Specialism
Project type
Insights
Tools

Designing an L-shaped loft conversion the right way [2024 edition]

One of our favourite ways to transform a house is adding an L-shaped dormer - here's what you need to know about them

15 January 2024
5 minutes read
An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.

Adding an L-shaped dormer loft conversion is one of the best ways to increase the space and value of your property, whether you wish to extend the house for your growing family or to create some extra income.

L-shaped loft conversions are a sensible and often fairly affordable way to add that extra space along with value to your property. With successful layout arrangement and beautiful design, your loft could be transformed into a comfortable living space to capture space and light!

Depending on the size of your house, dormer loft conversions can usually increase your existing home by 20-50sqm. Every bit of space under that pitched roof has the potential to be utilised.

This article takes you step-by-step through the process of designing and building your L-shaped loft conversion to add space, comfort and value to your house.

You’ll view examples of great loft conversion projects designed by Urbanist Architecture and an explanation of why they work so well. You’ll also learn how to hire an architect, secure planning permission and stay in control of your dormer loft conversion project.

Let’s jump right in...

Elegant wooden staircase in a newly converted loft, featuring light oak steps, glass side panels, and stainless steel handrails, creating a modern and airy ascent to the upper level of the home, ideal for contemporary interior design.
Designed by Loft Conversion architects at Urbanist Architecture. You can transform your loft into a bedroom, study room, bathroom or whatever you desire!

Why design and build an L-shaped loft conversion?

Your family has grown bigger, you need more space to work from home or that you want to add value to your property to make it more attractive to potential buyers. Sometimes moving to a bigger property just isn’t an option and this is where a good quality loft conversion really comes into its own.

Let’s face it: moving house is an expensive exercise and one of the most stressful experiences you can go through. It can be a serious hit to your bank balance: as well as the cost of the property itself, you’ve got fees, removals and stamp duty. Then the cost of refurbishing your new home can mean costs quickly spiral… That loft conversion to your current home is looking like a better and better option!

An architect-designed loft conversion can add a terrific amount of value to your property as well as maximising space in your home. If you do it right, with care and thought, your loft conversion can be a superb investment as well as a project to remember for you and for your family.

News flash: A quality loft conversion can add four times the value of a brand new kitchen, bedroom or even bathroom to your property. If you ask the experts, they will tell you that a well-designed loft conversion is often top of their buyers’ wish lists and something that they look for in saleable properties.

While there is some initial outlay to get the project off the ground and completed to a high standard; the long-term investment and value added will far outweigh this initial expense and that’s not to mention the extra space that the whole family will benefit from. And when you are ready to up sticks and move on, you’re virtually guaranteed to sell at a higher price than you paid and bank yourself some tidy profit.

An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
Designed by Loft Conversion architects at Urbanist Architecture

What is an L-shaped loft conversion?

An L-shaped dormer conversion is where two dormer builds are constructed in a way that they join together. Usually one dormer will be built on the rear outrigger roof and the other on the main roof, which is what gives it the instantly recognisable L-shape.

The shape itself means that L-shaped dormers are only suitable for certain types of property, mainly either Edwardian or Victorian properties where there is an existing wing  at the rear, known as a two-storey outrigger. This type of build is a great way to get some more space out of a property like this especially if you own a mid-terrace property.

How to design a loft that’s bright, airy and welcoming

Here’s the most important part: loft conversions have to be treated as more than just a box on a roof. They should be a successful addition that makes a real difference to your property. They have to be light and airy –  the good news is that this is easily achieved as you have so much roof space to deal with and therefore the potential for masses of natural light.

You can channel so much light without the need for wide skylights – a small aperture on the roof can give you the same quality and depth of light as a far larger opening (like a window) on the side of a property. In terms of natural light, the world is your oyster when it comes to loft conversions as they can be absolutely flooded with light.

With so much natural light at your disposal, your new loft space will appear so much bigger and more spacious than it actually is.

For more tips on designing a loft conversion, have a read of our Ultimate Loft Conversion Design & Planning Guide.

Bright and modern loft bathroom with a freestanding bathtub, a large window with a view of the trees, minimalist wooden vanity with a round mirror above it, and a walk-in shower enclosed by glass panels, showcasing a contemporary design with geometric green tiles.
Designed by Loft Conversion architects at Urbanist Architecture. this picture above shows the interior of an L-shaped dormer with en suite facilities. A great example of smart design and use of space.
Luxurious minimalist bathroom in a loft conversion featuring a sleek freestanding bathtub near large windows with a view of greenery, accompanied by a black heated towel rail and a vibrant green stool, creating a serene and stylish spa-like atmosphere.
Designed by Loft Conversion architects at Urbanist Architecture. this loft example above shows a free standing bath in an L-shaped dormer loft conversion with en suite facilities. Proof that loft conversions don’t have to be pokey, dark and lacking in style.
Contemporary loft bathroom designed with pastel pink walls and modern fixtures, featuring a wooden vanity with a large round mirror, white ceramic toilet, and a view into a cosy bedroom, creating a seamless flow from personal care space to private living area.
Look at all of that space! When done right, an L-shaped dormer loft conversion can deliver a huge amount of space and this is great example of natural light making the space even more spacious! Loft conversion with a large bathroom and master bedroom, designed by Urbanist Architecture.

How much does an L-shaped loft conversion cost?

