What is Curtain Walling?

Introduction

What is Curtain Walling? Curtain walling is a non-structural outer covering of a building, usually consisting of glass and aluminium frames, that protects the building from the weather while not carrying any of the building’s weight. But what exactly is a curtain walling system, and why has it become such a staple for contemporary façades? In this post, we’ll explore the concept, components, benefits, and common applications of curtain walling, helping you understand how this architectural solution shapes the look and performance of today’s buildings.

Curtain walling explained

A curtain walling system is an exterior cladding that hangs like a curtain from the structural frame of a building, rather than bearing the structural loads of the building itself. This distinction means the curtain wall is primarily responsible for weather resistance, thermal performance, and aesthetics, while the structural system supports the building’s weight.

Curtain walling is typically composed of lightweight aluminium frames, glass panels, and sometimes composite panels or stone. The result is a sleek, continuous façade with minimal visual interruption and the flexibility to accommodate large glazed areas.

Key components of a curtain walling system

Below is a list of the different parts of a curtain wall to help understand how it works in practice:

• Subframe or mullions: Vertical members that transfer wind loads and provide attachment points for infill panels.
• Sashes or transoms: Horizontal members that complete the grid and support infill panels.
• Infills: Glass panes, insulated panels, or stone/slab elements that fill the spaces within the curtain wall.
• Mullion-to-floor connections: The interface where the curtain wall attaches to the main structural frame, designed to accommodate movement and weather sealing.
• Weather seals: Gaskets and seals that prevent air and water ingress while allowing for movement due to temperature changes and wind loads.
• Thermal breaks: Insulating barriers between the inside and outside curious of metal components to minimise thermal bridging.
• Spandrel panels: Often used to enclose non-vision areas of the façade, typically at floor levels where there is no need for transparent glass.

How curtain walling systems are configured

Curtain walling can be configured in several ways to suit different design intents and performance requirements:

• Unitized systems: Panels are manufactured and glazed as complete units in a factory
• Stick systems: On-site assembly of mullions, transoms, and infill panels
• Hybrid systems: A combination of unitized and stick elements
• Structural silicone glazing: A method where glass panels are bonded to the frame with structural silicone

What is the difference between structural glazing and curtain walling?

While curtain walling and structural glazing both share a common goal, bringing large spans of glass to the exterior of a building, they operate in different ways and are suited to different design ambitions, performance criteria, and budget considerations.

Curtain walling is a non-structural cladding system that hangs or attaches to the building’s structural frame. It normally consists of panes of glass held in aluminium or steel frames. It is non-load-bearing so the curtain wall transfers no significant structural loads to the building, instead its weight is supported by the building’s structure.

Structural glazing refers to a method where glass panels are bonded directly to the structural frame using structural sealants, typically without visible frames around the glazing. In this system, the glass itself becomes a primary load-bearing element for the façade, with the silicone or other advanced sealants forming a continuous, airtight, weatherproof bond between glass panes and the framework.  

Benefits of curtain walling

Curtain walling offers a range of advantages for modern buildings:

• Aesthetic Appeal: Large, seamless glazing provides abundant daylight and a contemporary, high-end look.
• Natural Light: Expansive glass areas reduce the need for artificial lighting during the day and enhance occupant well-being.
• Weather Resistance: Properly designed curtain wall systems keep rain, wind, and temperature fluctuations from penetrating the building envelope.
• Thermal Performance: With insulated glass units and thermal breaks, curtain walling can contribute to energy efficiency and thermal comfort.
• Acoustic Control: Double or triple-glazing options and careful detailing help reduce exterior noise intrusion.
• Flexible Architecture: The modular nature of curtain walling supports varied shapes, sizes, and alignment with the building’s grid.
• Maintenance Access: Modern curtain wall systems are designed to allow for easy cleaning and access for inspections.

Considerations in curtain wall design and installation

Successfully implementing a curtain walling system requires careful planning and coordination:

• Structural interface: Coordination with the building’s structural frame is essential to ensure safe attachment and movement accommodation.
• Waterproofing details: Effective joints, seals, and drainage paths prevent water ingress and moisture buildup.
• Thermal performance: Selecting appropriate glass types, coatings, and spacer bars reduces heat transfer and condensation risk.
• Glazing method: Choosing between unitized or stick glazing affects installation speed, costs, and on-site complexity.
• Maintenance strategy: Regular cleaning, inspection for seal degradation, and replacement of damaged infill panels extend façade life.
• Fire performance: Depending on the project, curtain walls may need fire-rated glass or insulation to meet safety regulations.

Typical applications for curtain walling

Curtain walling is versatile and commonly used in a variety of building types:

• Commercial Offices: To create bright, inviting interiors with expansive views.
• Airports and Transit hubs: Durable façades that withstand heavy use and environmental conditions.
• High-rise Towers: Lightweight yet strong façades that minimize wind pressure effects and shading.
• Schools and Colleges: Modern aesthetics paired with robust performance.
• Healthcare Facilities: Cleanable surfaces and controlled environments, with careful glazing choices.

Maintenance and lifecycle considerations

A well-designed curtain walling system reduces life-cycle costs if properly maintained:

• Regular Inspections: Check seals, gaskets, and drainage paths for wear or blockages.
• Cleaning Protocols: Use suitable cleaning agents to protect coatings and prevent streaking.
• Seal Replacement: Over time, weather seals may degrade and require replacement to maintain performance.
• Glass Replacement: Damaged panes can be replaced with minimal disruption if the system is correctly designed.

What happens if one pane of curtain walling breaks?

If one pane of curtain walling breaks, only that individual glass unit is usually affected, and it can be replaced without altering the rest of the façade.

Here’s what typically happens:

• Safety glass behaviour:
  Most curtain wall systems use toughened (breaks into small blunt pieces) or laminated (cracks but stays held together by its interlayer) safety glass.

• Building remains weather-secure:
  Laminated inner panes or backup seals usually maintain some level of protection until repairs are done.

• Replacement procedure:
  A glazing contractor removes the damaged unit from the frame and installs a new one — usually from the outside using access equipment.

• Minimal structural impact:
  Because curtain walling is non-load-bearing, a broken pane does not affect the building’s structural stability.

Conclusion

Curtain walling represents a significant evolution in building envelopes, combining sleek aesthetics with practical performance. Its lightweight, modular nature allows for expansive, daylight-filled interiors while delivering weather resistance and energy efficiency when correctly specified. Curtain walling offers a versatile solution that can be tailored to your project’s climate, budget, and architectural goals. 

Aaran Glass offers free estimates for any curtain walling glass replacements. We offer a complete glass replacement package including; site surveys, risk assessments, mewps and a reliable and trusted service, contact us today.