Curtain Wall vs Window Wall: Metalwork Differences Explained

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A curtain wall is a lightweight, non-structural cladding system hung from the building's frame, usually spanning several floors. A window wall is assembled floor by floor, typically sits between slab edges, and is simpler to install, which makes the choice mainly a question of height, structure and detailing.

What a Curtain Wall Is

A curtain wall is an outer skin of glass and metal framing that carries only its own weight and wind loads back to the primary structure. The framing usually consists of continuous vertical mullions and horizontal transoms, often in aluminum or steel, with glazing units set into the grid.

Because the system spans multiple floors, it is typically fabricated as large panels in the factory and lifted into place. Anchors connect the wall to slab edges, allowing controlled movement for thermal expansion and building drift.

What a Window Wall Is

A window wall is a storey-height glazed system installed between floor slabs, with each floor treated as its own assembly. The sill, head and jamb details are repeated at every level, and the wall is usually anchored to the slab edge at each floor.

This approach suits buildings where floor-to-floor separation is important for fire compartmentation and where installation can proceed one level at a time without large crane lifts.

Key Metalwork Differences

The main difference lies in how the metal frame is designed and connected. Curtain walls rely on long, continuous profiles that must handle deflection over several storeys, while window walls use shorter members with more frequent anchor points.

Curtain wall: continuous mullions, pressure-plate or structural-silicone glazing
Window wall: floor-height frames, repeated sill and head details
Curtain wall: greater attention to thermal movement across long spans
Window wall: simpler anchorage and more accessible replacement of individual units

Structural and Movement Considerations

Both systems must accommodate building movement, but the strategy differs. A curtain wall needs sliding or floating connections at every slab edge so that frame loads and movement are not transferred into the glass. Window walls can often use simpler fixings because movement is absorbed over a shorter height.

Wind pressure, seismic drift and the stiffness of the primary frame should be checked by the structural engineer before profile sizes are fixed. Exact design values belong in the engineer's calculations, not in general guidance.

Installation and Fabrication Factors

Curtain walls are usually prefabricated as unitised panels, which shortens site time but requires precise coordination of dimensions and lifting equipment. Window walls can be built more progressively, which gives flexibility when site conditions change or when floors are completed at different times.

Early coordination with the metalwork supplier on tolerances, interface details and sequencing avoids costly rework on site.

Choosing Between the Two

Consider the building height, the number of storeys the glazing should visually cross, the structural frame, fire separation requirements and the construction programme. Curtain walls suit continuous facades and dramatic elevations, while window walls suit repetitive floors and projects with tighter site access.

Discussing the envelope early with a metalwork fabricator helps check which system fits the design intent and budget logic before drawings are finalised.

Frequently asked questions

Is a curtain wall always more expensive than a window wall?

Not necessarily. Costs depend on height, unit size, glazing type, installation method and project scale, so each option should be evaluated against the specific design.

Can a window wall look like a continuous curtain wall?

Yes, with careful alignment of mullions, spandrel panels and floor lines, a window wall can achieve a similar visual appearance, though the joint pattern and structural behaviour will differ.

Which system is better for fire safety?

Both can meet fire requirements when the slab edge, spandrel and firestop details are designed correctly. The fire strategy should be confirmed with the fire engineer for each project.

Do you handle drawings and on-site measurement?

Yes, the process starts with an inquiry and photos, followed by on-site measurement, drawing and written specification, client approval, factory production, finishing and installation.

Common mistakes to avoid

Choosing a system before confirming the structural frame and movement joints is a common error. Designing the interface details late in the process often forces expensive changes to profiles and anchors.

Our recommendation

Involve the metalwork fabricator at concept stage to test profile sizes, anchor positions and installation sequencing against your structural model. Early coordination usually saves more than any late change to the system type.

Summary

Curtain walls are continuous, multi-storey cladding systems, while window walls are assembled floor by floor. The right choice depends on height, structure, fire strategy and construction sequence.

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