A TIMBER-FRAMED HALLWAY
Paired columns of hand-hewn redwood trees evoke
the forest primeval in this California House
by Gene DeSmidt
September, 1995 No. 97
The Bay Area rumor mill was abuzz back in the fall of 1989 about an extraordinary house nearing construction in the hills above Oakland, California. One report called it the Trilobite House because the plan resembled the fossilized remains of an ancient organism. Another rumor said the house was more accurately known as the tree house because it was designed around a curving hallway defined by a row of trees that would also carry the weight of the roof. The rumors turned out to be partly true and partly false. I got the unfiltered story- and in fact took a hand in shaping the story when I signed on as the houses builder.
The fossil story had some truth to it-- the client, a sculptor who wanted to remain anonymous, had a hillside lot with a panoramic view of the Bay Area. She wanted a house that would be both a residence and a studio, and she had some pretty definite ideas about what the house had to include. For example, she had a couple of dozen 30-ft.redwood logs, ranging in size from 16 in. to 20 in. diameters at the butt, that she personally felled on a coastal tree farm. The trees had to be displayed prominently somewhere in the house.
The client had interviewed more than a dozen architects. Then she met Warren Callister, a Bay Area architect who is in some ways more of an artist than an architect. During his career, which stretches back to the mid-1940s, Warren had practiced a brand of architecture that has found its inspiration in such diverse sources as Japanese timber framing and tugboat wheelhouses.
Warren wanted to get to know the client more before he pursued the design. He visited her at work and her warehouse studio, and he noted that she was collecting bones for an upcoming sculpture. Then he visited the site and studied the topographical map describing the contours of the hillside and the curving bench where the house would be located.
As he mulled over the possible directions that the design could take, Warren's grandson paid a visit to show off his new dinosaur book. As they paged through the book, Warren spotted a drawing of a prehistoric fishlike creature. Something clicked. Warren made a sketch of the fish on translucent paper, then he laid the drawing over the topo map. He added lines to the skeleton, fleshing out of structure bisected by a hallway lined with redwood tree posts. The posts were arranged in pairs from the front entry to a narrowing back entry, curving like the spine of the prehistoric fish. Atop the columns, a narrow gabled roof crowned the length of the house. Warren drew shed roofs on both sides of the hallway with rafters fanning out like ribs, and for the front of the house, he sketched a 50 foot diameter turn-around that resembled the fish's head. As soon as she saw the plan, the client hired Warren to design her house.
At least the foundation had two square corners-- as soon as I saw the plan, I knew we were in for a layout adventure. Like its fossil-fish inspiration, the plan curved and tapered simultaneously. The house was two ft. narrower at the rear entrance than at the front. I didn't have to study the plans very long to realize that the house had only two 90-degree angles in the entire assembly. Our only hope was to create a meticulous system for double-checking and triple checking the layouts, and to pray.
Our foundation contractor, Bob Carroll of Shelter Systems, established a master reference point 75 feet to the east of the house to pull the arc for the building's outside curve. This reference also became the point of origin for the vectors that locate the centers of the hallway posts, the rafters and the points at which the foundation changes direction. The curved foundation was formed with straight facets between each vector, giving the overall impression of a smooth curve while allowing us to build with straight lumber.
Nine pairs of tree columns created the hallway colonnade, beginning with the largest of the logs at the front door about six feet apart. Each successive pair of trees is a little smaller in diameter, and a little closer together. And under the center of each tree is a 1 in. diameters threaded rod projecting two feet above the hallway slab foundation- just another layout detail for Bob's crew to keep in mind before pouring the slab.
Timber framing the tree bents-- We turned to a company called Joinery Structures for the timber framed hallway bents. Based in Oakland, this woodworks is run by Paul Discoe, who learned timber framing as an apprentice to a temple builder in Kyoto Japan. The Japanese have had a long tradition of using timbers that are still in the round alongside milled timbers, a combination that dovetailed perfectly with the overall concept of this house. The crew started by debarking the redwood trees and then cutting vertical facets into their sides with a hand-held power planer. Then they organized the logs into pairs of equal diameters.
