Loft Conversions in London

Outgrown your space or keen to add lasting value to your home? A loft conversion can give you the extra living space you need and save you the hassle and expense of moving. It can also significantly improve your home’s saleability.

How Does Our Loft Conversion Service Work


If you have a loft conversion idea, we can guide you every step of the way. The Red Box team has a wealth of experience gained through a range of projects. We’ve helped residents like you with small loft conversions to create home office space through to major works adding additional bedrooms to their homes.

Converted loft in South West London

Initial Quotation

We visit your property to gain a detailed understanding of your project. We will ask you about your ideas, needs, budgets & timeframe. We transparently price every job so you don’t have any surprises.

Loft Conversion Design

If you already have an architect in place, we will review their design carefully. If not, we can help you with the design work ourselves. In the case of complicated loft conversions, we can even draw up your ideas and provide any required CAD drawings. We can also help you if loft conversion planning permission is required.

Pre-Conversion Survey

Not necessarily. Large or complex conversion projects undoubtedly benefit from an architect, but simpler projects might not require expert input. Depending on your level of confidence, you can undertake the work yourself. Either way, start by contacting Red Box and we can provide wholly independent advice.

Loft Conversion Specialists

As a loft conversion company in London with 17 years+ experience, Red Box has worked in all property types creating new bedrooms, bathrooms, playrooms, studies and great home offices. Sloped ceilings are perfect for storing books.

Whatever style is best for your property – roof light, dormer, hip-to-gable or mansard – as a trusted company, our builders in South West London will ensure you get a finished product that is right for the style of your home and within your budget.

We also specialise in home repairs, bespoke extensions and other building projects – take a look at our gallery for some inspiring examples.

Loft Conversion

Different Loft Conversion Types

There are four main project types – roof light, dormer, hip-to-gable and Mansard. The best style for your home will depend on the type and age of your house as well as your budget.

Many projects are covered by permitted development rights and won’t need planning permission unless you live in specific areas.

A Mansard conversion, however, will nearly always requires planning consent as they change the roof shape and structure.

Roof Light Conversion

What Is A Roof Light Conversion?

A roof light loft conversion (also known as Skylight or Velux) is the simplest type of project. They don’t involve changes to the shape and pitch of the roof.

They simply require skylight windows, a proper floor and a staircase to make the room more accessible. As a result, the cost tends to be less than for a dormer, mansard or hip-to-gable project.

What Is A Hip-To-Gable Conversion?

Hip-to-gable projects are only suitable for semi-detached and detached houses as they need a free sloping side roof. They work by extending the sloping ‘hip’ roof outwards to create a new vertical ‘gable’ wall. This creates valuable extra space for a bedroom, bathroom or home office.

A hip-to-gable project cost is typically higher than for other terraced, detached and semi-detached options as it involves changing the roofline. If you have a detached house with sloping roofs at either end, you have the option of a double hip-to-gable extension.

Hip-To-Gable Conversion
mansard conversion

What Is A Mansard Conversion?

A Mansard extension is the most dramatic and space-making option. This style extension runs the whole length of your home’s roof and features a flat roof, with the back wall sloping inwards at an angle of 72 degrees. Windows are usually fitted within small dormers which extend from the roof to project light into the new space.

Mansard conversions especially appeal to homeowners who want, in effect, to have an extra floor without the hassle of moving. A Mansard extension can be added to the property’s rear or front if permission allows too.

How Much Does A Loft Conversion Cost?

The first questions a client will ask Red Box are always about loft conversion prices. They depend on many factors, from the type of extension you want, to where you live and whether you need planning permission.

The average price of a basic project may cost £20,000-£30,000, however, the final cost will be influenced by the age and style of the property and the type of work you want. On the upper scale, a full double Mansard or dormer conversion, for example, will maximise your upstairs space but will cost more.

Many homeowners across South West London have trusted Red Box to quote for loft conversion work in their homes. Contact us to arrange a visit and we could do the same for you.

Frequently Asked Questions

We have done countless loft conversions in London and have a wealth of knowledge and experience. We have collated some FAQS below.

A nationwide study recently found that adding an extra bedroom and en-suite bathroom through a loft conversion might add an average of 21 per cent to the value of a property. In London, according to another study, the increase could reach 24.5 per cent.

Most conversions will not need planning permission. You will, however, need permission if the converted space exceeds 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached houses. Extensions beyond the plane of the existing roof slope, higher than the existing roof or using different materials might need permission. Homes in areas, including National Parks or Areas of Outstanding Natural Beauty (AONB), might need separate permissions to convert their loft space. Building Regulations will need to be considered too.

Not necessarily. Large or complex conversion projects undoubtedly benefit from an architect, but simpler projects might not require expert input. Depending on your level of confidence, you can undertake the work yourself. Either way, start by contacting Red Box and we can provide wholly independent advice.

The average loft conversion takes between 4 and 8 weeks, however, the actual duration will vary depending on a range of factors including your design and ambitions. We can discuss schedules when we give you a quote.

Why Choose Red Box

We specialise in home improvements, extensions, kitchen fitting and bathrooms as well as the associated services of plumbing, electrical and full decoration work.

Our team work closely with architects and designers, either engaged by us or which you may have already engaged. We are happy to follow your design or work with you on a design to fit your budget and taste.

We’d love to hear from you!

For any questions please fill out the quick form on the right to drop us an email and we will be in touch.

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Kitchen Fitters London

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Very Professional and Great Quality "Red Box carried out a complete renovation and internal restructuring of my home, were hyper efficient, sympathetic to plan alterations, on time and on budget! I have nothing but praise for their work and would thoroughly recommend their work on others." MORE PROJECTS HOUZZ REVIEWS