Orient the sheet

The lesson

A drawing sheet is a document before it is a picture. Somebody rolls it out on a table in a trailer and the first thing they look at is not the building, it is the edges. Five facts live out there, and until you have all five you cannot trust a line in the middle: which sheet this is, what the drawing is called, which way is north, what scale it is drawn at, and when it was issued and whether it has changed since.

Build that habit before anything else. Nearly every expensive mistake starts with somebody reading the right thing on the wrong sheet. A superseded print looks exactly like a current one. A plan rotated to fit the paper looks exactly like a plan that is not rotated. A half size print looks exactly like a full size print until you put a rule on it. The only defence is a fixed opening routine, and it takes about fifteen seconds.

Start in the title block, the tall strip down the right edge. It is the same on every sheet in the set because it is a stamp rather than a drawing: project name and address, owner, architect, consultants, who drew and who checked, issue status and date, a revision table, and in the largest type on the paper, the sheet number. That number is set big and low on purpose, because sheets get stacked and the corner is all you can see when they are.

The drawing title is a different thing in a different place. It sits under the drawing, usually underlined, with a number in front of it and a bar scale beneath. That number is the drawing number on this sheet. One sheet can carry several drawings, so a callout names both: drawing 2 on sheet A-501 is written 2/A-501. Reading the sheet number for the drawing number is how a beginner ends up on the right sheet looking at the wrong picture.

North belongs to the drawing, not to the sheet, which is why the arrow is drawn beside the plan and not in the title block. Two plans on one sheet can be rotated differently and each carries its own arrow. Plans get turned to fit the paper, so until you have found the arrow the words left and right mean nothing, while north and south mean everything: the elevations, the schedules and the specifications all speak in compass directions.

Scale is stated twice, for two different reasons. The title block states it in words, which is the intent. The bar scale under the drawing states it as a drawn object, which is the truth about the paper in your hands. Print a sheet at half size and the words still say one eighth of an inch while the bar has quietly shrunk to match. Put a rule on the bar before you scale anything off a print.

• The scale note in the title block is the drafter's intent, and it can be wrong about the paper in front of you.
• The bar scale is drawn at the scale of the view, so it shrinks with the print and cannot lie about it.
• A view at a different scale from the rest of the sheet says so under its own title, with its own bar.
• A drawing marked not to scale is a diagram of relationships, and measuring it means nothing.

The last fact is time. A set is issued on a date with a status, and the status matters as much as the date: issued for bid, issued for permit and issued for construction are three different documents, and a bid set is not something to build from. After issue, changes arrive as revisions, recorded in three places at once. A cloud answers where. A numbered triangle answers which revision. The revision table answers when and what.

One more habit belongs here because it saves an argument later: read the general notes before you read the drawing. On this sheet they sit in a column beside the plan, and one of them tells you what face the dimensions are taken to. That sentence changes the meaning of every number on the sheet, and the drawing states it once rather than repeating it at each string.