Because the logs descend in diameter, and because the distance between them diminish incrementally as they progressed down the hall, we were presented with an interesting question: because the hall rafters sit atop the columns, do the rafters maintain the same pitch at each bent, which would keep the ridge level but throw the rafter tails out of level, or should they change pitch to keep the tails level, which throw the pitch out of level? We chose to keep tails level because the clerestory windows were to be level, and therefore the windows would have been visually compromised if the tail line fell. The roof slope starts at 5-in-12 and ends at 7-in-12.
Seismic requirements for structural connections in houses have grown steadily more stringent over the years in California. The Loma Prieta earthquake launched another round of connector upgrades, which we had to incorporate in the framing of the log bents. Here's how we did it.
The 4x12 rafters are let into slots in the tops of the logs, where they are held fast by bolts hidden by wood plugs. Where the rafter plumb cuts abut one another, they are aligned by a spline and held together by threaded steel rod. Mortises in the rafters accept the purlins that link the bents to one another. Nearly 20 feet above the base the logs, 4x12 collar ties protrude through stepped mortises. Corresponding notches in the bottom of the collar ties nest in the mortises, and the assembly is locked together with a couple of wedges driven into each log.
Hiring Joinery Structures meant that the bents were fabricated under ideal conditions. It also meant, however, that we had to load and transport them to the site. Each bent is 26 feet tall and 13 feet wide; each one weighed about 1500 pounds. We not only needed a special 'wide load' permit from the California Highway Department, we also had to travel a predetermined route at an agreed upon time of day.
Installation day-- a stiff and persistent wind, accompanied by snow flurries, greeted us on the morning we chose to lift the bents into place. Our crane operator plucked the first bent from the truck, and as soon as the bent was hanging in space, the wind picked up. The bent began to swing ominously back and forth. It was a bad situation that endangered the crew and the ever-swelling gallery of spectators. With the clock ticking on a $300-an-hour crane, I decided to wait 30 minutes. To our relief, the wind subsided.
As the bents were lowered into place, the crew guided the base of each log onto the threaded rods that anchor the bents to the foundation. During this phase of the work, the logs were supported by nuts and washers a couple of inches above the level of the slab. This arrangement allowed us to fine-tune the height of the bents by turning the nuts. A topping slab eventually filled in the resulting gaps. We placed the nuts and washers on the tops of the rods by way of access holes in the side of the logs. After tightening the nuts, we patched the holes with square plugs of matching wood.
It took three days of crane work, accompanied by two four-man crew's working on rolling scaffolds, to complete the installation of the bents. The result was awesome: huge trees standing together again as they once were in the forest but now in a new and strange setting. We capped the hallway with roof panels made of ¾ in. inch plywood on top, 3 in. of isocyanurate foam in the center and tongue and groove red cedar paneling on the underside. As with the rest of the project, each panel was different in size and shape.
Paved to recall a streambed-- once our interior work was finished, our client put the finishing touches on the hallway floor. It is now paved with flagstones that have a luminous gold and silver surface. The gaps between them are filled with jade green pebbles. The hallway is reminiscent of a meandering stream with huge trees growing out of each side. Six months after we pulled up stakes, the fire that destroyed 3000 homes in the Berkeley and Oakland hills billowed up the slope below the tree house. I was convinced that the house had been consumed by the fire. The next morning, I went into the burn area with a police escort. As I descended the road to the house, I could see a miraculous sight. With fire still shooting up all around, the tree house stood intact. I'm sure that clearing the site of any nearby trees had a lot to do with the house escaping the fire. And maybe the finger crossing and praying helped, too.
Gene DeSmidt is a general contractor working in the San Francisco Bay area.