# Caged ladder (ISO 14122-4)

Fixed steel ladder after ISO 14122-4: 65 × 12 flat-bar stiles at 450 mm, Ø25 rungs at 300 mm, stiles extended 1.1 m above the landing, a safety cage (hoops from 2.3 m, five vertical bars) and stand-off brackets. A single flight is used up to 10 m of climb; above that the climb is split into staggered flights of at most 6 m with bracketed rest platforms. Optional top landing on posts with handrails and a self-closing gate. Foot at the origin on y = 0; rungs in the plane z = 0 with the climber and cage on +Z; the structure face and the landing are at z ≤ −0.2, the landing walking surface at y = height.

**Standards:** ISO 14122-4, EN ISO 14122-1, NORSOK C-001, OSHA 1910.23

## Installation

```bash
npx -y https://decktwin.com/cli/deck-twin-0.2.2.tgz add ladder
```

Copies `structure/ladder.tsx`, any helper files it imports and the shared `lib/` into `src/components/deck-twin/`. Needs `three`, `@react-three/fiber` and `@react-three/drei`.

## Usage

```tsx
import { Canvas } from '@react-three/fiber'
import { OrbitControls } from '@react-three/drei'
import { Stage } from './components/deck-twin/lib/stage'
import { Ladder } from './components/deck-twin/structure/ladder'

export default function Scene() {
  return (
    <Canvas shadows camera={{ position: [8, 5, 9], fov: 35 }}>
      <Stage>
        <Ladder />
      </Stage>
      <OrbitControls makeDefault />
    </Canvas>
  )
}
```

## Props

| Prop | Type | Default | Range |
| --- | --- | --- | --- |
| `height` | `number (m)` | `4.5` | 1 – 20 |
| `cage` | `boolean` | `true` |  |
| `landing` | `boolean` | `true` |  |
| `landingDepth` | `number (m)` | `1.2` | 0.8 – 2.5 |
| `finish` | `"galvanised" \| "painted"` | `"galvanised"` |  |
| `...group` | position, rotation, scale… |  |  |

## P&ID

Elevation: two stiles with rungs and hoops of the safety cage; in plan, a short pair of lines with a semicircle (the cage) against the platform edge, labelled LADDER.

Layout plan convention (structural / plot plan drawings); ISO 14122-4

A stair has an inclined flight with an UP arrow; a ladder is vertical. Not on P&IDs.

## Typical suppliers

Fabricated to project specification. The geometry is generic and sized from public standards. It is not vendor CAD.

## Source

`structure/ladder.tsx`. This is the component file only: it imports shared code, so install it with the command above rather than pasting it alone. https://decktwin.com/r/ladder.json has every file.

```tsx
// Fixed caged ladder after ISO 14122-4: flat-bar stiles, rungs at 300 mm, safety cage, staggered flights with rest platforms over 6 m, top landing with self-closing gate.
import type { Kit, MatKey } from '../lib/kit'
import { KitMesh, useKit, type GroupProps } from '../lib/mesh'
import { ladderRun, landing } from './_access'
import { bar, gate, railRun } from './_steel'

export interface LadderProps {
  /** foot to top landing, m */
  height?: number
  cage?: boolean
  /** top landing on posts (otherwise the ladder is wall-bracketed to a structure at z = -0.2) */
  landing?: boolean
  landingDepth?: number
  finish?: 'galvanised' | 'painted'
}

export const defaults = {
  height: 4.5,
  cage: true,
  landing: true,
  landingDepth: 1.2,
  finish: 'galvanised' as 'galvanised' | 'painted',
}

type P = typeof defaults

export function Ladder(props: LadderProps & GroupProps) {
  const { height, cage, landing: hasLanding, landingDepth, finish, ...group } = { ...defaults, ...props }
  const data = useKit((k) => build(k, { height, cage, landing: hasLanding, landingDepth, finish }), [height, cage, hasLanding, landingDepth, finish])
  return (
    <group {...group}>
      <KitMesh data={data} />
    </group>
  )
}

export default Ladder

const SO = 0.2

function build(k: Kit, p: P) {
  const mat: MatKey = p.finish === 'painted' ? 'safetyYellow' : 'galvanised'
  const H = Math.max(1, p.height)
  const [lo, hi] = ladderRun(k, 0, 0, H, 0, { mat, cage: p.cage, standoff: SO })
  if (!p.landing) return
  const x0 = lo - 0.25
  const x1 = hi + 0.25
  const zb = -SO
  const za = zb - Math.max(0.8, p.landingDepth)
  landing(k, x0, x1, za, zb, H, { post: 'SHS 100x100x6.3', rails: [true, true, true, false], mat })
  // front rail with the ladder opening and a self-closing gate
  const g = 0.35
  railRun(k, [x0 + 0.03, H, zb - 0.03], [-g, H, zb - 0.03], { startPost: false })
  railRun(k, [g, H, zb - 0.03], [x1 - 0.03, H, zb - 0.03], { endPost: false })
  gate(k, [-g, H, zb - 0.03], [g, H, zb - 0.03])
  // horizontal struts between the front posts carry the ladder and rest-platform brackets
  for (let y = 0.6; y < H - 0.3; y += 2) bar(k, [x0 + 0.1, y, zb - 0.05], [x1 - 0.1, y, zb - 0.05], 'L60x60x6', mat, [0, 0, 1])
  // step-off plate between the stiles and the landing edge
  k.box(mat, [0.44, 0.01, SO + 0.03], [0, H - 0.005, -SO / 2 + 0.01])
}
```