Dome schooling: across America, concrete domes are being used as school buildings.

Schools are all about learning, and a number of school districts are getting educated about a type of concrete building that is proving to have distinct advantages over conventional structures. These concrete buildings are known as monolithic domes, and more and more primary and secondary schools are opting for this one-piece, steel-reinforced, concrete structure known for its energy efficiency, durability, and strength.

Domed school facilities are currently under construction or were recently completed in Texas, Oklahoma, Utah, Missouri, Minnesota, and Florida. More domed schools have been built in the past 2 years than in the '70s, '80s, and first half of the '90s combined.

In 2002 alone, Italy High School in Texas and the nearby Avalon School both completed domed multipurpose facilities that are being used for everything from sporting events to graduation ceremonies. Grand Meadow School in Minnesota and Bishop Nevins Academy in Florida finished entire domed school buildings. And Centro De La Familia, a Head Start school for the children of migrant workers in Utah, also constructed a monolithic dome building.

Other popular uses for monolithic domes include churches, storage facilities, and gymnasiums. But no matter what the end use, the process used to build these round structures is unique (see sidebar) and accounts for many of the monolithic dome's characteristics.

Some schools are choosing to build their domes on 12- to 16-foot stem walls. This gives them the advantage of vertical exterior walls for window and door placement. The four new domes at Bishop Nevins Academy in Florida, for example, were built on cast-in-place, reinforced concrete about 8 inches thick. The buildings are Phase I of a project that will eventually include seven monolithic domes. "It's very unique construction, and I'm glad I went through it," says Dave Kocher of D.E. Murphy Constructors, a full-service general contracting and construction management firm that served as project manager for Bishop Nevins Academy.

The thickness of the concrete combined with reinforcing steel makes monolithic domes extremely strong: the domes meet or exceed the Federal Emergency Management Administration's (FEMA) criteria for providing "near-absolute protection ... from injury or death" resulting from disasters such as hurricanes or tornadoes. The safety features of the monolithic domes were a deciding factor for school administrators at Bishop Nevins. In Texas, schools are opening their monolithic domes for use as community tornado shelters whenever the need arises.

The same materials that account for the monolithic domes' strength also make the buildings durable. In fact, the structures are designed to last for centuries with little maintenance. But despite the buildings' longevity, they usually cost less to construct than traditional buildings of the same size. Costs for a domed commercial building are averaging $30 to $40 per square foot for the concrete shell only, depending on its height, width, and location. The Avalon multipurpose facility, for example, was estimated to cost $85 per square foot, or $1.2 million, and had a protected completion date of January 2003. The job was completed $50,000 below budget and 2 months early. Avalon School superintendent David Del Bosque, who had selected dome architecture partly for economic reasons, said he was pleasantly surprised when things went better than expected. "We are pleased to have come in under the projected budget and ahead of schedule on completing construction," said Del Bosque. "Add the savings on construction to the reduced energy bills, and the monolithic dome is just a great choice."

The energy efficiency of monolithic domes has been a major selling point for most schools. The domes are typically 50 percent less expensive to heat and cool than traditional buildings--some users have reported savings as high as 75 percent. This means that the buildings require 50 percent less heating and ventilating equipment, and therefore about a third less electrical equipment than a similarly sized conventional structure. The savings can equal the cost of the facility in less that 20 years.

If there is a drawback to the monolithic dome school, it is the building's unconventional appearance. Because domed structures are new and unusual, proponents sometimes face an uphill battle when they try to convince school board members and the community at large that a monolithic dome school makes sense. Grand Meadow School superintendent Bruce Klaehn experienced this opposition firsthand when he broached the idea of a new school consisting of five monolithic domes. Documenting the advantages by preparing a feasibility study was the key to securing both local and state funding for construction. "I don't think there was any way we could have just verbally communicated that this was good idea," said Klaehn. "Without that study, I don't think we could have had a concept of what it would look like."

