Most disputes about a drawing set are not about the design. They are about whether the drawing was readable, complete and consistent — whether the title block said who checked it, whether the projection angle was stated, whether a hidden edge was distinguishable from a centreline at A3. In Australia the standard that settles all of that is AS 1100, the technical drawing standard.
It is cited constantly and read rarely. This is what it actually governs, and what a set produced to it should look like when it lands on your desk.
The Parts of AS 1100
AS 1100 is a series, not a single document, and a drawing note that says only “to AS 1100” is less useful than it looks:
- Part 101 — general principles. Sheets, lines, lettering, scales, projection, sections and dimensioning. The part that governs most drawings.
- Part 201 — mechanical engineering drawing. Tolerancing, surface texture, screw threads, machining detail.
- Part 301 — architectural drawing. Building-specific conventions, symbols and annotation.
- Part 501 — structural engineering drawing. Steel and concrete detailing conventions.
A mechanical set cites 101 and 201. An architectural set cites 101 and 301. Naming the parts that apply is a small note that prevents a genuinely ambiguous drawing later.
Sheet Sizes
AS 1100 uses the ISO A series. The proportion is constant, so a drawing plots correctly on the next size down — provided the text was sized for it.
| Sheet | Size (mm) | Typical use |
|---|---|---|
| A0 | 841 × 1189 | Site plans, general arrangements |
| A1 | 594 × 841 | The standard construction sheet |
| A2 | 420 × 594 | Sub-assemblies, smaller GAs |
| A3 | 297 × 420 | Shop details, office printing, markups |
| A4 | 210 × 297 | Schedules, single components, certificates |
The practical test is the A3 test: if a set is issued at A1 but everyone reviews it as an A3 print or on a laptop, text and line weights have to survive that reduction. A drawing that is only legible at full size is a drawing that will be misread.
Line Types and Widths
Line work carries meaning, and the meaning is only readable if the widths are actually distinguishable. AS 1100 works on a ratio — thick lines roughly twice the width of thin ones — rather than fixed millimetre values for every case.
| Line | Appearance | Means |
|---|---|---|
| Continuous thick | Solid, heavy | Visible outlines and edges |
| Continuous thin | Solid, light | Dimensions, leaders, hatching, projection |
| Dashed thin | Short dashes | Hidden edges |
| Chain thin | Long-short-long | Centrelines, axes, pitch circles |
| Chain thick at ends | Heavy at terminations | Cutting planes for sections |
| Continuous thin, freehand | Irregular | Breaks and partial views |
Two widths that plot identically defeat the whole convention. This is the most common failure in sets converted from PDF or inherited from another office, where every entity arrives on one layer at one width.
Projection Angle — State It
Australia uses third-angle projection, as does North America. Most of Europe and much of Asia use first angle. In third angle the view placed to the right of the front view is the right-hand side; in first angle it is the left. On a symmetrical part the difference is invisible. On an asymmetric one it produces a mirrored component, and the mistake is usually found after machining.
The projection symbol belongs in or beside the title block on every sheet. It is two views of a truncated cone, and which side the small circle sits on is the whole message. Its absence on a set shared across borders is a real risk, not a formality.
Scales
AS 1100 uses preferred scales rather than arbitrary ratios: 1:1, 1:2, 1:5, 1:10, 1:20, 1:50, 1:100, 1:200, 1:500, 1:1000 for reduction, and 2:1, 5:1, 10:1 for enlargement. Every view carries its own scale where it differs from the sheet scale, and details are labelled with both the detail reference and its scale.
Two rules save arguments. Dimensions govern, never a measurement scaled off the drawing — which is why DO NOT SCALE appears on well-made sets. And any sheet that might be reproduced at a different size should carry a graphical scale bar, because a printed ratio is wrong the moment the sheet is reduced and a scale bar reduces with it.
The Title Block
The title block is the drawing’s metadata, and it is what makes a set auditable years later. It should carry:
- Drawing title and drawing number
- Revision letter or number, with a revision table showing what changed and when
- Scale, sheet size and projection symbol
- Drawn by, checked by, approved by — with dates
- Client and project identification
- Units, and the standards the drawing is produced to
- Status — preliminary, for approval, for construction, as-built
Two fields do the most work in practice. Status is what stops a preliminary sheet being built from. Revision history is what lets anyone reconstruct which version was on site on a given day — the question that actually gets asked when something goes wrong.
Dimensioning and Text
Dimensions in millimetres, without the unit symbol, where the drawing states that millimetres are the unit — and that statement belongs in the title block. Metres are used on site and civil drawings, again declared rather than assumed. A drawing that mixes units without saying so is the origin of a whole category of site error.
The conventions that matter most day to day: dimension each feature once, and once only; place dimensions outside the outline where they can be, with the smallest nearest the view; keep text upright and readable from the bottom or the right-hand side of the sheet; and size lettering so it survives reduction — around 3.5 mm for general annotation and 5 mm or more for titles, on a sheet that will be printed at issue size.
A Checklist Before You Accept a Set
- Title block complete, including checked-by and status.
- Projection symbol present on every sheet.
- Revision table filled in, and the revision letter matching the sheet.
- Line widths visibly distinguishable on an A3 print.
- Units declared; no drawing mixing millimetres and metres silently.
- Every view’s scale labelled where it differs from the sheet.
- Standards cited by part, not just “AS 1100”.
- No dimension repeated on two views.
Eight checks, and they catch most of what makes a set hard to build from. The current editions are published by Standards Australia.
Drawings Produced to the Standard
Consistency across a set is a drafting discipline, not a software setting — templates drift, offices differ, and inherited files carry their origin’s conventions with them. Our 2D CAD drawing work is produced to AS 1100 with title blocks, line work and annotation set up per project, and if you are unsure which file format to ask for alongside it, our guide to DWG, DXF, PDF and IFC covers that question. Get in touch with a sample sheet and we will tell you what a set to standard would change.