Suppliers offer endless options

Surprise Recreations structure and external lights.

Today’s buzzword in structures is flexibility. Suppliers of both air-supported and frame-supported structures are encouraging clients to think outside the box about what they want to accomplish, offering the services of company design, engineering and installation teams to realize those goals.

The blower is used to generate air movement inside the structure.

Air-supported structures, the bubbles, use internal, pressurized air to inflate and support structural fabric. The air pressure requirement is small, approximately .035 PSI, compared to a tire requirement of 35 PSI. The system design must be airtight to maintain the pressure with entrance/exit sites having either two sets of doors or a revolving door to create an air lock. Some form of cabling or netting system preserves the shape of the structure and also anchors it in place, with the type of system varying for permanent and temporary or seasonal structures.

Frame-supported structures have an inner support, generally aluminum or steel and typically including a series of trusses or arches, that is covered with fabric. Suppliers have standard framing components in stock, generally in widths ranging from 20 to 500 feet. Various options are available for the height, shape and slope of the roof. Most suppliers note the length of these structures is limited only by the size of the property.

The greenhouse for a shade-restricted area of the stadium. Crew members bring in sandbags to help secure the plastic to the bottom of the frame.

Jim Avery, vice president of Sprung Instant Structures, Inc., based in West Jordan, Utah, says, “A key feature of the frame-supported, fabric-covered structures is that they’re easily expandable.” Either end segment can be removed to insert a matching module, and then replaced to enclose the expanded building. These structures also could have a steel or brick and mortar building constructed and attached to them, or they could be attached to an existing building.

Fabric options vary widely for both systems. Some coverings are translucent to reduce or eliminate the need for daytime lighting. Multiple choices are offered in insulation, lighting, heating and cooling, and other amenities at the time of installation or as later additions.

Both systems provide clear, open space for sports activities at a faster installation time than brick and mortar buildings and at a lower cost. Brad Williams, Truss Arch specialist for ClearSpan Fabric Structures, is part of the team that concentrates on the frame-supported tension fabric buildings for the sports field market. He says, “Facilities that were considering brick and mortar structures can cover the same field area at a much lower cost.”


The Harvard Stadium bubble completely covers the FieldTurf playing surface from November until spring. Right: The removable bubble over the football field of Harvard Stadium allows for year-round use of the facility.

Air-supported structures

Most air-supported structures are year-round fixtures at their sites, used for practices whenever inclement weather occurs, as well as during the winter in cold regions or in the summer in areas where heat is oppressive. They’re equipped with sensing units to moderate temperatures to the levels selected by facility managers.

However, air-supported structures are promoted as portable, and one of the high-profile bubble installations is making a move. Following the approval of the Toronto City Council last October, BMO Stadium, home of the Toronto FC MLS team and Canada’s National Soccer Team, is converting from a synthetic surface to natural grass. The dome that covered the synthetic field is moving to nearby Lamport Stadium, as will all events for the 2010 indoor season.

These structures also offer the flexibility of short-season use, allowing a facility to give athletes both indoor and outdoor time on the same field. “The Bubble” has been providing cold weather practice facilities for Boston College student athletes since it was erected in December 1998. At 210 feet wide, 360 feet long and 70 feet high, it covers the football stadium field and extends a few feet beyond the end zones and sidelines.

It takes about four hours to inflate The Bubble. That takes place in late November. The Bubble remains inflated until spring temperatures warm around the end of March. Equipped with wind and snow sensors, as well as heating and electricity, it’s the winter practice site for varsity football, baseball, field hockey, golf, softball, and men’s and women’s lacrosse, soccer and track.

Another greater Boston area university has adopted the same strategy. A removable bubble was installed at Harvard Stadium during the 2006-2007 conversion of the football field from natural grass to FieldTurf and the addition of lighting for nighttime use. Like the bubble at Boston College, the Harvard bubble is inflated to cover the entire field as the practice facility for varsity outdoor sports from November until spring.

