Self-storage construction has evolved considerably over the past decades. Since the infancy of the industry in the late 1960s and early 1970s, the use of building materials has changed, especially for exterior facades and roof systems.
Originally, exterior walls were predominantly plain concrete-masonry units (CMU) with reinforcement. Roof systems comprised bar joists, steel deck and built-up roofing. Interior partitions consisted of plywood or gypsum board on wood-stud framing. Interior doors—if any—were solid- or hollow-core wood swing doors. Exterior doors were generally overhead sectional units on tracks. These doors were very high maintenance and would limit stacking heights. Normally, there was not much concern in regard to curb appeal. In fact, there were blatant attempts to add bright and sometimes garish colors to the outside to get attention from passerby.
In the early to mid 1980s, the industry began to explode. During this period, self-storage owners and developers began looking for building materials that were more efficient and economical. The somewhat-new pre-engineered/pre-fabricated metal-building industry fit this demand. Thus, the all-metal self-storage building was born.
Today, typical interior areas of a self-storage building consist of coldrolled “Cee” columns on a 5-by-10-foot grid system with “Zee” purlins at 5 feet O.C. (on center). Local codes, roof snow loads and lateral wind loads determine the size and gauge of these components, which is why the buildings are called “pre-engineered.” The sizes, gauges, lengths, etc., are manufactured by a fabrication plant—thus the term “pre-fabricated.”
The framing materials can either be primed red or gray oxide, or can be galvanized-coated. Most full-service building suppliers and contractors offer both coatings. Roofing materials are predominantly metal and preferably standing-seam or standing rib with concealed fasteners. The gauge of roof deck is 26, 24 or 22, with 22 being the heaviest. Close to 100 percent of this type of roof material is Galvalume-coated and, on some occasions, this finish is over-coated with a long-lasting architectural color.
A condensation blanket is very popular in storage units to curb moisture from forming on the bottom of the roof deck and dripping on stored goods. This material is usually a thinner metal-building insulation (MBI) and, in most cases, is a 2-inch, vinyl-faced fiberglass blanket. If the storage building is climatized, temperature or thermal transfer control is another big consideration.
Presently, in many jurisdictions, an owner may choose the thickness of insulation he wants. Wall insulation can be 3.5-inch (R-11) or 4-inch (R-13). Roof insulation is usually 4-inch (R-13) or 6-inch (R-19). It should be noted here that many jurisdictions require minimums, such as Florida’s energy codes that require a 6-inch minimum. Many areas in northern states with harsher weather conditions require even thicker insulation, normally accomplished with two layers of fiberglass —one vinyl-faced and one unfaced. The new International Building Code, rapidly being adopted by most states, requires 6-inch R-19 with few exceptions.
Unit partitions are a form of rolled, corrugated metal sheets, either 29- or 26-gauge, and are finished with Galvalume. These metal partitions are attached to the Cee columns with tek screws. The metal partitions serve at least two purposes, providing a bigger bang for the buck. First, they divide each unit for security. Second, they serve a structural purpose. These partitions are very strong and, when attached properly, act as shear walls in the buildings to resist lateral wind loads.
Storage building exteriors come in many varieties. Due to demands by local planning and zoning boards and neighborhood committees, as well as to blend with the architectural theme of an area, the exterior look may require a mixture of two or more materials. The pre-engineered steel building can easily be adapted to receive a brick veneer or EIFS (exterior insulation and finish system), architectural CMU infill, other siding products or a combination of many. Because of stricter design criteria, other architectural materials are slowly replacing the typical metal siding that has been seen in past years.
The exteriors are also made up of steel rollup doors made expressly for the self-storage industry. Planning and zoning departments are making efforts to disallow these doors to face the main road. Instead, a decorative façade is used where required, or areas the size of doors are painted a different color to denote them.
As storage building sizes increase, more stories are added due to land costs, and more elaborate designs are created, many other building systems can be used in addition to these basic materials. There is hot-rolled steel framing with post and beam; poured in-place, reinforced concrete framing; pre-stressed concrete components and others. Any of these systems can be used with a variety of façades.
It should be noted that “typical building components” will vary in each geographical area. Coastal areas such as Florida and the Gulf Coast tend to use more reinforced CMUs, with cells poured with concrete grout to create mass and withstand up-lift caused by high winds over semi-flat roofs. In the northern tier of states, components are used to create pitched roofs to shed snow loads. In many of these varieties, cold-rolled steel interiors are used, or the ever-more-popular prefabricated, light-gauge, steel-truss system. In the future, you may not be able to say there are “basic” materials for self-storage construction, because so many varieties of materials are being used.
Heath Mulkey and Joe Trepke are part of Compass Building Systems Inc., a full-service materials supplier and contractor exclusively serving the self-storage industry in the Eastern United States. Compass is unique in that inhouse employees erect the majority of its work. A much smaller portion of the labor is performed by dedicated firm subcontractors under the company’s control. This creates a single point of responsibility for a complete self-storage building. For more information, call 800.243.8438; visit www.compassbuildingsystems.com.