Glass box extensions are widely seen as the 21st century reinvention of the classic conservatory. They are equally successful as a striking external detail on a house as they are at maximising space internally. Paired with the minimal sightlines of Minima’s slimline sliding doors, these elegant extensions result in seamless division between the inside and outside.

Ultraline 4 panel sliding doors with glass to glass corners installation Watford


What is a glass box extension?

The terms ‘glass extension’ and ‘glass box extension’ are used interchangeably by designers to refer to an addition which is predominantly glazed. Most often these are at the rear of a property. As family life increasingly pivots around the kitchen living room, it’s here that the majority of glass box extensions are created.

Advancements in architectural glazing and their structural capabilities have seen increasingly innovative ways of using glass to add striking design-led additions to homes both old and new. Where once the sunroom and conservatory—or their grander cousins, the orangery—were the height of fashion, this has given way to more contemporary designs made up of frameless glass.

Why are glass boxes popular?

Rooms made entirely of glass can be installed as a way of creating a constant visual connection to the garden, unobstructed by solid walls and roofs. The resulting space makes the most of the sunlight regardless of the time of year. Glazing plays tricks with the eyes, too. A glass box extension complemented by minimal frame glass sliding doors not only has the effect of bringing the outside in but can also make a relatively small space feel considerably larger.

Arthur Road Ultraline Sliding doors glass box extension minima sliding doors installation


Which properties do they suit?

Almost all, in short. As many owners of classic Victorian and Edwardian terraced houses have discovered, opening up the back of the property with glass sliding doors, rooflights or a glass box extension has a dramatic impact. Rooms that were once often starved of light are replaced with spaces that help to dissolve the boundary between the house and the garden. They open up the kitchen and dining area and introduce a generous source of natural light.

Another popular intervention in terraced houses is to extend into the so-called side return. Using outside space that is often redundant, this work transforms otherwise dark and narrow kitchens into light-filled open planning living spaces. The benefit of this approach is that it creates extra internal space without encroaching into what are often limited gardens.

Modern in form, glass box extensions are versatile in their applications in country houses, too. While many assume that they will jar with traditional or historic buildings, the reality is rather different. In most cases, glass box extensions can be added within permitted development rights, allowing owners to extend without securing planning permission, providing the extension is within certain size parameters. For listed properties, those in green belt areas, national parks or AONBs, restrictions are tighter. However, extensions made up of large areas of glazing with minimal sight lines are often (although not always) favoured by conservation and planning officers. The simplicity of the design doesn’t alter the character of the original building—they are regarded as lightweight additions.

Arthur Road Ultraline Sliding doors glass box extension minima sliding doors installation


Glass box extensions and sliding doors

Frameless glazed boxes provide wonderful internal spaces for dining or relaxing. Fitting an upholstered window seat into the reveal creates a perfect place sit down with a book or magazine. The concept pairs perfectly with sliding doors which introduce a physical connection to the garden. Our precision engineered glass sliding doors have narrow 20mm frames all the way round. These allow designers and architects to design glass rooms with unique opening solutions without compromising the fully frameless aesthetic and transforming garden rooms into outdoor living rooms during the summer months.

Related read: Why use an architect when planning an extension

Are you thinking about a glass box extension? Contact us now to find out more about Minima Sliding award-winning, British-made sliding doors.