Lesson 3.4
Dimensions You Must Know Cold
The working reference: doors, corridors, counters, stairs and clearances, in metric and imperial, with the codes that govern them. The cheat-sheet you'll return to for years.
Start hereMost of architecture runs on perhaps forty dimensions. Know them cold and you can sketch a workable plan anywhere, in any unit, without looking anything up.
This lesson is that list — organised, both systems, code-aware. Print it. Tape it to your wall.
01 — The working set
The dimensions, organised
These are starting values, in both systems. Where a figure is code-governed, that's flagged — because, as you learned in 0.3, the exact minimum is a regional dialect. Treat metric as the spine and imperial as its translation. The interactive below lets you flip through the working set, category by category.
| Element | Metric | Imperial | Note |
|---|---|---|---|
| ◆Single door (internal) | 800–900 mm | 2'-8" – 3'-0" | Code-governed min. |
| Door height | 2000–2100 mm | 6'-8" – 7'-0" | — |
| Accessible door (clear) | ≥850 mm | ≥32" | Code-governed |
| Window sill (typical) | 900 mm | 3'-0" | — |
Flip through the working set, category by category. Rows marked ◆ are the 'spine six' worth memorising; metric is the spine, imperial its translation.
02 — Doors & openings
Doors, windows and the openings a body passes
Door widths and heights are the most-quoted figures in the set, and the lower end of the door width is code-governed for access. Window sill heights track the seated and standing eye levels from 3.2.
| Element | Metric | Imperial | Note |
|---|---|---|---|
| Single door (internal) | 800–900 mm | 2'-8" – 3'-0" | Code-governed min. |
| Door height | 2000–2100 mm | 6'-8" – 7'-0" | — |
| Accessible door (clear) | ≥850 mm | ≥32" | Code-governed |
| Window sill (typical) | 900 mm | 3'-0" | — |
03 — Circulation & stairs
Moving through, and moving up
Corridors, passing widths and the wheelchair turning circle govern how a body moves horizontally; risers, treads and handrails govern the climb. Most of these are code-governed for safety and access — verify the local minimum.
| Element | Metric | Imperial | Note |
|---|---|---|---|
| Corridor (residential) | 900–1100 mm | 3'-0" – 3'-7" | Code min. varies |
| Corridor (public) | ≥1200 mm | ≥4'-0" | Code-governed |
| Two people passing | ~1200 mm | ~4'-0" | — |
| Wheelchair turning circle | 1500 mm | 5'-0" | Code-governed |
| Stair riser (height) | 150–185 mm | 6" – 7¼" | Code-governed max. |
| Stair tread (going) | 250–300 mm | 10" – 12" | Code-governed min. |
| Stair width (residential) | ≥900 mm | ≥3'-0" | Code min. |
| Handrail height | 900–1000 mm | 3'-0" – 3'-3" | Code-governed |
04 — Kitchen & bath
The fixtures, traced to the body
Counter and basin heights sit at elbow height; upper cabinets start where a hand reaches comfortably; walkways and the WC front clearance let a body turn and use the fixture. Every figure here traces straight back to the baseline body of 3.2.
The code note: the 'code-governed' figures vary by region — NBC (India), IBC/ADA (USA), Eurocodes (Europe). The ranges here are typical starting points; the exact minimum for a real project comes from the local code edition. You'll compare these codes directly in Module 5.
| Element | Metric | Imperial | Note |
|---|---|---|---|
| Counter height | 850–950 mm | 2'-10" – 3'-1" | — |
| Counter depth | 600 mm | 2'-0" | — |
| Upper cabinet start | 1350–1500 mm | 4'-5" – 5'-0" | — |
| Kitchen walkway | 1000–1200 mm | 3'-3" – 4'-0" | — |
| WC clearance (front) | 600 mm | 2'-0" | Code-governed |
05 — How to use this
Memorise the spine, look up the rest
You don't need all of these by heart immediately. Memorise the spine six — single door 900, counter 900, corridor 1000, riser 175, tread 275, turning circle 1500 — and you can rough out almost any plan. The rest you'll absorb through use, and verify against code when a dimension is critical to safety or access.
Notice how cleanly the metric and imperial columns track each other, and how often the figure traces straight back to a body dimension from 3.2. This table isn't a list to cram — it's the body, made practical.
The 'code-governed' figures vary by region — NBC (India), IBC/ADA (USA), Eurocodes (Europe). The ranges above are typical starting points; the exact minimum for a real project comes from the local code edition. That's the same grammar-versus-dialect distinction from Module 0: a stair must let a body climb safely (universal), but the exact maximum riser is set by the local code (dialect). You'll compare these codes side by side — watching a corridor redraw itself to each standard — in Module 5.
15 minutes
- Cover the imperial column and convert five metric figures in your head. Then check.
- From memory, write the 'spine six': door, counter, corridor, riser, tread, turning circle — in metric.
- Sketch a small bathroom plan at 1:50 using only dimensions from this table. Label each and note which are code-governed.
- Download the worksheet and keep the cheat-sheet somewhere visible.
Key terms — added to the Drawing Atlas
- Spine six
- The core dimensions worth memorising: single door 900, counter 900, corridor 1000, riser 175, tread 275, turning circle 1500.
- Code-governed dimension
- A dimension set as a legal minimum or maximum by a building code (door, corridor, stair, clearances); varies by region.
Check yourself
2 quick questions — pick an answer to see why.
Q1A typical single internal door width is around:
Q2Which of these dimensions is typically code-governed (a legal minimum/maximum)?
- Roughly forty dimensions run most of architecture — known cold, you can sketch anywhere.
- Metric and imperial track closely; both trace back to the body dimensions of 3.2.
- Code-governed figures (door, corridor, stair, clearances) vary by region — verify the local minimum.
- Memorise the spine six; absorb and look up the rest.
You can size any element from the body. Now it's time to put bodies into space on paper — to cut a building into plan, section and elevation and read all three.