# Spider Glazing — Routels, Glass Fins and Tie Rods

> Spider glazing is point-fixed structural glazing in which each toughened glass panel hangs from bolted spider fittings, carried by glass fins, stainless tie rods or a steel or aluminium frame behind. It suits entrances, atria and lobbies where maximum transparency is the aim, and uses heat-soaked glass with holes drilled before toughening.

## What we deliver

**Point-fixed structural glazing** using spider routels, with glass fins and tie
rods as the supporting structure where the design calls for maximum
transparency.

Spider glazing has the least margin for error of any glazing system on a
project. Each panel hangs from four bolted points, holes are drilled before
toughening and cannot be changed, and there is no frame to conceal a
dimensional error. Everything has to be correct at fabrication.

## Scope of works

| Stage | What we deliver |
| --- | --- |
| Design | Wind load to IS 875 Pt 3, glass thickness, fitting selection |
| Back-up structure | Glass fin, tie rod or steel design and detailing |
| Survey | Structure surveyed before glass is ordered — holes are fixed |
| Fabrication | Hole positions set, glass toughened and heat-soaked |
| Installation | Fitting setting, articulation check, panel setting, sealing |
| Handover | Water testing, inspection, documentation |

## What drives the cost

Glass thickness, set by span and wind pressure · fitting type — countersunk
routels cost more than standard bolts and give a flush face · whether the
back-up is glass fin, tension rod or steel · panel size · height and access ·
heat soaking.

## Where projects go wrong

- **Non-heat-soaked toughened glass.** Nickel sulphide inclusions cause
  spontaneous breakage years later, over an occupied space.
- **Setting out from the building rather than the glass.** Holes are fixed at
  fabrication; the structure must be surveyed and built to match.
- **Under-designed back-up structure.** Spiders transfer the entire wind load
  into whatever is behind them.
- **Rigid fittings.** Fittings must articulate, or bending moment is forced into
  a drilled hole — the weakest point in the panel.
- **Specifying it across a full elevation.** High cost, weak thermal
  performance, difficult sealing.

## Why Hagerstone

**Facade engineering leadership** — a Director with 25+ years in premium facade
solutions, structural glazing and high-rise exterior execution, with a dedicated
20-member facade team.

**100% in-house execution** across curtain wall, spider glazing, cladding and
fenestration, so the transition from a spider-glazed atrium into the surrounding
facade is detailed by one team.

**79+ quality checkpoints** under ISO 9001 / 14001 / 45001 certification.

## Standards referenced

Design wind pressure to **IS 875 (Part 3)**. Architectural safety glass to
**IS 2553 (Part 1)** — toughened for point-fixed applications, with heat soaking
specified explicitly.

## Frequently asked questions

### Where does spider glazing make sense?

Entrances, atria, lobbies, showrooms and double-height feature elevations — anywhere maximum transparency is the point of the design. It is a poor choice for a whole building facade: cost per square metre is high, thermal performance is weaker than a curtain wall because the point fittings bridge the assembly, and sealing is harder. It works as a feature, not as a default.

### What glass is required?

Toughened, and it should be heat-soaked. The bolt holes concentrate stress at four points, which annealed and heat-strengthened glass cannot take. Heat soaking reduces the risk of spontaneous failure from nickel sulphide inclusions — a real consideration when panels hang over an occupied lobby. Holes are drilled before toughening; glass cannot be modified afterwards.

### What supports the spiders?

Something has to carry the wind load behind the glass. On modest 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. We design the back-up structure as part of the package.

## 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/services/facade-glazing/spider-glazing-systems