The Fundamentals of Drafting

The purpose of drafting is to display your design as a two-dimensional (2D) representation on a sheet of paper. Since you might have a problem fitting a 500-foot long strip mall on your drafting table, you'll need to use a ratio between the actual size of your structure and a smaller dimension on the sheet. This is referred to as scale.

How does Scale Work?

In general, an inch — or segment of an inch — is used for measuring on your page and it is equated to a real-world size. For example, a common architectural scale is 1/4" = 1'-0". This is read as: "one-quarter of an inch equals one foot." If the front wall of your structure is 20 feet long, the line representing that face on your page will be five inches (5") long. (20 x 0.25 = 5). Drafting this way ensures that everything you draw is proportional and will fit together in the real world.

Different design industries use different standard scales. When working with civil engineering drawings, scales are in the full inch format, i.e. (1" = 50'), while architectural and mechanical plans are more often done in fractional format (1/2" = 1'-0"). Scales can be done in any unit of linear measure: feet, inches, meters, kilometers, miles, even light years, if you happen to be designing your own Death Star. The key is to pick a scale before you begin drafting and use it for the entire plan.

Dimensioning

While it's important to draw objects in a design document to scale, it's not really feasible to expect people to measure every distance on your plan with a ruler. Instead, it's customary to provide graphic notes on your plan showing the length of all constructed objects. Such notes are referred to as "dimensions."

Dimensions provide the most basic information from which your project will be built. How you dimension your plan depends, once again, upon your design industry.

In architecture, dimensions are usually linear and drawn as a line, with the dimension written in feet/inches above it. Most dimensions have "tick" marks at each end to show where it begins or ends. In mechanical work, the dimensions are often circular, showing radial distance, diameters of circular components, etc. while civil work tends to use more angular notations.

Annotation

Annotation is adding text to your drawing to call out specific items that require additional explanation. For example, in a site plan for a new subdivision, you would need to label the roads, utility lines, and add lot and block numbers to the plan so there's no confusion during the construction process.

An important part of annotating a drawing is using a continuous size throughout for similar objects. If you have several roads labeled, it's important that each is labeled with a text of the same height or, not only will your plan look unprofessional; it can create confusion when people equate larger size with greater importance for a particular annotation.

A standard method of drafting text on plans was developed in the days of manual drafting, using lettering templates called Leroy Lettering Sets. The basic height of Leroy text begins with a standard height of 0.1" and is called an "L100" font. As your annotation height goes up/down in 0.01" increments, the "L" value changes as shown:

• L60 = 0.06"
• L80 = 0.08"
• L100 = 0.1"
• L120 = 0.12"
• L140 = 0.14"

Leroy fonts are still used on modern CAD systems; the only difference is that the Leroy height is multiplied by the drawing scale in order to calculate the final printed text height. For example, if you want your annotation to print as an L100 on a 1"=30' plan, multiply the Leroy size (0.1) by the Scale (30) and obtain a height of (3), hence the actual annotation needs to be drawn at 3 units in height to print at the 0.01" height on your final plan.

Plan, Elevation, and Sectional Views

Construction documents are graphic representations of real-world objects, so it's necessary to create multiple views of a design to show others what's going on. Typically, construction documents make use of the Plan, Elevation, and Sectional views:

• Plans — looking at the design from the top down (aerial view). This shows the linear interaction between all objects within the project and includes detailed dimensions and extensive annotation in order to orient all the items that need to be built within the project. The items that are shown on the plan vary from discipline to discipline.
• Elevations — looking at the design from the side(s). Elevations are used primarily in architectural and mechanical design work. They present a scaled vertical view of the design as if you were standing directly in front of it. This lets the builder see how items such as windows, doors, etc. are to be located in relation to each other
• Sections — lets you see a design as if it had been cut in half. This allows you to call out individual structural components of the design in great detail and to show exact construction methods and materials that are to be used.

There you have the basics of becoming a drafter. Sure, this is just a simple introduction but if you keep these concepts firmly in mind, everything you learn from here on out will make a lot more sense to you.