Curtain Wall
A lightweight exterior wall that hangs from the structure and carries no building load.
Quick Answer
A curtain wall is a non-load-bearing exterior wall system, typically aluminum framing infilled with glass or panels, attached to a building's structure. It carries only its own weight and wind loads, transferring them to the floor slabs or frame. It keeps weather out while admitting daylight, and is common on mid- and high-rise buildings.
The Full Picture
A curtain wall hangs on the outside of the structure like a skin. Unlike a bearing wall, it does not support floors or roof; it carries its own weight and resists wind and seismic movement, passing those loads to the building frame through anchors at the floor edges. This independence lets designers use light framing and large areas of glass.
Two main approaches are used. Stick-built systems are assembled piece by piece on site, with mullions installed first and glass or panels placed afterward. Unitized systems are built in a factory as large panels, shipped to the site, and hung from the structure, which speeds installation and allows tighter factory quality control but needs more coordination and early procurement.
Performance is demanding. A curtain wall must resist wind pressure, manage building movement, limit air and water leakage, control heat transfer, and meet fire and smoke requirements, including firestopping at the gap between the wall and the floor slab. Performance is commonly verified with laboratory testing of mockups under standardized test methods.
For contractors, curtain wall is high-value and high-risk scope. It usually involves long lead times, specialty subcontractors, and complex interfaces with the structure, roofing, and waterproofing. Scope gaps, such as who supplies anchors, sealants, or slab-edge firestopping, are a frequent cause of cost and schedule surprises.
Real Examples
Common Misconceptions
People assume: A curtain wall is a structural wall.
Actually: It is non-load-bearing. It supports only itself and resists wind, passing those loads to the building structure through anchors.
People assume: Curtain wall and storefront are the same system.
Actually: Storefront is a lighter, typically single-story framing system, while curtain wall is designed to span multiple stories and accommodate greater movement and loads.
Frequently Asked Questions
What is the difference between curtain wall and storefront?
Curtain wall spans multiple floors and is designed for larger loads and building movement. Storefront is a lighter system generally used at ground level and one story at a time.
What are the main types of curtain wall?
Stick-built, assembled in the field piece by piece, and unitized, factory-assembled in panels. Some projects also use hybrid or spandrel panel variations.
Does a curtain wall carry structural loads?
Only its own weight and wind or seismic forces. It does not support the building's floors or roof.
Why is curtain wall considered high risk?
It has long lead times, complex interfaces with other trades, and demanding performance requirements for water, air, and thermal control, so mistakes are costly to correct.
How is curtain wall performance tested?
Typically through mockup testing for air infiltration, water penetration, and structural performance using standardized test methods published by organizations such as ASTM and AAMA.