Spider Glazing: Frameless Glass Held on Point Fixings
Spider glazing supports glass on stainless-steel arms — spiders — bolted through holes drilled in the panel corners, so the glass is carried at points rather than along its edges. Removing the frame is what makes an atrium or lobby read as glass with almost nothing holding it up.
By Dhruv Agarwal · · 2 min read
Why it matters on a facade project
Spider glazing is chosen for one reason: it is the most visually transparent way to enclose a space. On a hotel lobby, a showroom or a corporate atrium, that first impression is the whole point of the specification.
It also has the least margin for error of any glazing system on a project. Each panel hangs from four bolted points, the glass is drilled before toughening and cannot be modified afterwards, and there is no frame to hide a dimensional mistake. Everything has to be right at fabrication.
How it is specified in practice
| Parameter | Typical position | Why |
|---|---|---|
| Glass | Toughened, heat-soaked, usually 10-19mm | Point loads at the bolt holes; heat soak reduces spontaneous failure risk |
| Fitting | 2-arm, 4-arm or countersunk routel | Countersunk gives a flush face; standard bolts sit proud |
| Back-up structure | Glass fins, tension rods, or steel | Must resist full wind load; drives the visual character |
| Articulation | Fittings articulate at each point | Prevents bending stress being forced into the glass |
| Hole tolerance | Drilled pre-toughening, tight tolerance | Glass cannot be drilled or cut after toughening |
| Joint | Weather silicone between panels | The joint is a weather seal only, never structural |
Common mistakes
- Using non-heat-soaked toughened glass. Nickel sulphide inclusions cause spontaneous breakage years later. On a lobby facade, that is a safety issue as much as a replacement cost.
- Setting out from the building rather than the glass. Holes are fixed at fabrication. If the supporting structure is not surveyed and built to match, panels will not fit, and the glass cannot be adjusted.
- Under-designing the back-up structure. The spiders transfer the entire wind load into whatever is behind them. Glass fins and tie rods must be designed for the pressure from IS 875 Part 3, not sized by eye.
- Using rigid fittings. Fittings must rotate. A fixed connection forces bending moment into a drilled hole, which is precisely where glass is weakest.
- Specifying it across a whole elevation. Thermal performance is poor and cost is high. It works as a feature, not as a default.
Where Hagerstone uses it
Spider glazing with routels, glass fins and tie rods sits within our in-house facade scope, alongside curtain wall, cladding and fenestration — so the point fittings, the back-up structure and the surrounding facade are detailed by one team rather than coordinated across three vendors.
Standards referenced
Design wind pressure follows IS 875 (Part 3). Architectural safety glass requirements sit under IS 2553 (Part 1); for point-fixed applications this means toughened glass, and heat soaking should be specified explicitly.
Standards referenced
- IS 875 (Part 3) — Wind loads on buildings
- IS 2553 (Part 1) — Safety glass — architectural