Architects: Paul F. Hirzel
Location: Juliaetta, ID, USA
Area: 5450.0 sqm
Project Year: 2013
Photographs: Jim Van Gundy, Robert Hutchison
From the architect. At the end of a single lane road cut into a hillside, on a dry west-facing slope near Juliaetta, Idaho, the owners wanted to restore a pioneer vineyard (the first known vineyard in the canyon). Preserving the most ideal land for the vineyard, we located two structures – one above a flood plain, the other perched on a narrow basalt cliff overlooking a spawning pool on the Potlatch River. The owner and guest quarters are housed in one structure and the other is used for special events such as wine tasting.
The site presented a number of challenges: summer temperatures that can reach 110+degrees F, a healthy population of rattlesnakes and bull snakes, periodic river flooding (the flood plain site flooded twice during construction), and limited access for construction equipment. In addition to these environmental conditions, the clients requested to be as close to the river as possible for its cooling effects, sounds, and visual pleasures. A strong energy conservation agenda was also an important requirement.
The building forms were derived from these circumstances.
The main structure (living-guest quarters) is set on four 8-inch thick concrete piers. The central pier is doubled to make space for mechanical/electrical systems that connect lateral runs to the rooms. The finish floor elevation of the bridge structure (905 feet above sea level) was determined by a water shed hydrology analysis and is set above the 300-500 year flood event elevation. This ground separation also discourages snake infestations. A 15-foot deep steel Howe truss system spans 80 feet at the center span with 32/16 foot balancing cantilevers at each end. The longer cantilever extends out over the river while the other continues to a gangway that leads to the parking area. The location of the structure is intended to weave the bridge and ramp into an existing grove of cottonwood trees. The three main parts of the conditioned floor area, the owner wing, guest wing, and a shared wing with kitchen, dining, and lounge space, are essentially separate buildings that have their own heating/cooling systems. They are super insulated on all sides and independent of the steel bridge structure and are therefore referred to as “three refrigerators setting on a bridge”. Connecting these three parts is an unconditioned screened and glazed corridor and porch that can be opened up as needed for manual temperature and ventilation control.
The steel bridge truss supports a wood lattice (128’x24’) that shades conditioned space below and reduces cooling loads by 20%. A secondary benefit is an accessible roof deck for easy roof maintenance and mischievous wine tasting, as it has no guardrails. Single lane road access into the site required sizing the prefabricated truss members to be transported on a short flatbed trailer and installed with a small boom crane.
The second structure (event space) is roughly 1000 feet up river from the main structure. The small building is constructed with a steel exoskeleton to cantilever 40 feet over the river. This was required to meet the river setback requirements stating that foundation walls could not be within 100 feet of the center of the river. The cantilever also provided a platform for viewing a rare Steelhead spawning pool below. An existing road/trail that runs along the riverbank also needed to be accommodated so you can drive through the structure on your way up river.
All connections for both structures were bolted with no site welding to reduce fire danger. As a result the home can be disassembled and removed from the site with only the concrete piers remaining.
Interiors of the structures are tough and utilitarian, clear finished local pine, exposed framing lumber, with standard plywood sheathing. The event space uses sealed OSB flooring. Exterior finishes are galvalume metal siding, galvanized steel, and oiled garapa wood decking.
Because both structures have essentially “scaffolding” as a part of their design, construction costs were kept to a minimum at $118 per square foot for the main structure and $147 per square foot for the event space.