Roof extensions | London

Architect designed house extension Chiswick Hounslow W4 – Bathroom design photos Roof extensions in London | Home ideas

A guide to roof extensions 

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.


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 aspirations 

Designing the staircase is the single most important thing we will need to consider for any type of roof extension or loft conversion. 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.

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?”

Inspiration and ideas

Below we have selected some projects to lend architectural inspiration and design ideas for your roof extension or loft conversion. Enjoy!

purplebox Roof extensions in London | Home ideasVisit our portfolio for a selection of case studies or alternatively visit our London Residential page for your local authority and information about planning.

Awards + Achievements

logobar4 1 Roof extensions in London | Home ideas
squares 2 Roof extensions in London | Home ideas squares 3 Roof extensions in London | Home ideas squares 4 Roof extensions in London | Home ideas google plus Roof extensions in London | Home ideas

GOA300 Roof extensions in London | Home ideas

We see ourselves as creative problem solvers who will deal with any construction, planning, and design issues relevant to your project.

Contact Details

Kemp House | 152 - 160 City Road | EC1V 2NX | Islington

Grove Mews | W6 7HS | Hammersmith and Fulham

t: 020 3693 3817


ARB e1478972573319 Roof extensions in London | Home ideas RIBA Roof extensions in London | Home ideas

Click on the map to find a project in your area

rectangle map GOA Roof extensions in London | Home ideas

Website | Blackledge & Sandall

Creative Director | Umi Ishimoto