Lumber had not been used in storage since some of the first-generation projects were built decades ago, Williams says. The demising walls on these early facilities were either drywall or plywood, leaving units vulnerable to theft. In addition, wood is combustible and can completely change the fire-protection requirements for a building plus add cost to the project.
“I am not aware of any roof structure that has near the efficiency in cost of the steel roof deck,” Williams says. “We have had owners pursue other options such as wood trusses with plywood deck and asphalt shingles, which ultimately triples the cost of the roof structure.”
Every time steel prices escalate, the option of using wood framing becomes a hot topic, says L. Bruce McCardle, vice president of Carlsbad, Calif.-based Mako Steel Inc., which erects metal storage buildings across the United States. The company considers the difference in cost between wood and steel framing, but there are other considerations to using wood. Codes, zoning, construction-type requirements and occupancy ratings prohibit the use of wood in some locales, McCardle says. Insurance for a wooden building is often cost-prohibitive. And long-term negative considerations with wood include termites, rot, moisture damage and a shorter lifespan.
For the environmentally concerned, wood is not green, McCardle says. Forests are cut down and habitats are destroyed. The overwhelming majority of steel produced in the United States comes from mini-mills that only use scrap steel for production of new materials, he adds.
The Concrete Consideration
Concrete tilt-walls are strong and can withstand considerable abuse, says Ed Heil, manager of operations and security at Lake Havasu RV & Boat Storage in Lake Havasu City, Ariz. Heil’s 207,000-square-foot facility is constructed primarily of tilt-up concrete.
Although building a concrete facility may result in a savings over metal, some unique properties of concrete affecting the final price should be considered. Construction costs may be increased due to concrete’s density. It is more difficult to drill through concrete than it is to drill through thin metal. Plus, wall perforations for lights and cameras on the exterior can add to the price of the structure. Increased construction prices can be offset by reduced maintenance costs since tenants seem less inclined to run into a concrete wall, and concrete sustains less damage.