We’re going to be honest: an L-shaped loft conversion is not the cheapest option – but remember it will add value to your home. What you are paying for is technical structural work – the roof needs to be removed and then rebuilt. You will need an architect and you may need planning permission depending on the limitations of permitted development rights, so factor in these costs and time constraints. The best L-shaped dormer loft conversion price you’ll get for a job like this in London is £50,000 but realistically you will be looking at least £70,000.

Modern loft bedroom with pastel blue walls and a large skylight flooding the room with natural light, featuring sleek built-in wardrobes in ivory and a minimalist aesthetic, offering a serene and organised living space in an urban home.
This master bedroom could be in any part of the house, but it’s in an L-shaped dormer loft conversion. Stylish, contemporary and spacious. Master bedroom in loft conversion with built-in wardrobe designed by Loft Conversion architects at Urbanist Architecture.

Will I need planning permission for an L-shaped loft?

Most L-shaped loft conversions are covered under permitted development rights, which means that you won’t require planning permission. There are exceptions: if the house is in a conservation area, for instance, or is a listed building, you will have to make a planning application. You will also need to make one if your conversion is higher or wider than the existing roof, or if it is more than 40 cubic metres (terrace house) or 50 cubic metres (other properties).

Our advice is, as ever: check. Ask your local council’s planning department or if you are using an architect, they will be able to tell you if you need to apply.

You should also know that you will need building regulations approval even if your works are covered by permitted development rights. And you may well need to make a Party Wall Agreement with your neighbours.

Open documents displaying detailed planning permission guidelines for roof additions, with a focus on conditions and specifications for Class B developments, illustrated with text and a diagram, providing crucial information for homeowners planning to extend their roof space.

How can I get an L-shaped extension without the hassle?

In order to avoid any loss of cash, hassle and headaches, contact an architect who specialises in loft conversion projects to achieve the most out of your property. Your architect will not only prepare drawings, design your loft conversion and obtain the necessary approvals for you but also will assist you to find a competent builder and then manage the project for you.

Document from Harrow Council on a gray background, detailing the grant of a Certificate of Lawful Use for a proposed development by Urbanist Architecture, showcasing official planning permission paperwork essential for legal property modifications.
Certificate of Lawfulness: Lawful Development Certificate Loft Conversion secured by Urbanist Architecture
Open engineering design document on a dark textured surface, displaying detailed structural calculations and beam load diagrams for a loft conversion project, indicating meticulous planning and analysis by Urbanist Architecture to ensure safety and integrity in building construction.
Building Regulations Structural Calculations for a Loft Conversion by Urbanist Architecture
Modern L-shaped dormer loft conversion featuring a stylish reading nook with a blue velvet chair by a floor-to-ceiling window offering a view of tall trees, complemented by built-in light gray shelves and wood flooring, creating a serene and inviting space in an urban home.
An L-shaped dormer loft conversion can offer you flexibility as this multi-functional space demonstrates. You get to dictate the use and function of the space as and when you need it. Designed by Urbanist Architecture.

How Urbanist Architecture can help You

Urbanist Architecture is a London-based RIBA chartered architecture and planning practice with offices in Greenwich and Belgravia. With a dedicated focus in proven design and planning strategies, and expertise in residential extensions, conversions and new build homes, we help homeowners create the homes they have always dreamed of and landowners and developers achieve ROI-focused results.

If you would like us to help you with your loft conversion, please don’t hesitate to get in touch. Contact us now.

Yuki Terado, Architectural Designer at Urbanist Architecture
AUTHOR

Yuki Terado

Yuki is in the final stretch of her qualifications as an architect. She has experience of projects from feasibility through to technical design, Her areas of professional knowledge include interior design, the licence-to-alter process and office-to-residential conversions.

Send me a message
Or call me on
020 3793 7878

Write us a message

We look forward to learning how we can help you. Simply fill in the form below and someone on our team will respond to you at the earliest opportunity.

Have you considered how much the construction will cost?

Urbanist Architecture is committed to protecting your privacy, and we'll only use your information to deliver the services you requested. For more information, please review our privacy policy.

Some fields are incorrect.

Read next

The latest news, updates and expert views for ambitious, high-achieving and purpose-driven homeowners and property entrepreneurs.

Read next

The latest news, updates and expert views for ambitious, high-achieving and purpose-driven homeowners and property entrepreneurs.

Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
BIM process: Ultimate guide by BIM architects for developers and homeowners
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
Getting planning permission for side extensions on semi-detached houses
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
Designing modern care homes and revolutionising retirement living
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
Powerful tips to design and get planning permission for build-to-rent schemes in London
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
New use class order 2020: Use Class E and the key changes explained [2024 update]
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
The architect's guide to extending and refurbishing a Victorian house
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
The consequence of altering or extending a listed building without planning
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
Why a chartered architect is a must-have for your project
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
Designing an L-shaped loft conversion the right way [2024 edition]
Read more
Image cover for the article: An L-shaped dormer loft conversion on a Victorian terraced house, showcasing modern windows and slate roof against the traditional brickwork, exemplifying a seamless blend of contemporary design with classic architecture in an urban setting.
Virtual reality in architecture: Visit your home before it’s been built with VR
Read more

Ready to unlock the potential of your project?

We specialise in crafting creative design and planning strategies to unlock the hidden potential of developments, secure planning permission and deliver imaginative projects on tricky sites

Write us a message
Decorative image of an architect working
Call Message