Structural Glazing for House Extensions

Specifying Fluid Glass

This blog post explores the role of structural glazing in house extensions, highlighting its benefits, key considerations, and the latest technical details available through the Detail Library.

The latest set of structural glazing details have been created in collaboration with Fluid Glass, who are specialists in innovative glazing solutions. They supply high-quality systems for a wide range of applications and are experts in the installation of structural and architectural glazing.

What Is Structural Glazing?

Structural glazing is a broad term that refers to frameless glazing – in which the glass itself bears part of the structural load. As structural glazing is exceptionally strong, it doesn’t require bulky frames for support like traditional glazing systems. The glazing consists of reinforced, load-bearing glass panels typically bonded with a high-strength silicone adhesive. This opens up a wide range of design possibilities – including the use of impressively large fixed glass panels. The absence of visible framing results in a minimal, clean aesthetic often seen in contemporary design.

Why Choose Structural Glazing for a House Extension?

There are several reasons why structural glazing can be a great addition to extension projects:

• Increased natural light: Large expanses of glass allow daylight to penetrate deep into the interior, improving ambience and reducing the need for artificial lighting.

• Connect to the outdoors: Glazing that stretches from floor to ceiling or wall to wall helps dissolve the boundary between house and garden.

• Contemporary appearance: The lack of visible frames and the use of slimline profiles support a modern, clean look.

• Uninterrupted views: With no mullions or bulky sections, structural glazing provides clear sightlines to the outside.

• Improved spatial quality: By creating open, light-filled spaces, structural glazing can enhance the perception of space within a home.

This type of glazing is particularly suited to creating uninterrupted views, maximising natural light, and delivering a seamless connection between internal and external spaces.

Common Applications in Extensions

Fluid Glass’s product range includes a number of systems well-suited to domestic extensions, such as:

• Sliding doors: Ideal for garden-facing elevations, these doors combine large openings with smooth operation and minimal thresholds.
• Fixed windows: Often used on side returns or rear extensions to provide light without compromising privacy or wall space
• Glass roofs and skylights: Particularly beneficial in lean-to extensions or infill schemes where natural light may otherwise be limited
• Corner glazing: A striking way to articulate building edges, often used to create a sense of openness
• Glass links: Used to connect existing structures, these offer a light, transparent transition between spaces

Featured Products in the Detail Library

This month, a selection of Fluid Glass glazing system details have been added to the Detail Library, including details for:

• Structural glazed walls and windows
• Side return skylights
• Lean-to glass roofs
• Aluminium sliding doors

All of these systems have been chosen with house extensions in mind, providing both design inspiration and technical guidance for architects and designers. They have been created in close collaboration with Fluid Glass to ensure coordination between the various building elements. These details demonstrate how carefully considered installation methods can enhance the overall performance of the system in terms of energy efficiency, moisture resistance, and structural integrity.

Design Considerations

While structural glazing can greatly enhance an extension project, it’s important to address several technical and regulatory factors:

• Size limits: The size of glazed units may be constrained by production and handling logistics. Access to the site (whether there is access down the side of the house for example) should be considered to ensure that any large panes of glazing can be moved into place safely and without putting construction workers at risk
• Thermal performance: New glazing must meet U-value targets under Part L of the Building Regulations. The amount of new glazing will determine whether SAP calculations are required to show that the project will meet the thermal performance requirements. If the area of new glazing is above the guidance outlined in Part L then calculations will be required.
• Orientation and overheating: Whilst Part O does not apply to house extensions, the risk of overheating should still be considered. South-facing glass may require shading or solar control coatings to ensure a comfortable internal environment. 
• Reveal depths: The position of the glazing within the reveal will impact the appearance both internally and externally. It will also affect the thermal performance of the junction. Keep reading for a case study on this aspect of the design.
• Wind and weather resistance: Glazing systems must be able to withstand external forces, including wind pressure and weather conditions. 
• Privacy and blinds: Particularly important for urban sites or where neighbouring properties are close by.
• Security: Depending on the position of the glazing, it is likely that products will need to meet Part Q requirements, with appropriate locks and safety measures.
• Accessibility:  Depending on the position of the glazing and any project specific requirements, it is likely that products will need to meet Part M requirements, with step-free access and be easy to operate.
• Fire performance: Glass in certain locations (such as close to a neighbouring property or ownership boundary) must meet more stringent fire safety standards. Refer to Approved Document Parts B for the requirements. 
• Acoustic performance In urban environments, noise reduction can be a significant concern. Structural glazing systems should be designed to minimize sound transmission between interior and exterior spaces, helping to create quieter, more comfortable living and working environments.
• Cleaning and maintenance: Consideration must be given to cleaning access, and long-term upkeep.
• Strength: Part K provides guidance on safety glazing. This approved document requires the use of toughened or laminated glass in certain locations, such as low-level windows or glass used in balustrades.
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An experienced supplier such as Fluid Glass is well versed with the technical requirements listed above and has various solutions to ensure that their structural glazing system can meet or exceed them. Early engagement with Fluid Glass and a discussion of project specific requirements will allow them to provide initial design advice and help with project planning.

Detail Study: Integrating Fluid Glass Structural Glazing in Extension Walls

Here we take a closer look at one of the details created by The Detail Library in collaboration with Fluid Glass. Detail EW05 shows how structural glazing can be integrated into a masonry wall – and in particular the resolution of the jamb detail.

EW05 shows Fluid Glass structural glazing in an extension masonry cavity wall. It includes 4 different jamb detail options for the positioning of fixed structural glazing within a masonry cavity wall.

These options are:

• a half brick return with the glazing fixed back to steel structure
• a half brick return with the glazing fixed back to a blockwork return
• no brick return with the glazing fixed back to the brickwork outer leaf
• a full brick return with the glazing fixed back to the blockwork inner leaf

These are some of the key considerations for the jamb details generally:

• Thermal performance: Each installation option emphasizes the importance of minimizing cold bridging, which is vital for improving thermal efficiency and reducing energy costs
• Moisture and weather resistance: The inclusion of edge insulation and the eDPM ensures that the system is protected against moisture ingress, which could otherwise affect both the structural glazing and surrounding wall materials
• Structural integrity: The use of steel structure or blockwork returns are provided where required to ensure a robust fixing of the glazing to the wall. 

Each of the jamb detail variations change the appearance of the glazing and the thermal performance of the junction. The diagrams below highlight the features that have been incorporated to enhance the performance of each junction.

No Brick Return

The no brick return option places the frame away from the insulation zone, on the cold leaf of the external wall. Therefore the junction would not perform as well thermally as the other options.

To improve the performance of the junction, the internal insulated plasterboard finish should be returned into the window.

Each variation of the detail reflects a considered approach to performance supporting the architectural intent. 

Detail EW05 also shows two section options, demonstrating different base level finishes, different lintel and support options, window position and varying visibility of the frame. The full details (including DWG, SKP & Revit formats) are available to download here. We’re excited to have Fluid Glass’s products featured in The Detail Library. 

Other Fluid Glass details available in this set are:

• EW06 Structural Glazing Box Window in Extension Wall
• EW07 Structural Glazing Skylight in Extension Parapet
• EW08 Structural Glazing Skylight in Extension Side Return
• EW09 Structural Glazing Skylight to Side Return New Extension Walls
• EW11 Triple Sliding Door in Extension Wall

Resources

Download the Details

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