What is Scale?

Definition of Scale in Construction

The scale of a drawing, sketch, etc., is the size of the document.

Construction documents are normally developed in what is known as an architectural scale. The architectural scale references inches and feet. If the scale is drawn in 1/4 inch scale, this means that for every 1/4 inch on the paper, one foot of actual construction product, component or building is drawn. The scale is a reduced measurement of the actual.

What is helpful when viewing scaled documents is that the dimensions can be identified using an actual ruler placed on the document itself. If the scale is 1/4 inch and the length of the line is 4 inches, the actual dimension of the building, construction component, or whatever is being depicted is 16 feet. Many times the architectural, structural, mechanical and electrical documents are drawn in an architectural scale.

However in many instances, the site documents, or civil drawings are detailed or drawn in an engineering scale. The engineering scale is based on, not inches, but portions of a foot. For example, a 10th scale, is a scale that represent 10 feet to the inch. A 20th scale, is a scale that represents 20 feet to the inch. In this manner, the normally larger site documents can fit on standard drawing size paper nor do they have to be cut ( broken up into several drawings ) as many times in the presentation.

The scale is an important piece of information and critical when reading construction documents. During the estimate period of the project, it is extremely important that the proper scale be used, due to its affect on the outcome of the estimate. If a 1/2 inch scale was intended, and the estimator made a mistake by using a 1/4 inch scale, the estimate would be twice as high as what the documents intended. Scale is critical, and the duplication of documents on printers and copy machines must be carefully monitored, due to the actual size depiction of the drawing. If the document is copied at 80% of actual size, all the scaled dimensions will be 80% of the intended size. This could be a disaster in the field during layout or in the estimators office, as a proposal is being developed.

There are several different take off scales, equipment, apparatus, computers, etc. that can be used to determine quantities on a document that has been drawn to scale. Obviously the computer screen is the most handy, however, a string and a tape measure can still offer some valuable information. By utilizing the scale of a document, the contractor can visualize the project and its subsequent dimensions.

An experienced contractor and someone who is experienced with using scaled documents, will be able to identify a dimensional issue easily in the field, hopefully, prior to a substantial error being made regarding the size of the project.