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    A guide to
    glass box extensions

    arrow Back to blog 22nd September 2017

    Glass box extensions are seen by many as a futuristic, state-of-the-art addition to the home, cleverly introducing abundant natural daylight from all angles.

    These frameless glass boxes can be used as a genuine structure – like a conservatory or extension – affording panoramic external views that connects a property’s interior so well with its surroundings.


    This can be achieved with the use of supporting aluminium sections, which are designed with a profile that’s as slim as possible in order to minimise sight lines and ensure maximum light transmittance for interiors. Just by using structural glass together you can extend a home’s floor space whilst flooding the rest of the property with abundant daylight.


    You would be forgiven for thinking that glass is used solely in windows, rooflights and doors, but the strength of aluminium enables it to hold larger, thinner panes of glass; opening up an entire face of a property to its outside areas.

    Glass boxes and energy performance

    glass box extension offers excellent energy performance, with low-e coatings and argon gas fillings capable of ensuring high levels of insulation within the framework of any new glass structure. Combine this with the highly effective glass treatments and coatings such as heat-reflective specifications – which we’ll talk about in greater depth later on – and you’ll ensure a glass box that’s never a heat loss concern in the winter or, at the other end of the spectrum, a solar gain concern in the summer.

    A unique architectural statement

    The design and build of a clear, frameless glass box house extension is guaranteed to add light and style that’s bespoke to your property. If you’re looking to invest in an extension that not only incorporates within the architectural design of the rest of your home but acts as a translucent bridge between your interiors and the outside, a custom-built glass box is a very sensible choice. The structurally strong glazing will last for many years, with no need for periodic repairs or upgrades.

    Planning permission for glass box extensions

    Properties situated within conservation areas or those that are listed will always require planning permission for this kind of extension. There is a need to prove that the new work will be in-keeping with the period aesthetics of the original building. However, most small glass box extensions on other homes tend to be covered by the government’s Permitted Development Rights. As ever, if you have any doubts as to whether you need to seek planning permission, it is always best to contact your local planning authority for clarification.

    Multiple functionality options

    It’s virtually impossible to rival the ‘wow factor’ of a fully glazed box extension. Its design flexibility is truly one of its biggest assets. Whether it’s a standard single-storey rear extension to your living space or a design that connects multiple solid parts of your home, or even provides access to your roof, the functionality options are endless. Your glass box extension can even be designed with openings. Sliding doors within your glass box can provide access to terraces and patios and much-needed ventilation to your living space.

    Glazing specifications for glass structures

    Glass box extensions can be tailor-made to precisely how you want to live. If you’re planning on spending lots of time in your new space, it might be a good idea to consider solar control coating, which reflects the vast majority of the sun’s UV rays, preventing living areas from becoming too hot and uncomfortable whilst still enjoying the abundant natural light from all angles. By the very nature of having a glass box structure attached to your home, it’s not difficult for others to see into your stunning new space. However, if that’s a genuine concern, it is easily remedied by applying an obscure glass treatment to create that all-important privacy.

    Connecting life on more than one level

    Overcoming design challenges is something we relish at Sunsquare, providing stunning bespoke features with timeless aesthetics. That was certainly the case with our project at Rose Valley, for which we were specified by Spatial Design Architects, who specialise in contemporary, sustainable and hybrid architecture for new-build and existing buildings.

    Aside from the need for our fixed SkyView rooflights for the property’s new flat roof rear extension, the home required a link between the living areas on the first floor and those on the ground floor – without extending the single storey rear extension into two storeys. We subsequently designed, manufactured and installed a glass box extension for the first floor, which would filter light down into the ground floor living space and make the first floor environment more appealing in the process.

    With rock-solid energy performance and structural integrity, our glass box extensions can provide the perfect architectural statement, but not at the cost of your privacy.

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