In some cases, seeing is believing. The Italy Independent School District had the advantage of being located in the same town as the Italy-based Monolithic Dome Institute. But school officials still wanted to see a domed facility similar to the one that they were considering. "Of course we were all familiar with the domes; we had a good overview," says Italy superintendent Mike Clifton. "But we really had to see for ourselves. We visited Thousand Oaks--a dome already operating--and came away convinced."

In the final analysis, a school's decision to build a monolithic dome comes down to learning about the advantages these unique concrete structures have to offer. Time will tell whether monolithic domes can sustain their recent popularity over the long haul, but for now they seem like a pretty good bet to make the grade.

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RELATED ARTICLE: Building a monolithic dome.

The steps involved in building a monolithic dome are unlike those in any other type of concrete construction.

Foundation The monolithic dome gets its start as a concrete ring foundation. The process begins with the placement of a ground stake that serves as the center point and the spot to call "at grade." After the footprint is leveled in relation to this benchmark, a trench is dug around the perimeter, and rebar is placed. Half-inch plywood footer forms are then set into position.

Next come the placement of utility and communication lines and the pouring of the concrete foundation. Projecting dowels that will later be attached to the steel reinforcing of the dome itself are positioned. The number and size of the dowels depend on the size of the dome and are determined by engineering specifications. All openings in the dome, both doorways and windows, require extra dowels and additional rebar in the ring beam foundation.

A 1-inch-deep and 2- to 3-inch-wide keyway is finished into the top of the footer, dowels projecting up from its center line. The keyway surrounds the perimeter and locks the dome shell to the foundation. After the concrete has cured, the dowels are bent down to the inside of the footing, and the entire area is covered with plastic.

The Airform The attachment of the Airform is the next step. This inflatable tarp, made of single-ply roofing material, is placed on the ring base and attached with clamp straps and anchoring screws. But before work can proceed, all the large equipment and supplies that will be used to build the dome must be placed within the foundation and covered. Once everything is in place, the Airform can be unrolled and unfolded. To avoid tearing the Airform during inflation, it is important to make sure that the dowels are bent over the footing. The Airform can then be pulled down around the footing and attached.

In order to keep the air pressure inside at a constant level once inflation begins, the Airform must be attached to an air lock and air tube. A double-door airlock is used to allow entrance into the structure. To create the shape of the dome, giant blower fans inflate the Airform. The fans continue running throughout the construction of the dome.

Foam Application Before polyurethane foam is sprayed, a primer is applied over the entire inside Airform surface and left to dry for 12 to 20 hours. The primer acts as a glue for the foam, helping create a better bond with the Airform. In spraying the first layer, foam applicators start from the bottom and work their way up--it's easier to solve possible startup problems from the ground than on a scaffold. Foam is sprayed evenly to 1/2-inch thickness on the entire interior Airform surface. The foam dries to the touch in 3 to 4 seconds, but cross linking takes hours. Once the first layer is in place, an applicator can begin at the top and work down--especially on hot days. Heat generated by the foam rises, making a hotter work environment.

Rebar Hangers Steel reinforcing bars are attached to the foam using a specially engineered layout of hoops (horizontal) and vertical steel bars. Small domes require small-diameter bars with wide spacing. Large domes require larger bars with closer spacing. The first rebar hanger is attached at the top center of the dome. To secure the center top hanger, a thin layer of foam is sprayed over the hanger. If rebar hangers are not covered with enough foam, they will not be secure enough to hold the rebar. Sometimes two hangers are placed at the top in the unlikely event that one breaks.

Concrete Application The final step in building a monolithic dome is the application of shotcrete to the interior surface of the structure. Just as with the rebar, the exact amount of shotcrete is determined by engineering specifications. But typically, the shotcrete in a dome home is about 3 to 4 inches thick. Once the shotcrete has been applied, the blower fans are shut off and the monolithic dome is complete, while the shotcrete in a school is about 5 to 6 inches thick.

--Sean Lanham is a Dallas-based writer who frequently reports on the monolithic dome industry. Freda Parker contributed to this article.