For centuries, the Dutch have shown great ingenuity in keeping the water that surrounds their low-lying country at bay. That's allowed them to preserve land on which to build housing for the dense population of the Randstad, the crescent that runs from Amsterdam to Rotterdam. Dutch architect Herman Hertzberger has turned the idea on its head by putting houses in the water. Of course, there have always been houseboats in Holland. The architect says traditional Dutch houseboats were his inspiration, but notes that as places to live these quaint, colorful anachronisms look better than they work. They're uncomfortable—too much boat and not enough house, he says.

Hertzberger's Amsterdam-based Architectuurstudio designed its first “watervilla” back in 1986. It floated on foam-filled concrete—not exactly a traditional material. Since then, the studio changed the floating foundations from foam-filled concrete to buoyant steel tubes, inspired by off-shore oil rigs. “It was necessary to change the structural system because we wanted the house to float freely in the water and be able to change orientation,” explains project architect Patrick Franzen. The design also nearly doubled in size from 80 square meters to 156 square meters, or about 1,680 square feet. (The updated model can be expanded up to 200 square meters, while the original design was fixed.) Most important, the firm was able to build a prototype of the revised house in De Veersche Poort, located in Middelburg in southwestern Holland, which will eventually be home to six Watervillas. The developer of De Veersche Poort commissioned the prototype's construction.

Like oil rigs, the Watervilla floats on a hexagonal frame of six 10-millimeter-thick hollow steel tubes roughly 2 meters in diameter. The D-shaped pipes create enough buoyancy to support 135 tons and are engineered to keep the aquatic houses stable even in choppy waters or high winds. The floating base supports a three-story steel structural frame with steel-plate and concrete floors. The cladding is a prefabricated, low-maintenance skin of made of lightweight steel plates over the 60-centimeter-deep steel frame with foam insulation. The interior can be finished in a number of materials; Hertzberger's studio clad the interior walls in 18 centimeter-thick plywood. Prefab materials allow the house to be built on a quick four-month construction schedule.

The first floor of the prototype currently bobbing in the waters of De Veersche Poort contains two bedrooms, a bathroom, and storage space. Upstairs, via a spiral staircase, is the open living/dining room and a kitchen, all surrounded by walls of floor-to-ceiling glass. On the third level is a large open space that can be used as an office or spare bedroom. Each level has outdoor terraces. An 8-meter-long gangway provides access from shore.

The prototype includes standard (for Holland) heating and cooling systems, but future options include underfloor or wall systems; photovoltaics are another energy-saving possibility, although Franzen explains that the Middelburg villa doesn't have many high-tech bells and whistles in order to keep
costs down.

Obviously, it's possible to navigate the Watervilla to a number of different locations, as much for a change of scenery as for energy conservation: Hertzberger designed the villa to rotate 90 degrees by means of two steering wheels. The Watervilla can be moved to capture the best solar orientation, facing the warming sun in winter and away from the sun in summer to minimize heat gain. Franzen says he would recommend a small onboard motor if the owner wanted to change the home's position weekly or even daily.

So far, Watervilla is an information center—consider it a floating "model home"—but Franzen anticipates occupancy by the beginning of 2004. Franzen says the studio can't calculate the exact building cost, given the high engineering expense involved in getting a prototype off the ground (or into the water), but he anticipates that the flotation system will be costlier than earthbound foundations. He estimates future houses will cost between 2,000 and 2,500 euros per square meter—currently $218 to $273 per square foot.