Technical Drawing : Labelling and annotation
In Part 1 of our technical drawing series we looked at Layout, exploring drawing sheets, title blocks and the general arrangement of our drawings. In this part of the series, we will go into more detail, looking at how we label and annotate our drawings.
It is important to remember the main objective with our technical drawing. That is to communicate our ideas or design as clearly as possible. Two things to understand here are:
Does the drawing covey what I want to be built/ created?
Does it read easily? It is neat, clearly annotated, good use of line weight, hatches etc.
There are many different ways that architects number their drawings. Although there are standards, may practices adapt the standard numbering system to reflect the needs of their own office.
You can read more about the standard drawing numbering system here:
I tend to use a simpler approach given that most of the projects I work on are residential and therefore do not have a large number of drawings compared to commercial projects.
The drawing number prefixed with the discipline designator, A for architect, or I for Interior Design and so on.
- G – General
- A – Architectural
- E – Electrical
- S – Structural
- I – Interiors
- L – Landscape
- 0 – General – notes, legends etc
- 1 – Plans
- 2 – Elevations
- 3 – Sections
- 4 – Enlarged plans, elevations, sections, interior elevations
- 5 – Details
- 6 – Schedules
So, a floor plan drawing would be A100 for example, then if you had a number of floor plans A101, A102, A103 and so on.
- A100 – Site Plan
- A101 – Ground Floor Plan
- A102 – First Floor Plan
- A103 – Roof Plan
A set of elevation drawings may be A200, A201, A202 and so on.
It is important to ensure each drawing on a drawing sheet is labelled. Beneath each drawing, you should include a title bar that contains the following information:
title of the drawing
scale of drawing
drawing sheet number of referenced drawing (where applicable, ie sections, elevations.)
Reference markers are labels on a drawing that indicated where the drawing is taken from and what it is showing. These consist of elevation markers, section markers and detail markers.
For example, you will use your floor plan to show the reader the points at which you will take an elevation, or a section line through the building. You will also use a floor plan (or section) to show junctions or areas where you will reference a detail.
As a rule, the different markers have a standard aesthetic that makes them easy to recognise.
The elevation marker is shown as a circle with an arrow pointing toward the elevation.
Inside the circle, there is a reference number or letter referring to the elevation drawing number or letter, and underneath this, is the drawing sheet number where that elevation can be found.
Elevation marker labels can be number or letters, or relate to the orientation of the elevation, ie north south east or west.
The elevation marker does not always show a reference number to the drawing sheet.
The section marker is shown slightly differently to an elevation marker with a larger arrow. The arrow shows the direction that the section is being taken. The section marker is attached to a line that runs through the floor plan showing the cut of the section.
Again, the section marker has two sets of information within the marker circle, the first is the letter or number that refers to the section, the second number underneath refers to the drawing sheet number where the section can be found.
Whether you are labelling your elevation or sections with numbers or letters, make sure you are consistent throughout.
A detail marker is similar to the section and elevation markers in that it has a drawing reference number or letter, and a reference to the drawing sheet where that detail drawing can be found.
The marker itself usually includes a box around the area showing the detail.
Key / Legend
A Key or Legend is provided to help make the drawing as clear and easy to understand as possible. A key can be used in a number of ways. It might be to show the different hatches used to represent materials and what they mean.
A key can also be used as a labelling tool, where numbers are put on the drawing and the corresponding description is written in the key.
Always keep in mind, annotation and labelling are to ensure clarity of the drawing. You might consider whether it is better to label each individual item in a drawing, or to number elements and have a key. Which one is easier to read? This will vary from one drawing to the next.
Labelling a drawing and having the text on the drawing can clutter the information. Make sure you keep the labels aligned and slightly away from the drawing to keep things clear. If you are using arrows, try to keep them all at the same angles. A good option is vertical, horizontal and 45 degree angle only if possible.
There are a number of standard line types that indicate different things on a drawing. Lines can be drawn to indicate hidden objects, cutting lines, boundaries and so on. Lines can be continuous (ie solid) or dashed. They will also vary in thickness or line weight. It is worth taking note of these line types and understanding when to use them.
Continuous lines generally represent walls, columns and other major elements, with different line weights assigned according to hierarchy of the element.
Dotted and dashed lines can indicate hidden items, or ceiling height changes, wheelchair turning circles and so on.
The following are the most common line types you will encounter.
- Boundary line
- Cutting line
- Object line
- Hidden line
- Centre line
- Dimension line
- Leader line
- Break line
Levels and Dimensions
Dimensioning provides accurate sizing on objects in the drawing. Dimension lines are used to identify exactly where the dimension begins and ends.
Generally dimensions are drawn in order from outside, starting with the overall dimension or outside dimension, then following with the smaller details in the space.
It is important to keep your dimensioning consistent in terms of both style and format. Consider why dimensions are being added to the drawing. Dimensions are added to walls, columns, doors, windows, openings, stairs and other elements of the construction. Dimensions can be taken from the frame or finished surface, this will depend on the type of drawing being produced.
Dimension lines are lighter than line weights used for walls and structural elements. The dimension line is offset slightly way from the object, and does not touch it. Arrows, dots, or ticks are used to cross the extension line with the dimension line.
Levels are added to both floor plans, sections and elevations to indicate external ground level, finished floor level, and upper story levels.