Before software had become commonplace at all levels of structural design and production, plans were designed and represented on paper. Common scales types were established to represent different sizes of structures and sites across different sizes of paper. The scales represent a particular relationship between the actual size to the scaled size on the paper. Architectural and Engineering scale systems simply use two different relationships between the scaled size and the actual size.
In North America, architectural scales are divided using fractions of an inch to represent one foot. For example:
| 1/16″ | = | 1’0″ |
| 3/32″ | = | 1’0″ |
| 1/8″ | = | 1’0″ |
| 3/16″ | = | 1’0″ |
| 1/4″ | = | 1’0″ |
| 3/8″ | = | 1’0″ |
| 1/2″ | = | 1’0″ |
| 3/4″ | = | 1’0″ |
| 1″ | = | 1’0″ |
| 1-1/2″ | = | 1’0″ |
| 3″ | = | 1’0″ |
Engineering scales on the other hand represent one inch as a certain number of feet. For example, a 1:10 scale means 1” = 10’:
| 1:10 |
| 1:20 |
| 1:30 |
| 1:40 |
| 1:50 |
| 1:60 |
Virtually any size structure can be accurately represented by using these scale systems. However, these systems don’t just represent scales differently, they’re also typically used for different purposes. An engineer’s scale is also sometimes referred to as a civil scale and is more useful for particularly large civil projects like bridges or roads. Engineer scale systems aren’t commonly used for residential or commercial structures. These plans are much more likely to use 1/4” or 1/8” per foot scales for average size structures.
Much of today’s construction industry is driven by software. From the initial designs of the plans in CAD (computer-aided design) software to producing materials lists with takeoff software, the plans may only ever exist in a non-physical format. Yet these same scales systems are still used throughout the process. In this way, a set of plans can be accurately read and understood in digital format as well as print format.