Preparing Ring Beam — Rebar is bent over so that the Airform can be slid over the rebar and attached to the footing.
How to Attach an Airform
Handle with Care
The Airform is a highly engineered fabric structure that should be handled with great care. Many factors enter into its attachment to the concrete foundation.
Make sure the rebar is bent over the footing to avoid tearing the Airform during inflation. Place supplies or tools that cannot be taken through the Airlock within the foundation area and cover.
For single domes, the Airform is rolled up with the air lock and the air tube at bottom center. Therefore, the Airform should be placed at the location of the Airlock before proceeding to unroll it. For multi-dome Airforms, a layout diagram should be included. Proceed to unroll the Airform toward the center and unfold.
Carefully measure the circumference of the footing. Make sure the edge of the Airform is evenly spaced around the footing. Then match up the seams with the marks on the footing.
Laying it Out
The Airform should be laid out over the foundation. The entire circumference of the foundation may be covered before any clamp straps are bolted on. This is to permit any necessary adjustment of the alignment of the Airform to the foundation.
Be sure you attach the Airform on one side, then it’s opposite. Then attach the quarter points, and their opposites and continue evenly all the way around. Always match the gore points. (If you start at one place and go all the way around, you will be wrong almost every time). For domes with augments set the edges of the augments first and then fill in. The Airform will stretch to fit the foundation if you meet the individual points.
The rope in the bottom of the Airform should be pushed down three inches. The clamp straps are placed above the rope and secured by the concrete bolts and screws. Spacing of the fasteners should be 6" to 24" on center depending on pressure and type of fastener used. For small domes the spacing can be up to 24” on center. (More is generally better than less.)
For large domes the spacing should be 6” on center. Tapcon fasteners are great for domes. Also there are several other types that work well. For large domes – 150’ or larger – consider 3/8” or even 1/2” concrete anchors. The rope can be anchored with clamps, but for large domes anchors are needed through the double fabric that holds the rope in place if clamps are used.
The Airlock is then attached to the appropriate opening. If for any reason your Airform fits the foundation loosely, then it is important that you pull the slack to the center of the airlock and fold a tuck there, or at the center of a main opening, such as a double door.
Once the Airform is in place, bolted down, and inspected, it can be inflated. Inflate in as little wind as possible and as rapidly as makes sense. Inspect the perimeter as the inflation progresses. Watch for hang-ups of the Airform.
Note: We first published this article in our Summer 1998 Roundup and updated it in July 2007.
Attaching airform — Airforms can be attached a number of ways. The most common is a thin metal strap that is screwed on the outside with concrete screw anchors.
Inflator fans — After the Airform is attached, workers will attach inflator fans to the domes via air tubes that are welded in place.
Airlock — Once the air is turned on, workers will attach the air lock. The air lock serves as the entry point to the dome during the construction process. The airlock has two doors, so that while entering the dome, pressure will not be lost.
Dome is inflated. — Dual fans are used, and often dual power sources, to decrease the chance of power loss. Keeping the air pressure in a dome is the most important factor during dome construction. These fans are called SC3s
