Monolithic Chain Shell: A Super Protector

The Airform

For many years Monolithic has been researching and developing protection for the Airform, the exterior fabric on a Monolithic Dome. That fabric is the weakest link of the Monolithic Dome, yet it serves two absolutely vital functions.

As its name implies, the Airform forms the critical shape of the structure. That’s its primary function.

But it also has an equally vital secondary function: An Airform protects the dome’s polyurethane foam insulation from sunshine and weather. But it’s made of fabric materials that, over time, the sun can slowly degrade. So to do its job, obviously the Airform needs help.

Chain Shell

We have now developed that kind of help. We call it Chain Shell. It’s one of several coverings that can protect an Airform and help it to do its job of protecting the foam.

Chain Shell is simply another name for exterior, old-fashioned, heavy-duty stucco. It’s applied from 1.5 to 2 inches thick as an exterior finish – as it has been in many places in the world for years.

Applying Chain Shell

IMPORTANT! IMPORTANT! IMPORTANT! Begin by making sure that the dome has no leaks. It must be watertight and the final flashing details must be in place.

In general Monolithic Domes do not leak except where openings were cut into the shell for windows, doors, vents, etc. It’s very important that these are taken care of before the Chain Shell is applied.

PLEASE NOTE: Chain Shell will protect the Airform from fire, sun, hail and other serious physical damage. But it’s not a great waterproofing.

ANOTHER NOTE: The mix design for Chain Shell concrete is the same as for shotcrete. But, we have found that the only admixture that does not cause effervescent leaching from the finished Chain Shell is Berylex.

Step 1: Start the Chain Shell process by covering the dome with a moderate gauge wire layer of chain link fencing. We suggest chain link fencing because you can lay it down smoothly against the dome’s surface. It’s also galvanized, so water that penetrates through the Chain Shell won’t start rusting the chain link fencing. Although chain link fencing is not as rugged as conventional reinforcing, it’s sufficiently tough enough to use within the Chain Shell.

Step 2: Apply a layer of the concrete, embedding the chain link fencing. This layer should be about 1 to 1.25 inches thick. It’s called the scratch coat. Then wait about 3 to 5 weeks for it to cure.

Step 3: Apply a thinner layer of concrete and smooth up the dome’s surface. Wait about 4 to 5 weeks for it to cure.

Step 4: Apply the final coat of concrete. It can then be stamped with concrete stamps or designs can be drawn on the concrete – a process we affectionately call rebar art.

Rebar art means that lines are scraped into that last coat that indicate mortar lines for rock. These lines can literally be scraped through to the layer of concrete below. That makes them quite even and allows the dome’s exterior to take on the look of rock or brick or combinations there of.

After another month of curing time, a concrete exterior stain can be applied. We prefer silicone stain made by H&C concrete stain, sold by Lowes and Sherwin Williams. We have found that H&C concrete stain gives us the cleanest surface of anything else we have ever tried.

We know of no product better than Chain Shell to protect a dome’s Airform from huge hail stones, wind-driven missile impacts, fires and – heaven forbid – small-arms fire. We truly expect Chain Shell to protect the Airform and the insulating foam under it for centuries.

Maintenance for the Chain Shell should involve only a periodic washing and, if necessary, a renewing top coat to keep it looking pretty.

^{September 2011}