# 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.

## 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.

## Frequently asked questions

### What glass can be used in spider glazing?

Toughened glass only, and normally heat-soaked. The bolt holes concentrate stress at four points, which annealed or heat-strengthened glass cannot take. Heat soaking matters because toughened glass carries a small risk of spontaneous failure from nickel sulphide inclusions, and a panel hanging over a lobby is the worst place for that to happen.

### What holds the spiders themselves?

Something has to resist the wind load behind the glass. On smaller spans that is a steel or aluminium structure. On tall atria it is usually glass fins — vertical glass beams — or a tension system of stainless tie rods and cables, which is what keeps the assembly visually light.

### Is spider glazing suitable for a full building facade?

Rarely, and it is usually the wrong tool. It is expensive per square metre, thermally weaker than a curtain wall because the point fittings bridge the assembly, and harder to seal. It belongs on entrances, atria, lobbies and showrooms where the visual effect justifies it — not on twenty floors of office.

## Sources

- [IS 875 (Part 3)](https://standards.bis.gov.in/website/published-standards/department-wise) — Wind loads on buildings
- [IS 2553 (Part 1)](https://standards.bis.gov.in/website/published-standards/department-wise) — Safety glass — architectural

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Source: https://hagerstone.com/glossary/spider-glazing