The unique cathedral-like shape of Sprung fabric structures have graced Canadian horizons dating back to 1887 when the Sprung family first set up shop in Aldersyde, Alta.
Looking like a big boat resting on its stern with the bow pointing skyward, the characteristic Sprung shape has remained constant through five generations.
Today, Sprung fabric-covered arches have earned a reputation as being stronger and safer than equivalent sized buildings of other materials.
- In Florida, Sprung fabric shelters meet the Miami-Dade Hurricane Compliance Code.
- Bomb proof. Missiles bounce off the high tension external fabric without penetrating the surface.
- In Buras Louisiana, a Sprung tension fabric building was the only structure left standing after Hurricane Katrina in 2005.
- In the Pacific Ocean in 2015, Category Five Cyclone Pam delivered a crippling blow to the island of Vanuatu. Residents used a Sprung building as a storm shelter.
- Lake Tahoe set a world record for snowfall in February 2011, with 9.7 feet in a single week. Sprung buildings were not impacted.
- Sprung buildings in the United States missile defence system in Shemya Alaska are engineered to withstand winds of 190 km-h.
- Buildings are compatible with temperatures of -51 C to 50 C.
- The poly fabric is guaranteed for 30 years.
- The aluminum sub-structure is guaranteed for 50 years.
The Sprung tension system uses individual 15-foot wide membrane panels tensioned both vertically and horizontally with a 10-ton hydraulic jack and ram.
Membranes are a fire-resistant high-strength rip-stop fabric, installed in an aluminum frame. (see video).
In a phone interview, company vice-president Tim Sprung said each individual 15-foot section provides its own structural integrity, independent of the others. This is a major factor contributing to the overall strength of the buildings.
“We had a catastrophic failure in one of our hangers. A helicopter blade managed to slice through a beam,” said Sprung, adding that it did not bring down the building. The engineering is such that the damage only affected that one section.
“If you look at the assembly video, you’ll see that the arches are all assembled flat, then raised into position. The 15-foot wide membrane is fed in through the bottom then up and over. The trusses are on 15-foot centres. Once in place, the panel is tensioned horizontally and vertically.”
Sprung said that most of the fabric-covered buildings on the market use a single continuous tarp to cover the entire structure. That means tension is applied only from the two ends of the tarp.
Sprung structures, however, have tensioning every 15 feet, creating a high-strength surface like the drumhead of a base drum.
Military Missile proof — “In order to meet the Miami Dade criteria, the outer membrane of all our designs have to resist penetration by a missile. In a hurricane that means any sort of flying debris, sharp or blunt, large or small.
“In this hurricane business, we think of missiles as flying road signs or flying bicycles. In military zones, we’ve had ballistic missiles hit our buildings. The missiles don’t penetrate our high-tension membrane. That’s one of the things the U.S. military really likes about Sprung structures. When a missile hits the fabric, it doesn’t penetrate. It bounces off and explodes on impact outside.
“Our outside membrane is stretched very tight. That’s how it gets such strength. t almost feels like a steel panel. When you touch it, it’s like a drum. It’s PVC with a polyester scrim. The tighter we stretch it, the stronger it becomes. The horizontal tension is 1,500 psi (pounds per sq. inch). The horizontal tension isn’t quite as much.”
If the building will be heated or air conditioned, a layer of insulation is installed inside the panels, followed by a rip-stop inner high-tension membrane that is strong, but doesn’t have the UV inhibitors the outer panels have.
The interior membranes have an R-25 to R-30 energy efficiency rating, which Sprung says compares well to other types of construction.
The interior membrane provides a complete finished interior so there’s no need for additional drywall or buildout.
The interior liner also fits into the trusses on 15-foot centres.
Sprung says price per sq. foot varies a great deal because of the long list of available options. He quotes on a building only, excluding site preparation, concrete, plumbing, electrical and other basics. With those factors out of the picture, a Sprung building costs from $18 to $50 per sq. foot.