Roof extensions
London architect guide
Inspiration and ideas
Roof extensions are the most cost-effective way to maximise the floor area of your house or flat when compared to adding the same floor area with a rear or side extension.
As part of this Roof extensions London architect guide we have selected some projects to lend architectural inspiration and design ideas for your roof extension or loft conversion.
You can read here our latest Loft conversion cost planning permission architect guide for everything you need to know about your loft conversion project.
How much value does a .loft conversion add? Please read our advice to Samm Webb as published for Homebuilding & Renovating on March 2023, and click below to read our full advice and guide to homeowners as prepared by George for the purposes of this article: Architect guide – How much value does a loft conversion add.
For more advice and information please see the following:
Royal Institute of British Architects (RIBA)
- Do I need an architect for my extension or home project?
- Why work with an architect?
- How do architects calculate their fees?
Planning Portal
Architect designed bungalow rear and roof extension Stoneleigh KT17 – Loft bedroom garden view
Kitchen extension Highgate Conservation Area N6 House renovation and contemporary design by GOAStudio architects – Green roof
Highgate conservation extensions renovation works to a family home by GOAStudio architects Roof extension
Angel Islington N1 Listed House rear extension – Vaulted roof
Roof extension Chiswick Hounslow W4 – Bathroom by GOAStudio architects
Roof extensions GOAStudio architects London architectural and design home guide
GOAStudio London residential architecture
George Omalianakis, BA (Hons) B.Arch Pg Dip Environmental Design.
Chartered RIBA architect and ARB registered.
RIBA Conservation Registrant specialism in conservation areas, period and Listed buildings.
Residential expert contributor for magazines including Which? magazine and Ideal Home.
Last reviewed by George Omalianakis for GOAStudio: August 2026
Roof extensions London architect guide – Design aspirations and key considerations
Designing the staircase is the single most important thing we will need to consider for any type of roof extension or loft conversion as your roof extensions London architects and experts.
There are Building Regulation restrictions in regards to the risers, goings, and head heights with regards to the staircase. There are fire regulations to consider as well, and plumbing/drainage issues to take into account when an en-suite is to be created.
The design challenge is about how to exercise intelligent space planning around all the relevant restrictions so that both the new loft layout and the layout of the floor below do not get compromised when the staircase is added to the existing floor plan.
Start considering how you would like to use your new space, and how it will interact with the rest of your home. It is important that the new extension blends with the rest of the building and is easily accessible, so when considering the staircase think about its long-term use as much as its style.
Roof extensions London architect guide – Types and options for your home project
There are four main types of loft conversion that might be possible for your property; note that a lot depends on the type of the original roof and the relevant planning policy guidelines for your area.
Dormer window extension
The simplest way of extending your roof area is by adding dormer windows, creating some additional space and bringing light into this area which can form a new bedroom or study.
Partial or full extension of roof at rear
A partial or full extension of the roof at the rear will give you considerably more space should planning permissions allow. A lot also depends on the existing head height in your loft.
The more the maximum head height the more useful a floor area you will be able to add with your roof extension.
Side hip-to-gable roof extension
For detached and semi-detached houses this extension offers significant opportunities for expansion subject to the Permitted Development Rights your property might have.
Mansard roof extension
This is appropriate for properties with what is commonly known as “butterfly” or “V” roofs.
Such roof extensions practically add a full new level to your property and they can be the perfect solution to houses or flats in conservation areas. The planners will take a view on whether a mansard roof can be added.
And here is the rule of thumb when it comes to planning: if the majority of the properties in your terrace have mansard roofs then it is likely the planners will approve an application for a mansard roof to your property.
Your local authority will have restrictions in place about how much you can extend, and part of our job is to achieve the maximum potential for this valuable type of home extension.
For houses with Permitted Development Rights a larger roof extension will be possible, and this is the first thing for us to have a look at before we start the design development process.
Design development stage
During the design development stage we will get to explore lots of ideas, but you can start the process now by considering answers to questions like these:
- “How can we best use this new room? Will it be our new master-bedroom, a study space, a nanny’s room? What other bedrooms are available in the house, and what would work best for our changing needs and family?”
- “Space permitting, how about adding an en-suite, a walk-in wardrobe, or even a coffee area in front of a Juliet balcony?”
- “What do we think about rooflights in the bedroom? They bring more light into the room but how about the rain ticking on the glass, is it charming or just plain annoying?”
After the design and planning stages, our Building Regulations drawings service for house extensions develops the agreed design into coordinated technical information.
Request a free Feasibility Review
If you're not quite sure what’s possible, or whether now’s the right time, we can help you make an informed start.
Send over your address, a few photos, and a short outline of what you're hoping to achieve.
We’ll take a look at your site context, planning history, and potential constraints and respond with early advice tailored to your home and circumstances.
Email us with the subject “Feasibility Review” or send us your information through our Contact us page.
Book a Home Consultation
It is the ideal first step if you are planning works to your home or if you are in the middle of purchasing a property in need of renovation.
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You will come away with a clear sense of your next steps and greater confidence to make informed decisions. The consultation (2hrs, £250 +VAT) is a standalone service with no obligation to proceed.
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Not sure where to start with your renovation or extension?
Read this before you meet an architect, speak to a builder or spend money on drawings.
This free, architect-prepared guide walks you through the 15 essential questions every homeowner should ask before starting a project.
"Should we renovate, extend… or walk away?
15 Questions every London homeowner must ask before starting a project to include homes in Conservation Areas and Listed Buildings."
Whether you're planning a modest rear extension or major alterations to a listed home, it will help you avoid expensive mistakes and give you clarity on what’s possible for your property. Includes guidance on:
Planning approvals. Conservation areas.
Timelines and costs. Appointments you need to make.
Design and sustainability options.
When to press ahead and when to walk away
We provide architectural services for residential projects in the following London Boroughs:
Barnet, Camden, Enfield, Hackney, Hammersmith and Fulham, Haringey, Islington, Kensington and Chelsea, Lambeth, Lewisham, Newham, Tower Hamlets, Waltham Forest, Wandsworth, Westminster
We specialise in
- Greener homes
- Retrofit and energy efficiency for older and traditional buildings
- Conservation areas
- Listed Buildings
- Homeowner architectural services
- Property developments architectural services
GOAStudio London residential architecture limited.
86-90 Paul Street, EC2A 4NE, Hackney
Chestnut Avenue South, E17 9EJ, Waltham Forest
t: 0203 984 3005
