Outdoor sign is often judged by its durability, but the durability of any sign is constantly being tested by weather conditions, vandals and the damaging effects of the sun.

The most common of outdoor signs are comprised of metal with flat screen printing. They are generally made from aluminum or "bonderized" steel (a type of finish put on steel to prevent weathering and corrosion) and have a life span of about 10 to 15 years. They tolerate weather, fading, oxidation and rock chips without noticeable damage.

Most traffic signs are made from 18-gauge steel with flat or reflective screen printing. The trend, however, is toward lighter-weight, rust-resistant aluminum, even though it's more expensive.

Another durable material for outside sign design is fiberglass, which has little scrap value and is, therefore, a good choice for vandalism-prone locations. It's extremely light, easily cut and won't chip.

Signs made from recycled plastic are lightweight and can withstand three to seven years of outdoor exposure. Many people in warm climates use them because they can withstand harsh conditions such as heat and hurricanes.

There are also special exterior vinyl signs that have a two- to seven-year life span. Pressure-sensitive (stick-on) vinyl signs -- though inexpensive -- can peel or fade in harsh weather and sunlight, and may not be available in large sizes.

Reflective Materials

Many outdoor signs -- especially screened metal traffic signs -- are reflective for better visibility. Sign manufacturers generally use a vinyl, reflective-laminate sheeting to create reflectivity, which also gives signs a longer life span by making them more resistant to ultraviolet (UV) rays.

Another method used to create reflectivity on embossed signs is to attach small glass beads to the face of the sign to reflect light. This method is not preferable anymore because the beads can fall off or be removed by vandals. Reflective signs are slightly more expensive than non-reflective, about 10 to 15 cents per character for glass beading.

Embedded fiberglass signs have built-in UV inhibitors. There are also some lacquer-like coatings with UV inhibitors which may be applied over painted or screened signs, though some companies don't like to use them because they give signs a yellow cast. Coatings run about $2 to $3 extra per sign.

Signs can also be coated with a product called Tedlarreg., a vinyl-type sheeting which provides UV protection and makes signs durable and resistance to graffiti. Tedlar coating has a three- to five-year life span and increases sign cost by about 25 percent. It is generally used on plastic signs, though it can be placed over any type sign.

Graffiti Removal

There is also a clear graffiti-proof coating that can be applies to signs to keep indelible markers or paints from seeping into the sign. These coatings may cost an extra $1 per sign.

Another graffiti deterrent is overlay film, cut to size and applied before the sign is installed. If the sign is vandalized, the film simply peels off, taking the graffiti with it. A 12-inch by 18-inch sheet costs $6 to $7, but a disadvantage is that it's tricky to apply (or reapply) because your crew will need a completely flat surface and dust-free environment for proper application. Graffiti remover sprays and solvents that won't damage signs are available for $15 to $20 and will clean about 100 signs.

Sign prices are generally figured by the square-inch cost of the material, fabrication times and typesetting charges. Typesetting cost depends on letter size. Engraved letters up to one inch tall cost approximately 15 cents each. Raised letters -- for signs which meet codes outlined in the Americans with Disabilities Act (ADA) -- cost about 50 cents each for each one-inch letter.

A 24-by-24-inch aluminum reflective sign costs about $76; a fiberglass sign flat-screen printed sign of the same size is about $38. Pressure-sensitive vinyl signs are economical -- $10 to $15 less than aluminum. An aluminum sign with reflective coating is the most expensive to produce, followed by reflective steel, flat-screened steel and fiberglass. Plastic signs are usually the least expensive.

Sign maintenance includes using soap (such as dishwashing liquid) and water -- avoid abrasive cleaning methods, especially on screen-printing or vinyl. Fiberglass signs will clean up with regular soap and water or other chemical cleaners, but the chemicals in these solutions may eat into the finish on vinyl or screen-printed signs.