Coating a 74-Foot Dome: The CalPortland Silicone Project in Portland OR

Not every coating project involves a flat commercial roof. In Portland, Oregon, building materials company CalPortland needed to protect an inflatable dome used to store concrete pre-mix powder, a structure standing 74 feet high. The dome’s Hypalon membrane had been coated before with an unknown product, and the owner wanted a cost-effective, environmentally responsible way to renew the envelope without tearing the structure down.

The Challenge

The dome’s shape ruled out conventional roofing entirely; only a fluid-applied system could conform to its continuous curve. Access was the other major hurdle. Crews needed to reach every point on a tall, rounded surface, which meant working from telescoping lifts reaching 65 to 85 feet and rappelling down the upper sections. Any replacement scenario would have required demolishing and rebuilding the dome, a far more expensive and disruptive outcome.

The Coating Solution

Applicator Long Painting selected GacoFlex S4222 silicone in gray, chosen in part to match the structure’s existing finish. The coating was applied by power roller fed by a Graco King 60 pump, with two coats installed at 20 wet mils each. At the base of the dome, GacoPatch silicone sealant was used to terminate the coating at the bottom edge, sealing the transition. The silicone bonded well to the previously coated Hypalon surface, confirming the system choice.

The Results

The project gave CalPortland a renewed, weatherproof envelope over its storage dome at a fraction of the cost of demolition and reconstruction. The finished gray silicone surface matched the original aesthetic, added graffiti resistance, and demonstrated how far fluid-applied technology can stretch beyond conventional roof geometry when access planning and product selection are handled carefully.

Project photos