As air-supported structures have evolved over the years, size capabilities have also expanded. Air Structures American Technologies Inc. (ASATI), based in Rye Brook, N.Y., has designed and engineered an array of air-supported sports structures, including the Miami Dolphins’ training facility. This structure is 420 feet long, 230 feet wide and 70 feet high, enclosing 96,600 square feet of football field.

Though CEO Donato Fraioli was closely guarding any information beyond what was posted on the Web site ( ), including the exact location in Connecticut and the “high-profile sports professionals” involved in the project, a “first-of-its-kind” Sports Dome will soon be built that they purport “will dwarf” air-supported structures now in place.

The company notes it will be 400 feet wide by 670 feet long by 120 feet high and will encompass four baseball fields and four soccer fields that can be converted to a full-size lacrosse field. It will also include a clubhouse, locker rooms, classroom and a dozen one-on-one training batting cages. Another feature is to be “grandstands constructed above the clubhouse for viewing the entire sports facility and activities without obstruction.” The anticipated completion date is April 2010.


Frame-supported structures have multiple uses, from swimming pools to tennis courts, to baseball, softball, football, soccer, lacrosse, rugby and even golf.

Frame-supported systems

The basic structure design must meet building requirements. The supplier will do the preliminary research based on the location, according to Williams. “We need to know the wind, snow load and seismic code requirements to prepare a quote,” he explains. “Our engineers on staff can provide the data on the building and foundation requirements and will work with the client and any architect or consultant they designate to ensure compliance on regional or local permitting issues.”

The projected uses of the structure will guide design development beyond that. “Sports programs are always looking for extended playing time and greater versatility in their use of space,” says Jim DePaul, business director for Universal Fabric Structures, headquartered in Quakertown, Pa. “These structures can be designed with retractable wall systems and translucent roofs to become year-round, indoor-outdoor facilities.”

Optional amenities may be incorporated within the design, engineering and installation, or added at a later date. Williams says, “The facility may opt to start with the basic shell structure needed to meet requirements, using the covered space to generate additional field use and revenues. Those funds could then be used to add amenities or a second structure or expand the existing one. This build-as-you-grow plan keeps costs contained as the sports programs develop.”

The portability factor helps, too. Williams says, “These structures can be dismantled, loaded on trucks and installed at another site. The time and cost involved depends on the size and complexity of the structure. That portability can be a great advantage for those working with community or privately owned sports fields that start their programs on land that is loaned or leased to them. Banks and other lending institutions can consider the structure as a resalable unit, allowing more flexibility with financing either as an outright purchase or lease to own. Our company also offers lease-to-own options on the structure itself.”

Williams also points to the advantages of moving the structure if the facility reallocates field space or relocates to another property.


This view shows the internal framework of a ClearSpan Fabric Structure. Right: This exterior shot of a ClearSpan Fabric Structure building shows the use of both translucent fabric and opaque, colored fabric coverings.

Other structures

ClearSpan’s parent company, Engineering Services & Products Company, also encompasses FarmTek and Growers Supply. Part of the range of products those divisions provide are structures for the farm and nursery industries. Williams says, “Sports field facilities may opt for smaller structures from these divisions for other aspects of their operations, such as storage or production space. Municipalities or universities that grow their own ornamental plant materials may use our greenhouses.”

Despite all the options on the market, there are times when sports field managers develop their own structures for specialized use. A custom-designed greenhouse for the stadium field at the Surprise Recreation Campus is one of those structures, according to Joey Brazil, parks maintenance and operations superintendent for the city of Surprise, Ariz. He says, “One section of our stadium field is totally shaded during the winter months. A greenhouse, designed and constructed in-house by our mechanic and the turf crew, is assembled on-site inside the stadium to cover that area to promote germination and growth of the overseeded ryegrass. We install it in mid-December and leave it in place until February first. The frame is covered with clear plastic except for the lowest section on the side facing north. We ran out of clear plastic during the initial installation, so we used black plastic for that section. We’ve had no adverse effect, so we haven’t replaced it. We use sandbags to help secure the plastic to the bottom of the frame.”

“We set up both exterior and interior lighting to simulate sunlight and use a blower to generate air movement as necessary. The structure was designed to allow full coverage by our irrigation system.”

The author is a contributing editor for SportsField Management.