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6 Glass Box Extension Ideas

glass box extension to 17th century farmhouse
(Image credit: van Ellen and Sheryn)

Long gone are the days when a standard PVCu conservatory was the only way to introduce more light and space to a home.

Thanks to strides made in the structural glazing industry, walls and ceilings made of glass are now offering interesting solutions for extension projects. Here, we look at some fine examples.

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A Bold Box Extension

In order to create a spacious open plan family home, the old conservatory on the ground floor of this house in Notting Hill was knocked down and replaced with a glass box structure by Raven Glaze. A steel beam across the rear has allowed the space to be completely open to the rest of the ground floor — offering a through-view straight to the garden from the front door. The new glazed addition, complete with full-height glazing as well as a glass ceiling, allows the family to enjoy uninterrupted views of the garden.

glass box extension to replace dated conservatory

(Image credit: Alison Hammond)

A Minimalist Dining Space

This project from Jeff Kahane + Associates evolved from the homeowners’ desire to replace their semi-derelict conservatory with the most minimal new structure possible, creating a new dining area off the rear elevation of their Grade II-listed Georgian house. 

minimalist glass box extension

(Image credit: Jeff Kahane + Associates)

“This new frameless take on the modern conservatory, seated on a battered stone plinth and guarded by a glass balustrade, is designed so that 73% of its sides can be folded open on warm days. Glass specialists Trombe, working with us, developed a new 180° hinge to achieve this,” explains Jeff Kahane. 

A slender portal frame is braced back to the rear of the building by two beams, holding eight adjustable spotlights — solving the perennial problem of how to illuminate a fully glazed space. The beams and frame are clad in mirror-polished stainless steel that, in sunlight, further helps to minimise the impact of the new space. 

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A Feat of Engineering

While many glass box extensions are built solely on the ground floor, Giles Pike Architects has achieved an impressive feat of engineering by introducing a two-storey glass addition to a 19th-century five-storey home in Fulham.

glass box extension

(Image credit: Giles Pike Architects)

Designed to open up the living accommodation over several floors, the structural walls were removed and replaced with a network of steel beams and stub columns to support the new floor area at each level. Full-height glazing, sliding glass and a glass roof complete with minimal framing offer uninterrupted views of the garden while bringing in plenty of light. A sleek steel balcony and external open tread staircase also connects the upper living accommodation to the garden.  

A Frameless Addition

Peter and Alison Dudgeon’s desire to inject light into their period property led them to approach architects AR Design Studio — well known for their work with glass. Director of the practice, Andy Ramus, designed a contemporary frameless glass extension which would open on to the rear garden to provide a flexible inside/outside space. It is made from 12mm outer sheets of toughened glass and is supported by a structure of low-iron ‘white glass’ which does not give off the green tinge of thick glass, making it less prominent.

Contemporary kitchen-diner in glazed extension to a period home

(Image credit: Martin Gardner c/o AR Design Studio)

To prevent overheating in summer months, the glass is coated with solar-controlling titanium dioxide which reduces the amount of heat entering the building by 59 percent, while large glass doors provide natural ventilation.

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A Slice of Glass

Providing additional space to a basement flat in west London, this sleek glazed extension by Granit Architecture + Interiors offers the homeowners a new light-filled kitchen diner as part of a more extensive refurbishment project.

glass box extension to basement flat in west London

(Image credit: Andrew Beasley)

In order to improve the quality of living to suit a modern, busy family, the existing rear extension was demolished to create a new kitchen and dining space over an increased footprint, within a frameless glazed box to maximise on daylight and allow natural light to reach other spaces within the apartment. Sliding doors leading out to the patio also address the connection with the garden. The new addition appears as a sliver of glass against the new white rendered façade. However, due to its narrow form, it maintains the homeowners’ privacy from the flats above.

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A Glass Farmhouse Extension

Divided by a stone chimney stack to tie the extension in with the existing stone farmhouse, this glazed addition marries old with new. Designed by van Ellen + Sheryn Architects, the glass box extension houses a new open plan kitchen/living/dining space and, thanks to the full-height glazing, the homeowners now benefit from views out over the garden. Sliding glass doors and a level threshold also promote indoor/outdoor living.

glass box extension to 17th century farmhouse

(Image credit: van Ellen and Sheryn)

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