The Walled Garden

A frameless structural glass roof floods this garden extension with light

This Grade II listed Oxfordshire countryside home combined the original yellow brick of the boundary wall with bespoke frameless structural glazing to create a modern, light-filled side extension. The new living space overlooks the gardens and has been designed to house an open plan dining area and comfortable seating space.

The detached house is listed and located within the Cotswolds Area of Outstanding Natural beauty (AONB). This means that the house falls under strict planning requirements that IQ and the architect had to work to achieve. 

An impressive 52 metre squared of structural glazing was used to create the large frameless glass roof, made up of five 10m long panes joined together with slim black silicone joints and supported with frameless glass beams.

Structural glass beams were chosen to support the glazed roof in order to maintain the overall frameless design. They are made up of several layers of structural glass which is then laminated together to create a strong supporting beam. The glass used was further specified as low iron, in order to avoid the green tint that becomes more pronounced in thicker glass units like these ones.


When installing a glass roof, it is important to consider the direction that water will drain away to. This can be done in several ways, including installing a structural gutter to the join between the glass and the vertical supporting wall. For this project, the glass roof was designed to sit over the top of the supporting rear wall, at a slight pitch to allow rainwater to drain in that direction, away from the glass walls and casement doors.



Heat soak testing was conducted for each of the large glass panels before installation, a process which dramatically decreases the risk of the glass spontaneously shattering post-install, due to nickel sulphide inclusions. This precautionary treatment is recommended for projects with glazing that cannot be easily accessed to be replaced, as was the case with this glass roof - due to the large size and heavy weight of the glass panels, a crane was required to complete the installation.

A solar control coating was then applied to the heat tested glass, in order to help control the internal temperature of the extension. With such a large surface area of glass across the roof and two walls, sunlight is able to warm the space throughout much of the day, making it important to prevent too much solar gain occurring through the glazing.