Passage Island Retreat

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Unlike a conventional house, a shell structure is built from the roof down. Walls are added later to seal out the weather. I know it's hard to imagine, but all the supporting formwork for the doubly curved concrete roof was built with straight lumber. (Visitors are so baffled by this idea that I've built a hyperbolic paraboloid bird feeder on my patio so I can lay a straightedge on its roof to demonstrate.) The formwork looks like quite a maze prior to the concrete pour, but once the masonry has cured, all the wooden beams and joists are removed to reveal simple, clean lines. (In fact, I used the form lumber from my house to build two other houses, one of which was a shell structure.)

Because of the blasting, the base Roy and I worked from was rough-graded, broken rock. This meant that each post supporting the formwork had to be individually cut to length. We used falsework (supports that would later be removed) to hold the 4 X 4 beams on four-foot centers until we could secure them with posts and cross bracing. The falsework also acted as a template for locating the beams. In essence, we were already working down from the top.

When we nailed 2 X 4 joists over the beams on 12inch centers, suddenly the graceful curves of the roof could be clearly seen. What had previously been a geometric abstraction was revealed in wood. The frame was then sheathed with 3/8" X 4' X 8' plywood sheets, which had to be cut in half, lengthwise, and then trimmed slightly to conform to the roof. Roy had the job of carefully fitting two-inch extruded polystyrene foam insulation over the plywood. After the rebar was placed atop the foam, we would pour 11/2 inches of concrete, which would bond to the foam.

But there was a slight delay.

On a Thursday, at quitting time, all of the insulation was in place and held down by rocks. But an overnight gale-force southeaster made short work of Roy's attempt to secure the insulation. The next morning we found that half of it had blown off the roof into the forest behind. The sheets were crushed, broken and impaled on tree branches. Only half were salvageable by trimming ragged edges and refitting the pieces to the roof. That night every spare piece of lumber was used to hold the foam down for the weekend. It wasn't until we had the 1/4-inch rebar in place the following week that we stopped worrying about losing the insulation again.

After casting the chimneys for the fireplace and barbecue-which are made of reinforcing steel and troweled cement, using a process called ferrocement and placing the prefabricated furnace chimney and plumbing vent, it was time to pour the roof. Remembering Candela's admonishment about labor costs, I took advantage of the Christmas holiday to hire a covey of high school kids. It was a calm, clear, not too cold day when we left Fisherman's Cove with a boatload of students chattering like magpies in their excitement for this unusual day's work.

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