architecture term
A curtain wall is a non-load-bearing exterior wall system; learn what is a curtain wall in architecture through mullions, spandrel panels, anchors, and frame logic.
orientation
What is a curtain wall in architecture? A curtain wall is a non-load-bearing exterior wall system, often glass and metal, that hangs from or is attached to a building frame. It keeps out weather and shapes the facade, but the main gravity and lateral loads are carried by the structure behind it.
Read a curtain wall through the frame, mullions, transoms, glazing, anchors, joints, and spandrel panels. Mullions are the vertical members that divide the facade; transoms are horizontal members; spandrel areas hide floor edges or opaque backing between vision glass. These parts make the system readable as construction, not only as a smooth glass image.
| Part | What it does | How to recognize it |
|---|---|---|
| mullions | Vertical members that divide glass or panel fields and help make the envelope readable from outside. | Look for repeated upright lines between panels, especially where the facade forms a grid or diagonal pattern. |
| transoms | Horizontal members that tie the panel system together and often align with floor or window divisions. | Follow the cross pieces that separate stacked glass zones or mark the rhythm between floors. |
| vision glass | Transparent glass areas admit light and view while helping the exterior read as an occupied building. | Find the panels you can see through, then separate them from darker or opaque floor-covering zones. |
| spandrel panels | Opaque or treated zones that hide floor edges, structure, insulation, or backpan behind the exterior face. | Look for darker, patterned, or solid panels between rows of transparent vision glass. |
| anchors | Connections transfer the curtain wall's weight and wind loads back to the main structural frame. | They are often hidden, so infer them where a continuous skin passes floor edges without becoming the floor frame. |
A curtain wall usually sits outside the floor edges as a continuous skin, while a window wall often fits between floor slabs. The distinction matters because it changes drainage, attachment, fire-stopping, facade depth, and the rhythm a viewer sees from outside. In plain terms, the curtain wall is hung from the frame; it is not the frame itself.
| Part | What it does | How to recognize it |
|---|---|---|
| Curtain wall | A continuous non-load-bearing envelope attached to the building frame. | Look for a skin that passes floor edges and reads as one exterior system rather than separate window openings. |
| Window wall | A wall or window system that usually fits between floor slabs rather than hanging past them. | Look for slab edges or floor-by-floor breaks that interrupt the exterior surface. |
| Structural frame | The beams, columns, core, or diagrid that carries main loads behind or alongside the envelope. | Find the heavier system that explains gravity, lateral resistance, and the building's real support. |
30 St Mary Axe is the clearest atlas next step because its glass facade, diagonal structure, rounded profile, and repeated panels make the skin easy to inspect. The tower is not useful only as a nickname or skyline object. It helps readers ask how a glass envelope, structural pattern, and office-floor logic produce one recognizable form.
Use it for glass envelope, repeated panels, diagonal structure, and a recognizable tower profile.
Use it for the wider vocabulary of exposed systems, technical expression, and engineered envelope logic.
Use it to compare transparent, reflective, and skin-led buildings without treating every glass facade as the same system.
Use this visual glossary when studying modern towers: vision glass is the transparent field; spandrel glass or panels cover floor zones; mullions and transoms organize the grid; gaskets and joints manage movement and water; anchors connect the assembly back to the building frame. The value is in seeing which part is surface, which part is structure, and which part is weather control.
Not every glass building is best explained by the curtain wall label. Some facades use load-bearing walls, structural glass, double skins, screens, or heavy frames that change the reading. The safer test is whether the exterior wall is a non-load-bearing envelope attached to a separate frame and whether its parts can be named on the building.
The strongest curtain wall clue is separation between skin and structure. If the outer wall mainly encloses, drains, admits light, and shapes image while another frame carries the building, the term is probably useful. Carry that test into 30 St Mary Axe and other glass-building pages before comparing style or skyline effect.
Best next page for checking whether glass skin, structural pattern, and office-floor logic align.
Best next page when the question is broader than a non-load-bearing glass envelope.
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References used for facts, location data, image credits, and architectural context on this page.