Spider Glass Facade: What It Is & How It Differs from Curtain Wall

If you have looked at large glass entrances, luxury lobbies and the atriums of commercial complexes, you have probably seen a facade whose large panes are embraced by no aluminum frames at all — as if the glass were floating in the air. That is spider glazing: a system that fixes the glass to the structure behind the facade with point-fixed metal connectors, creating the maximum transparency possible.

The heart of this system is the spider arm: a component made of 304 or 316 stainless steel which, with four (or two) movable arms, clamps each pane to the structure at its four corners. The glass is tempered, usually 10 to 15 mm thick, to provide the necessary resistance against wind and impact. The holes are drilled at the factory with CNC machines, and each hole carries a rotule and a gasket that both hold the glass and allow the movement caused by thermal expansion and wind load — without these rotules, the glass would crack sooner or later.

The more important question is what the glass is actually fixed to. There are two common answers: a steel structure (stainless or galvanized) and fin glass. In the fin-glass system, instead of steel columns blocking the view, vertical glass blades (fins) of tempered laminated glass carry the vertical and wind loads, and from the inside you see a completely glassy, frameless view. The choice between a steel structure and fin glass depends on the spans, the height and the architecture of the project, and must be made with structural calculations — not on the basis of taste.

Now the main question: how does spider glazing differ from a curtain wall? In a curtain wall, the glass sits inside aluminum frames and the entire system is hung on the structure like a curtain; waterproofing is handled through the gaskets and the drainage system inside the frame, and each pane can be double-glazed. In spider glazing, the glass is fixed at points and the sealing between the panes is done with structural silicone. The result: spider gives more transparency and visual impact, but the curtain wall offers better thermal performance and all-round waterproofing.

For this reason, the choice between the two is usually not the question 'which is better?' but 'which is right for which part of the project?'. For a full-glass floor envelope, the curtain wall is the right choice because it provides thermal insulation, continuous waterproofing and glass variety (reflex, laminated, double-glazed). For the main entrance, a double-height lobby, an atrium, a glass roof and storefronts that demand maximum transparency, spider is the right option. In many of our projects — including parts of large Tehran projects — the two have been built side by side: spider for the grand entrance, curtain wall for the body of the facade.

A technical point rarely mentioned anywhere: the cost of maintenance. Because of its full transparency, spider shows every stain and smudge sooner, and after some years the silicone between the panes may need spot repair. The curtain wall has its own gaskets, which are inspected at long intervals. Neither system is 'absolutely trouble-free'; but both, if executed with the right details, have a very long service life. The real issue is the quality of the detail and the execution — not the type of system.

When choosing a spider contractor, check these items: real executed references with project photos (not renders); the grade of stainless steel used in the connectors (304 or 316 — near the sea, 316 is essential); a track record of CNC drilling of glass; and the structural anchoring detail. The smallest mistake in a hole or a rotule means breaking a large and expensive pane. As a team that has executed spider glazing for years on heavy projects from Iran Mall to office complexes, we calculate the detail of every project separately.

In summary: spider is the crown of entrances, and the curtain wall is the backbone of modern glass facades. If your project wants a special entrance, an atrium or a floating glass facade, build the spider glazing with an experienced team; if you want a full-envelope facade with good energy performance, go for the curtain wall — and if you are not sure, a short technical consultation can remove a mistake worth hundreds of millions from your project. Our executed details are freely viewable in the library on our website. For a free technical review, contact Namakaran Fakher Engineering Co.