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Glass extension for Victorian house

Glass Extensions: Designing Your Dream Home

25 October 2023
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Glass Extensions: Your Glazing Options Explained

When it comes to expanding and enhancing your living space, glass extensions offer a brilliant solution to merge your indoor and outdoor spaces. But are bifolds best for you, or will sliding doors suit? Rooflights or a complete glass roof? Or what about a simple over-sized fixed window to create a glass wall?

The ODC team delves into the various glazing options for glass extensions and glass structures with reference to some of their recent projects for inspiration.

Glass extension opens up mid-century home

 A mid-century home transformed by a glass extension featuring sliding doors and bespoke rooflight

Design Considerations for a Glass Room Extension

The purpose and use of your extension, its relationship to the main house and how you want to connect it to your garden will influence your choice of glazing. A quiet study or nook may only need bespoke windows and a carefully placed rooflight, whereas a busy family kitchen-dining area will need bifolds or sliding doors for easy access to a patio, and larger glass roof sections to ensure light reaches the furthest corners of a large open plan area.

When Bifold Doors are best for Glass Extensions

Aluminium glass extension with bifolding doors and rooflights in Chiswick

Bifold doors for a small terrace extension fold back from a centre point for maximum opening to the outside

If you want the option to open up the entire garden-facing wall of your extension, then bifold doors are a fantastic choice. They are customised to fit the exact dimensions of the extension, offering a seamless, sleek appearance when closed and of course, can be opened panel at a time depending on the weather. They are often specified with traffic doors for quick access in and out, without engaging the folding mechanism.

Permitted development allows changes to doors and windows, including the installation of sliding and bifold doors; we do advise an early consultation about Building Regulations approval and local authority permitted development.

Flats, apartments, maisonettes and, of course, listed buildings, all need planning permission for sliding doors. We have years of experience working with past clients on these types of projects, and while we can’t arrange for your planning permission, we can offer advice and solutions to help with the success of your application.

Bifolds have large glass panels, with up to 12 in a single bifolding system, giving you lots of natural light for your space, and crucially making it feel more spacious and inviting.

The panels run on a single track with a flush threshold to minimise the transition to your outside patio.

Bifolds are extremely versatile in design; they can fold to left or right, inwards, or out to the garden, or split from the middle.

You do need to consider the folded dimensions of the doors, either on the outside of the extension, or folding into the interior. The wider the system, the more panels, the more room you’ll need. This is exactly the kind of design detail and calculation architectural glazing designers offer.

Sliding Doors for Glass Extensions

Sliding doors for glass extension to London terrace

Glass extension with sliding doors transforms life for owners of a London terraced home

Sliding doors are a great alternative to bifold doors when space is an issue. They don’t require the same amount of clearance to fold out and work well in smaller side extensions.

If light and views to the outside are your priority, then aluminium sliding doors with slimline frames to maximise the glass surface area are an excellent choice. A one sliding/one fixed system will offer a transformative amount of light and a sense of the outside to the smallest space.

If on the other hand you want an ambitious wall of glass to sweep on all three sides of a large glass extension, sliding systems and fixed panels will achieve this in spectacular fashion.

Rear extension with sliding doors

When space has no limits: garage conversion and rear extension with walls of glass

Sliding systems can be designed to exceptional heights, so though your glass extension may have width restrictions, you can create a sense of soaring light and exciting architectural impact with doors up to six metres high!

Rooflights or a glass roof ?

SL800 slimline aluminium sliding doors, fixed windows and rooflights for extension in London

 A single storey extension for Georgian home lit by custom-made rooflights

We see architects incorporating both rooflights and glass roofs for extensions – both create extremely successful spaces.

Rooflights are an excellent choice for side extensions where wall space or privacy issues might prevent the installation of a window. They allow natural light to filter in from above. They’re perfect for extensions built up to property boundaries where a window overlooking a neighbouring property wouldn’t pass planning regulations. Customised frameless rooflights come in spectacular sizes and can create a stunning focal point in your extension.

Glass roofs deliver more of an atrium feel and year-round feel-good factor. Modular glass sections can include opening rooflights and feature solar control and self-cleaning films to make life more comfortable. For extensions that not over-looked, they can offer an exciting and contemporary glazing solution.

The simplest glazing solution of all: the bespoke fixed window

Glass extension with fixed window

A very popular side extension with glass roof sections, large picture window and delightful window seat

Fixed windows, though they don’t open, are perfect for side extensions where the primary focus is to bring in more light and to frame a favourite view. Strategically placed and with dimensions way beyond a conventional off-the-shelf window, a bespoke fixed window can turn your glazed extension into an architectural gem.

Glass Extensions for Period Homes? Absolutely!

Glass extension for village home

A dark period cottage on a windy Cotswolds hillside: a robust glass box extension with bifolds is the solution


Architects are frequently asked to expand period homes with a glass extension which blends modern design and open plan living with the original character.

Our design team have enjoyed designing glazing for all types of period home from Victorian semis, Georgian townhouses to thatched country cottages and think glass extensions for period homes are particularly successful for several reasons:

1. Maximise limited space
Period homes are often semi-detached, with relatively narrow plots and limited space for expansion. Glass side extensions make efficient use of this limited space by extending outward without consuming valuable garden or patio area.

2. Shed light on those period features
One of the defining features of period homes is their architectural character and detailing. Glass side extensions highlight these elements by bringing more natural light into the interior. They can also offer new perspectives on the original architecture, creating a stunning contrast between old and new.

3. Blend old and new 
Period homes often have distinct exterior features like bay windows, brickwork, or decorative facades that contribute to their visual appeal. Glass extensions offer an unobtrusive addition that respects the original architecture. Doors, windows, fixed glazed panels can all be customised to align with the proportions and architectural style of the period home. With over 200 RAL colours to choose from, frames can be finished in a colour to work with the original house fenestration.

4. Enjoy more garden views
Period homes often have delightful mature gardens. A glass extensions allow homeowners to maintain a visual connection with these outdoor areas. The large windows and doors create a sense of bringing the garden inside, enhancing the living experience and connecting residents with the natural surroundings.

6. Add versatile modern space
While period homes offer timeless charm, they sometimes lack the spacious, open-plan living spaces that modern homeowners desire. Glass extensions provide the versatility to create contemporary living areas that cater to today’s lifestyles. These spaces can be used for kitchens, dining rooms, family rooms, or even home offices, offering a modern twist to the classic charm of period properties.

Even if you have just engaged an architect, it’s never too early to get our design team involved! They’ll offer glazing solutions for extensions to complement a wide range of designs and budgets.

Find out more about ODC modular glass extension design featuring fixed glass panels, glass roofs or rooflights and sliding or bifold door systems