At a system level, the distinction between curtain walling and structural glazing is often overstated. Structural glazing is not a separate façade category so much as a method of fixing glass within a curtain wall system. That distinction has practical implications for procurement, sequencing, and long-term risk.
A curtain wall is, fundamentally, a non-load-bearing external envelope supported by the primary structure. It transfers its own dead load and environmental loads, principally wind, back to the building frame via brackets and anchors. In most UK projects, this is achieved using aluminium-framed systems, either assembled in situ (“stick”) or installed as pre-fabricated panels (“unitised”).
Structural glazing, by contrast, describes how the glass is retained within that system. Instead of being mechanically clamped with pressure plates and caps, the glass is bonded to the frame using structural silicone, allowing the external face to appear flush. Crucially, this means that structural glazing curtain wall systems are still curtain walling. The distinction lies in the interface between glass and frame, not in the overall façade classification.
So, what is the difference between a curtain wall and structural glazing?
The biggest difference lies in how loads are transferred from the glass to the frame. In a capped curtain wall system, wind loads acting on the glass are transferred through mechanical fixings (pressure plates and gaskets) into mullions and transoms. The load path is explicit and inspectable. Replacement is also relatively straightforward: individual panes can be removed externally without disturbing adjacent units.
In structurally glazed systems, the load path is mediated through structural silicone bonds, which must resist shear and tensile forces over time. These bonds are designed to accommodate movement from thermal expansion, building sway, and differential deflection between floors. However, the performance of the bond depends on strictly controlled factory conditions, including surface preparation, curing time, and environmental controls. This is one reason why true structural glazing is rarely executed on site.
A commonly overlooked nuance is the distinction between structural glazing and silicone glazing. Many UK systems described as “structurally glazed” are in fact silicone weather-sealed systems, where the glass is still mechanically retained but the external caps are replaced with silicone joints for aesthetic purposes. In these cases, the performance characteristics, such as air tightness, water resistance, and structural behaviour, are largely unchanged; the difference is visual rather than functional.
True structural glazing introduces supply chain limitations that do not apply to conventional curtain walling. Because the integrity of the façade depends on bonded interfaces, fabrication is typically centralised in specialist facilities. The brief notes that fully structurally glazed curtain wall systems are largely supplied from continental Europe, with limited UK-based capability.
This has two operational consequences:
By contrast, stick systems allow a degree of site adjustment, albeit at the cost of programme duration and installation consistency.
From a regulatory perspective, both systems must satisfy the same core requirements under UK Building Regulations, including Part L (thermal performance) and Part B (fire safety). However, the route to compliance differs subtly.
In structurally glazed façades, the absence of external caps reduces thermal bridging at the pressure plate interface, but this benefit is often marginal compared to the overall façade U-value. More significant is the challenge of demonstrating the durability and long-term performance of the silicone bond, which relies on testing regimes and manufacturer warranties rather than purely mechanical verification.
Fire performance introduces further complexity. While the glass itself may be rated, the behaviour of bonded systems under fire conditions, particularly the integrity of sealants and interlayers, requires careful assessment. Under the Building Safety Act 2022, this shifts greater emphasis onto documented testing, traceability, and design responsibility.
The choice between systems affects sequencing in ways that are not always immediately visible at tender stage. Unitised structural glazing allows for rapid enclosure of the building envelope, often floor-by-floor, which can accelerate internal trades. However, this depends on early design freeze and precise coordination with structural tolerances. Misalignment between the primary frame and façade panels can lead to rework or, in extreme cases, panel rejection. Stick systems, while slower, can absorb greater dimensional variability. This can be advantageous on projects where structural tolerances are uncertain or where design development continues into the construction phase.
Replacement strategy is one of the more consequential differences. In capped systems, failed units can typically be replaced individually with minimal disruption. In structurally glazed systems, replacement may require de-bonding and re-bonding processes, often necessitating specialist access and extended downtime. This has implications not only for maintenance cost but also for risk allocation in contracts, particularly where façade performance is tied to long-term warranties.
Projects such as high-profile towers have demonstrated the visual appeal of fully flush façades. However, the operational consequences, including restricted supply chain, higher fabrication precision, and more complex maintenance, mean that the decision is rarely aesthetic alone. For quantity surveyors and project teams, the key question is not which system is “better”, but which aligns with the project’s risk profile, programme constraints, and procurement strategy. In many cases, the perceived distinction between curtain walling and structural glazing collapses into a more practical consideration: how the façade is assembled, and where the associated risks are carried.
Every project responds differently to cost pressures, programme constraints, and regulatory requirements. Seeing how these factors are resolved on real schemes can be more useful than theory alone. Explore our recent façade and glazing projects here.