-house team handles architectural drawings, structural calculations, planning applications, building regulation submissions, all construction works, and the final building control sign-off — giving you a fully warranted, legally compliant new living space without the administrative burden.
We take enormous pride in the quality of our finishes. From bespoke joinery and fitted wardrobes to luxury en-suite bathrooms and full electrical fit-outs, every element of your new loft is built to last and designed to impress. Our project managers maintain daily communication with clients, provide photographic progress updates, and ensure the site is kept clean, safe, and respectful of your daily life throughout the build.
Loft Conversion vs House Extension: Which Is Right for Your Home?
A loft conversion uses existing roof space to create additional accommodation, while a house extension increases the footprint of the property. The right option depends on your available loft space, garden area, planning constraints, budget and the type of room you want to create.
| Loft Conversion | House Extension |
|---|---|
| Uses existing roof space | Increases property footprint |
| Can add bedrooms/offices | Can add kitchens/living areas |
| No garden space required | Usually uses part of the garden |
| Structural roof work required | New foundations may be required |
| Planning depends on design | Planning depends on design |
Planning a Loft Conversion in Hounslow or West London?
Thinking about converting your loft? ERD Ltd can help you assess your available space, understand planning requirements, explore suitable conversion options and plan the construction process. Contact our Hounslow-based team to discuss your project and request a quotation.
Written by: ERD Ltd
Last updated: September 2026
Loft Conversion London FAQs
Do I need planning permission for a loft conversion?
Not always. Some projects may qualify for permitted development rights, while others require planning permission depending on the design, property and restrictions affecting it.
How much does a loft conversion cost in London?
Costs vary according to conversion type, size, structural requirements, specification and property. Use current project-specific quotations rather than treating online guide prices as fixed costs.
How long does a loft conversion take?
A typical loft conversion can take several months from design through completion, although straightforward projects can be quicker and complex projects can take longer.
What is the most common type of loft conversion?
Dormer conversions are widely used because they can create additional floor area and headroom, but the appropriate option depends on the property and planning constraints.
Can a loft conversion add a bathroom?
Yes. A loft conversion can incorporate an en-suite or bathroom where the design, plumbing, drainage, ventilation and Building Regulations requirements can be accommodated.
Do loft conversions need Building Regulations approval?
Yes. Loft conversion work needs to comply with applicable Building Regulations, including requirements relating to structure, fire safety, insulation, ventilation and stairs.
Can ERD Ltd manage the whole loft conversion?
ERD Ltd can provide support across design, planning, structural requirements and construction, depending on the project scope.