More than 50 pages longer than the previous edition, Sign Gallery 6 presents recentSigns of the Times competition winners, honorable mentions, and others in this expanded edition of electric ...
Some aspects to consider when designing channel-letter signs
From my business as an expert witness/investigator, I see every way channel letters can fail, usually through improper engineering. Thus, I’ll share the most important points to consider when designing them to avoid those failures.
Historically, the channel letter was devised for “electrical” signs to avoid the blur produced by multiple, extremely bright, points of light that radiated from the lightbulbs. Without a “channel,” the light from one letter spread into the next, rendering the text almost unreadable.
To remedy this, a metallic reflector that was fitted onto the sidewalls “returned” the light into the origina¬ting letter. The next step, channel letters with a faceplate (colored acrylic), produced a uniformly lit surface.
In this column, I can only address a few of the many aspects to consider in engineering channel letters. So, I’ll focus on fundamental considerations.
For the mechanical layout, the sign’s location (besides its size and design) plays a prime role. Indoor locations are dry (which determines what electrical components to choose) and don’t incur wind or snow loads. If the channel letters won’t be mounted flush on a wall, the support structure must bear the weight of the installation itself and also, for canopy and rooftop installations, the additional shear force of a wind load.
With large, covered letters, you must consider thermal expansion of the plastic face material, which, for 10-ft.-tall (or -wide) letters, can be approximately an inch between hot summer and cold winter days. If the return can’t accommodate the expansion without placing too much force on the face, you must include some expansion joints.
If an approved structural engineer doesn’t calculate the wind load and, especially, the required strength of the supporting roof or canopy, severe damage to life and property can result. If documents that provide structural data for old buildings don’t exist, the site must be reverse engineered and inspected to give the structural engineer enough confidence to approve the sign structure. Occasionally, the building needs to be reinforced to accommodate a large sign.