How to Apply a Chain Shell Coating on a Monolithic Dome

Chain Shell Coated Io-20 Dome.

Exterior concrete coating, or chain shell coating, on the 20-foot conference dome.

David Collins / Monolithic Commons / CC BY-SA 4.0

In 1999, the 20-foot diameter conference dome at the Monolithic Dome Research Park got a “face-lift” by covering the exterior with fencing and coating it with shotcrete. In addition to providing a new look for the dome, a shotcrete coating will last indefinitely and provide a strong, maintenance-free exterior to your dome. We call this coating method—the Chain Shell.

First, thoroughly clean the Airform. The Airform needs to be dry to the touch before applying shotcrete. Then, attach additional molding around windows and doors. The molding serves as an extension of the existing molding and provides a depth measurement or stop-spray guideline for shotcrete being sprayed.

Cover Dome with Chain-Link Fencing.

Figure 1. Placement of the chain-link fencing on the clean dome.

David Collins / Monolithic Commons / CC BY-SA 4.0

Cover the dome with chain-link fencing (Figure 1). We recommend chain-link fencing because it molds to the dome shape better than chicken wire and provides non-structural reinforcement to the shotcrete coating.

Connect Chain-Link Sections Together.

Figure 2. The chain-link can be connected using hog rings, cable ties, or tie wire.

David Collins / Monolithic Commons / CC BY-SA 4.0

Connect the pieces of chain-link by using hog rings, cable ties, or tie wire (Figure 2).

Protect Openings.

Figure 3. Protect openings and other accessories with plastic.

David Collins / Monolithic Commons / CC BY-SA 4.0

Mask windows, doors, openings, air conditioners, etc., with plastic to protect from overspray (Figure 3).

Initial Shotcrete Application.

Figure 4. Apply an initial ½ inch of shotcrete over dome.

David Collins / Monolithic Commons / CC BY-SA 4.0

Spray the shotcrete. Initially, a ½-inch cover coat should be applied (Figure 4).

After the cover coat is set, spray enough shotcrete to cover the chain-link fencing, approximately 1 ½ to 2 inches total thickness.

Embed Chain-Link Fence with Multiple Passes.

Figure 5. Allow adequate curing time between shotcrete applications.

David Collins / Monolithic Commons / CC BY-SA 4.0

Curing time is dependent upon weather conditions. Allow adequate time between shotcrete applications (Figure 5).

Cover Chain-Link Fencing Completely.

Figure 6. Approximately 1 ½ to 2 inches of shotcrete will be applied to completely cover the fencing.

David Collins / Monolithic Commons / CC BY-SA 4.0

On an average day, we spray one coat per day on a large dome. By beginning early in the morning, you should be able to spray a second coat on a small dome by late afternoon (Figure 6).

When the chain-link is completely covered with shotcrete, clean up the overspray by trimming, molding, shaping and shaving the shotcrete.

Spray Final Coat.

Figure 7. Spray the final coat. A powdered colorant may be added to the final mix to provide color.

David Collins / Monolithic Commons / CC BY-SA 4.0

To add color to the final coat, a powdered colorant can be added to the shotcrete mix. Spray the final coat (Figure 7).

Roll on Concrete Stain or Paint.

Figure 8. A concrete stain with a sealant can be applied when the final coat of shotcrete is cured.

David Collins / Monolithic Commons / CC BY-SA 4.0

When the exterior is completely set, the shotcrete can be left as sprayed, but a clear concrete sealant must be applied. A concrete stain with a sealant or exterior paint can be rolled onto the cured finish (Figure 8).

It is vital to clean your concrete pump after each use and perform necessary maintenance according to the owner’s manual when the job is complete.


Reprinted from the Winter 1999 issue of the Roundup: Journal of the Monolithic Dome Institute