What Is Scale And Why Is It Important For Your Site Plan?

What Is Scale And Why Is It Important For Your Site Plan?

The significance of “scale” is all around us. From the homes we live in to the skyscrapers we stand in awe of, every one of these structures started as a piece of land and a dream. How did these dreams become reality? In this article, we explore how “scale” is vital to developing these structures and how important a site plan scale is for each of our clients. We also compare an engineer scale vs. an architect scale and discuss what the difference is.

What is scale?

In drafting, architecture, and engineering, the term “scale” has two meanings.

As a concept, scale is a standard range of values forming a standard system for measuring or grading something. How does this translate into a design? These dimensions are used by a drafter to accurately represent a real, full-size object in a drawing or physical model while retaining the proportions of the original. A scale drawing is like taking the original and shrinking it down proportionally.

As a physical object, scale is also a ruler used to draw and measure architectural and engineering plans. There are two types of scales or rulers: an engineering scale and an architect scale.

Architect's scale

The architect

Architects and builders use the architect's scale to obtain measurements from scaled drawings of buildings and other structures. It is typically three-sided with 11 scales or flat with four scales. It is available in lengths ranging from four to 36 inches, although 12-inch models are most common.

Once made primarily from wood, most architect's scales are now made from plastic, aluminium, and stainless steel.

How to read an architect’s scale

An architect's scale is read from the left or right side depending on the scale used.

It uses fractions and has the following dimensional relationships:

3/32 = 1 foot

3/16 = 1 foot

1/8 = 1 foot

1/4 = 1 foot

3/8 = 1 foot

1/2 = 1 foot

3/4 = 1 foot

1 inch = 1 foot

1 1/2 inches = 1 foot

Common scales for a triangular architect's scale are 16 (full), 3, 1-1/2, 1, 3/4, 1/2, 3/8, 1/4, 1/8, 3/16, 3/32. Major divisions of each scale represent feet which are further subdivided into 12ths or 16ths. A scale labeled 1/8 translates to 1/8 inch = 1 foot or 1/96 scale. The 16 or full scale is a standard ruler with each mark representing 1/16 inch.

How to use an architect's scale

There are three key steps to using an architect’s scale.

  • Step 1: Determine the scale used in the architectural drawing you’re reading — this can usually be found in the legend

  • Step 2: Find the corresponding scale on your ruler — Most triangular scales have two rows of numbers on each edge, one on top of the others. Let’s say the scale says “1/4” at one end and “1/8” at the other. The row of numbers that starts with zero closest to the scale marking are the numbers that correspond to that scale. In the example below, the top row corresponds to the “1/8” scale.

  • Step 3: Read the drawing — Place the zero on your object and read the mark where it ends. If it ends on the “8” mark on the scale, then the object is 8 feet long.

an architect

Note: there are smaller gradations to the right of the zero on each scale. These are fractions of an inch and allow you to measure fractions of a foot. If, for example, the end of the object doesn’t fall on a round number, simply move the ruler back so a smaller gradation marks the start of your object, rather than the zero. You might then read that the object is 8.5 feet long. 

Engineering scale

The engineer's scale, also known as a civil scale, is used for measuring length and transferring length measurements at different scales or proportions of actual length. It is triangular in cross-section with each of the three faces containing two different scale markings for a total of six scales.

In North America, the scales are labeled 10, 20, 30, 40, 50 and 60, with the graduations representing decimal fractions of an inch. Thus, one inch on a drawing equals between 10 to 60 feet.

The engineer's scale is usually made from plastic and is slightly over 12 inches long, but with only 12 inches of markings, leaving the ends unmarked. The extra length accounts for wear and tear over time and prevents the end ticks from wearing off.

How to read an engineering scale

To read an engineering scale, start by selecting the scale on the ruler that matches the scale on the plans. If, for example, the plan specifies that one inch equals 30 feet, then you would use the edge of the ruler marked “30” to make your measurements.

To measure the object, align your engineering ruler with the edge of said object on the plan. Take the measurement, then multiply it by 10 to calculate an accurate distance. If, for example, your measurement reads “5”, the actual length of the object is 50 feet.

Engineer scale vs architectural scale

So, what is the difference between an engineer scale and an architectural scale? Although similar in appearance to an architect’s scale, the engineering scale is designed to be more precise and has a decimal scaling scheme whereas an architect's scale uses fractional scaling. It is designed to only be read from left to right. An architect's scale can be read from either the left or right side.

Engineer scale

Architectural scale

More precise

Less precise

Decimal scaling scheme

Fractional scaling

Read from left to right

Read from either the left or right side

Common site plan scales

Remember that dream and a piece of land? Having the correct scale will directly determine how walls become rooms and dirt becomes roads.

Scale drawings assign each object the same scale compared to the actual objects. The space outlined on a scale drawing is also reduced by the same ratio as the objects included in the plan. A site plan often follows a ratio of 1:500 or 1:200, which is equivalent to one inch = 40 feet and 1/16 inch = 1 foot.

Site plan scale

Scale and your site plan

If a drawing isn't to scale, there's no guarantee that each object on the plan will fit into the real space. An accurate scale drawing lets you see exactly how each component will fit and how much space you'll have, both empty and filled. Whether you are addressing space concerns, adding or rearranging components or even working on multiple designs, scale will always play a key role in the planning of your project.

FAQ Answer
What factors should be considered when choosing between an engineer's scale and an architect's scale? The choice between an engineer's scale and an architect's scale depends on the type of measurements required. Engineer's scales are better for projects requiring decimal measurements, like civil engineering projects. Architect's scales are suitable for designs where fractional measurements are used, such as in building and room designs.
How can inaccuracies in scale affect the outcome of a construction project? Inaccuracies in scale can lead to significant problems in construction projects, including misfitting structures, incorrect material estimates, and overall project delays. Ensuring accurate scaling from the design phase is crucial to aligning the construction elements as planned.
Are there digital tools available to help with reading and using these scales? Yes, there are digital tools and applications that can assist in reading and using architectural and engineering scales. These tools often include features for automatic scaling, conversion between different scales, and integration with CAD software for precise design and measurement.
How often should scales be calibrated or checked for accuracy? Scales should be regularly checked for accuracy, especially in professional settings where precise measurements are crucial. Calibration frequency might depend on usage frequency and environmental factors that could affect the scale's accuracy, such as temperature and humidity.
What is the most common scale used in residential building site plans? In residential building, a common scale used in site plans is 1/4 inch = 1 foot. This scale helps in detailing while keeping the drawing manageable and clear.
Can different scales be used within the same project? If so, how is consistency maintained? Different scales can be used within the same project for various details. Consistency is maintained by clearly marking the scale used on different drawings and ensuring that everyone

Do you need help drawing your site plan? Speak to MySitePlan today to see how we can help. 

This article was originally published on 2018-09-20 by Heidi Chandler. It was updated by Ryan Crownholm on 2024-04-16 to provide more information to the reader.

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  • Ryan Crownholm