Glass extension ideas

Wanting to gain more floor area is an obvious reason to extend – but what about the other benefits? More natural light streaming in, for example, is one of them, and one that shouldn’t be underestimated.

What is a glass extension?

A glass box extension is a popular architectural feature, which helps brighten your home. With glass walls and roof, and little or no frames, there are no obstructions that could limit the amount of sun streaming in. This way, you not only open up your space, but you also have a whole range of new design opportunities.

From skylights and glazed doors to entirely frameless glass boxes, let us show you the ways you can make your home feel bigger and brighter. Plus, glass room extensions are great for creating a greater connection to the outdoors.

Before you start

When designing this style of addition to your home, you need to take a few things into consideration.

First of all, decide what you actually want to achieve. Do you want indoor-outdoor living? Or are you simply about bringing in more light? This will help you find which style of glazing is right for you.

One of the most important steps is finding out whether you need planning permission for your glass box extension. This is the process where you ask your local planning authority if you can begin building work to your property. There are some home renovations classed as permitted development, which means that if your glass rear extension meets the strict criteria, you might not require planning permission. Always check with your local authority on what’s allowed and use the Planning Portal to do your research, too.

Another key consideration when building a glass rear extension is the temperature inside. Sunlight shining into your space is beautiful, but you don’t want to overheat in a big glass box. On the flip side, these spaces can also become a little too chilly in winter, which is why the construction needs to be well balanced.

This is where something called solar gain comes in – it’s the increase of temperature due to the natural heat from the sun. Your architect will take this into consideration when designing your space.

Of course, there’s also the issue of privacy. A lot of glazing means a lot of opportunities for neighbours to look in, so keep this in mind when drawing up the plans for your glass rear extension.

Glass rear extension styles:

Double-storey rear glass box extension

Double-height designs can transform a property, but must be well insulated and ventilated to manage heat rising. This property has been opened with a rear glass box extension to create an ultra modern, light-filled home.

A two-storey glass rear extension
This project by Architecture for London cost around £660,000. Structural engineers: Cambridge Architectural Research. Photography: Christian Braile.


Once a spot to house fruit trees in winter, today’s orangeries are an extension of the home and even suitable for important rooms such as open-plan kitchens. The distinct difference between these and conservatories is that orangeries have a solid flat roof with at least one roof lantern.

A large open-plan space in a conservatory with a generous rooflight
Designs from Hampton Conservatories start from £60,000.

Extension paired with a picture window

Incorporating a window seat into a rear glass extension can really help to strengthen the connection to the outside, rather than feeling as though you are taking away precious garden space. Plus, the glass roof will really brighten up the room. Combining glazing with the warmth of natural wood further enhances the link.

An extension with a picture window also allows you to add a comfortable seat
This extension project by Amos Goldreich Architecture cost around £300,000. Photography: Ollie Hammick.

Rear glass extension

All too often, rear extensions leave the middle of the house feeling dark and restricted – particularly if you already have low ceilings. Glass helps to overcome this, bringing in more natural light. Davide di Martino, director at urban architecture firm Unagru, designed this contemporary frameless glass box to achieve maximum brightness.

A fully glazed rear glass extension lets in plenty of sunlight
This project by Unagru cost around £70,000. Photography: Attilio Fiumarella.

Glass rear and side-return extension

Create a glazed courtyard in a disused side-return by extending out to the party wall – but make sure you can get agreement from your neighbours first. Here, with a budget of around £400,000, architect Emil Neumann at Paul Archer Design used glazing to expand the existing living space into an open-plan area. Thanks to fully retractable glass doors, it enjoys uninterrupted views to the garden. 

A rear and side return extension can let plenty of light into your home
Project by Paul Archer Design.

Indoor-outdoor-friendly rear extension

The rise in open-plan living has led to an increased interest for glass extensions, because glazing running across the different zones can help achieve a seamless flow. Indoors, the owners chose Arena Grey porcelain tiles, £96 per sq m. Outside, the flooring is in Cortina stone, £90 per sq m. Both are from Stone & Ceramic Warehouse.

To create an almost seamless indoor-outdoor space, add large sliding doors

Side-return extension with skylights

Skylights can have a huge impact on a side-return extension and make the most of unused space. Frameless glazing offers clear views and a contemporary aesthetic, though it can be costlier to purchase and install.

Side-return extension with skylights
A similar project by Yard Architects would cost around £200,000. Photography: Alexander James.

Need more help? How to choose glazing for your kitchen extension

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