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Colorful CAD Drawings Communicate Better

Author : Michael Rountree

Modern large-format printers are just as capable of full-color output as they are of the ordinary black-and-white line drawings that most draftsmen produce. Color, when thoughtfully employed, can go a long way towards helping others to read and understand a set of drawings. My work for a commercial and residential architect in Ohio involves production of drawings which communicate a design accurately and thoroughly, whether it be to contractors, building officials, or to the Owner.

Why are monochrome drawings the industry standard?

In years past, methods of drawing reproduction required it; the term "blueprint" referred to the light-sensitive sheets which, when exposed to light, would turn blue. The ink or pencil lead on the translucent original sheet would mask areas, leaving white "shadows" against the exposed blue background. More recently, plotters were first developed with a single ink color but varying pen sizes, to achieve variation in line weight. Within the CAD program, then, the on-screen colors were an abstraction, as each color would be assigned to a different pen. Even to this day, full color reproductions such as by a printing house can cost significantly more than simple black on white. However, modern printing technology does not mandate such a premium on color inks, especially if one considers owning a large format printer and producing drawings in-house.

What can color do for me?

While the temptation might be to employ color in an aesthetic manner, creating drawings that are pleasing as art perhaps, for technical drawings this would be a mistake. Architectural floor plans, my forte, are typically layered with multiple levels of information. This can include dimensions, room and door numbers (which correlate to room and door schedules), furnishings, cabinetry, elevation and section callouts, and more. By assigning unique colors (or color ranges) to each such layer of information, it helps the reader to distinguish among them. Is that line a wall or is it a witness line for a dimension? When the walls are black and the dimensions blue, it is easy to tell.

Color can also differentiate between broad categories, such as distinguishing Existing and New features. In my office, we use green to designate the existing building, and black for the new walls, doors, etc. We also use a difference in line weight, so that color is not the only differentiator (in case someone photocopies the drawings), but this color difference makes it easy at a glance to recognize the extent of the new work. Electrical and lighting plans can show new fixtures different from existing, in a similar manner.

Elevation drawings can use color to represent finish materials, such as maroon hatching for brick or grey for shingles. This is where the color assignments can get more representational, although they still serve a legibility purpose. Some jurisdictions may require a full color rendering of the proposed project, such as for zoning approval. While a photo-realistic computer model might be an expensive proposition, simple color hatch and fill patterns on the 2D CAD drawing might serve just as well.

What does it take to develop drawings in color?

The primary requirement for color design documents is a large-format printer capable of color output. Modern inkjets use CMYK inks for full-color rendition, and some add custom inks to extend the color gamut. Technical drawings don't need photo-realism, so just about any printer will do; choose one with good speed.

The second requirement is drafting software which allows color assignments to drawn elements. It must treat color as a property to be printed, rather than as a proxy for line/pen weight. Some CAD packages can display vivid colors on screen but then convert everything to black on its way out to the printer. I use Ashlar's Graphite, in which color, line weight, and line style are all separate properties of each element, and can be assigned regardless of layers or membership in groups or symbols.

Another requirement is that you have a coherent approach to your use of color, which might be conditioned on the first two requirements. If the printer you use does a poor job of rendering greens so that various shades can be distinguished, this may limit your choices to just one or two greens. If the software you use comes with a fixed palette to which one cannot add, then you will have to strategize around that limitation. Your color strategy might be to have colors represent materials, such as black for studs and brown for brick veneer. You may wish to set aside certain colors, reserving it for a purpose, such as red being used only for revisions and their tags.

Elements that are the same color will tend to be perceived as belonging together, whereas elements of different colors will come across as unique or separate items. Use this to your advantage. As an example, consider a range top in a kitchen plan; the range might be composed of many lines and arcs, but in essence it is just a large boxy object that the other cabinets must fit around. By making all range elements the same color, distinct from the cabinets and countertop, it becomes easy to see the important edges where they meet, while not getting lost in what may be extraneous detail.

Finally, consider that at some point in time, your gorgeous color drawings are likely to sit on top of a copier, which will reduce them to a black and white copy. Thus, it is good to reinforce distinctions made by color with other qualitative differences, such as line weight or line pattern. Certain colors, too, may be legible on the color print but become too faint on the monochrome copy, such as light greens or blues. Be sure to test your color scheme for legibility when copied.

Author's Resource Box

Mike Rountree works for a residential architect in Ohio where his color construction documents help the home owner, contractors, building officials, and other design consultants to communicate throughout the architectural process.

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Tags:   CAD, drawings, construction documents, color

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Submitted : 2011-05-19    Word Count : 987    Times Viewed: 2055