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Open season: 4 of the best glass-backed extensions

We all want more light and space in our homes and the big trend right now is to get it by blurring the boundaries between inside and out with a glass-backed extension. We take a look at some case studies...

view of garden from extension
Ben Anders

We asked homeowners and architects to share their top tips and learnings:


Photographer Ben Anders’ home in East Dulwich, London, has been dramatically improved with the addition of large folding doors that open in a concertina fashion, connecting his kitchen to the garden. Here, he shares the ups and downs of the project.

kitchen with garden
Ben Anders

Why did you choose folding doors? We have a relatively small garden, so to increase the feeling of space in the summer we wanted doors that could open fully, turning the outdoors and the kitchen into one large living area.

What did the build involve? As we weren’t extending the footprint of the property by much, the project was completed under permitted development rights [this means Ben didn’t need planning permission. Ask your architect to see if your project complies and see planningportal.co.uk for more info]. We did have to get a party wall agreement with our neighbours [see What to know before you build, p71], but thankfully they agreed with our plans. It’s so important to keep on side with your neighbours during a big build.

kitchen interior
The blend between in and out is seamless, thanks in part to a consistent colour palette inside and out (try Farrow & Ball’s ‘Off Black’ for a similar wall colour), plus seamless poured concrete flooring throughout
Ben Anders

Were there any problems you had to overcome? The main issue we had was building over a Thames Water pipe. You have to apply for permission to do this and pay the water utility company a fee [starting from £299]. We only found out that there was a pipe once excavation work had started, so this delayed the project by a few weeks. If we had known, we would have applied for the permission to build over it during the planning stages.

Is there anything you would change? In this house bi-folding doors are the perfect solution, but I love Crittall’s steel-framed windows, so we might use them in the future. A project like this is going to be stressful at times, and there will always be surprises along the way, but the result is well worth it.


Looking for a smaller project that will have a big effect? Use folding window panes to welcome your garden indoors. Here, architect Henri Bredenkamp of Studio 30 and homeowner Helen talk about the difference they made to Helen’s west London townhouse.

kitchen table
Studio 30 Architects

Why did you choose these windows? Henri: Bi-folding windows open in a way that doesn’t block or obscure your view of the garden at all – some have chunky head tracks and side jams, but you can cleverly hide these within the window frame if you plan in advance.They break down the barriers between the inside and outside. Those few summer days that the owners get to fully open their windows make the whole build worthwhile.

What did the project involve? Henri: The process was turned around, from survey to final installation, in three to four weeks. For a fairly standard 4.5-metre by 2.5-metre five-panel window with a powder-coated aluminium frame (essential for weatherproofing)you can expect to spend between £5,000 and £7,000, including VAT and installation. But, when it comes to buying the windows, don’t just go for the cheapest option, and never go for uPVC! Keep in mind that this is a long term investment.

‘A well-designed glass extension will enhance family life, creating a room that everyone gravitates’

How has it improved your home? Helen: So many Victorian terraces are dingy and sad during the colder months, but this large expanse of glass has completely changed the outlook for us. We can soak up the winter sun while we’re inside. It’s bright, warm and open.

Is there anything you would change? Helen: I’d swap the roof light for one that we can open to get even more fresh air into the kitchen. Next time, perhaps. studio30architects.co.uk/


Architect Patrick Michell reveals exactly how he transformed his dark, narrow terraced house into a bright, modern home with a clever side extension.

extension with glass roof light
Sam Peach

Why did you choose this sort of extension? L-shaped Victorian terrace houses generally have very well-proportioned front rooms but narrow kitchens to the rear, with poor access to the garden. A glass side extension increases both the size and the overall brightness of the whole back of the property.

kitchen outdoor
This glass-walled side extension has brought light, space and contemporary style to the narrow kitchen in this Victorian terrace
Sam Peach

What does building one involve? The initial design takes two to three months, and you should set aside eight are particularly complex projects from a planning perspective as they often require Party Wall Awards and build-over licenses for the underground drainage [if you are building over or within three metres of a public sewer you’ll need to apply to your water provider for permission and pay upwards of £299]. Construction takes eight to 12 months, depending on the complexity of the project. In London, side extensions generally cost around £125,000 plus VAT for the construction work.

extension with glass rooflight
Sam Peach

How has it improved your home? Watching the morning light come in and enjoying a fantastic view out onto the garden has definitely given me a sense of joy. The extension has transformed the traditional dark, narrow rear wing of the house into the best part of
my home. Even rainstorms become an event when you have a glass roof. platform5architects.com/


One name springs to mind when you see these industrial-look windows and that’s Crittall. This heritage firm has seen a surge in popularity of late. Here Alan West, design director of glass extension specialist Trombé Ltd, discusses the enduring appeal of steel and talks us through this striking side and rear extension project.

crittall windows
This side and rear extension features Crittall steel-glazed windows and doors. The British firm is the original maker of this type of window, which has an industrial yet art deco look

Why are Crittall windows so popular? Beloved of interiors fans and architects, these art deco-style steel-framed windows (the company also sells sliding doors) usually have a striking black edge, although other colours are available. The overall effect is very appealing – bright, light spaces and a well-designed glass extension create a room that everyone gravitates towards. The windows used in this property are particularly detailed, with a multitude of glazing bars, but Crittall windows can also be simpler and more modern in appearance.

crittal windows extension

What would this build involve? The build time for a project like this one is generally between 12 and 20 weeks, depending on the size of the building. The cost of the project pictured here would have been in the region of £75,000 – you can produce a similar effect by spending upwards of £20,000, not including builder’s fees. Most extensions require planning and if you are building within a metre of a party wall, then a Party Wall Award will be required – don’t be afraid of these processes, as they’re there to protect you as much as your neighbour!

crittall window extension

Are there any downsides to a glass side extension? There’s a great deal of ill-informed opinion on glass extensions – the classic being that they make your home too hot in summer and too cold in winter. Don’t let this put you off! There are loads of solutions to address both of these issues, such as high-performance double glazing – glass that cleverly reflects solar heat while retaining internal heat (trombe.co.uk).

This article appeared in the September 2016 issue of ELLE Decoration.

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