Magazine article Sunset

Mud-Building 1990s-Style: The Rammed Earth Idea

Magazine article Sunset

Mud-Building 1990s-Style: The Rammed Earth Idea

Article excerpt

Mud-building 1990s-style: the rammed earth idea

Plastered walls and tree-size beams give this three-story hillside house in northern California's wine country a timeless look. Its basic construction relies on earth building, a centuries-old technology that has taken an evolutionary step forward with the addition of cement, pneumatic tools, and knock-down plywood forms. The densely compacted walls are termite-, fire-, and rotproof, and far outlast those of conventionally built houses. Practiced by the Romans as well as by the ancient Chinese, earth building found its way into this country in the late 1800s. Traditionally, the method mixes soil from the building site with water and compacts it between wooden forms to make thick walls--like those in an adobe, but without individual bricks. In modern earth building, also called rammed earth construction, cement is added to clean mineral soil (free of humus) and a small amount of sand. Pneumatic tampers compact the mixture in knock-down forms to create 18-inch-thick wall panels. In a system developed by David Easton of Rammed Earth Works, the panels are then incorporated into a concrete post-and-beam frame. Each panel is built independently of the others. At their bases, the panels rest on and tie into a concrete perimeter footing; along their sides, they have vertical slots (or "keys") left after the forms have been removed. The 8- to 10-inch-wide spaces left between adjacent panels are infilled with steel-reinforced concrete; these become the posts of the post-and-beam system. It's this system that does all the real structural work. When the concrete is poured, it fills the keys and locks all the panels together. Next, poured-in-place concrete "beams" are formed to cap the panels and posts and span openings for windows and doors.

A dramatic house in harmony with its surroundings

By using soil from the site and relatively little wood for framing, this house conserves natural resources and is free of pollutants. This method is labor-intensive, so the house cost about 20 percent more than a traditional structure to build. But it offers great potential for energy savings. The house's mass and orientation to the sun make it solar efficient. Its thick walls and slab floor absorb heat and cool the rooms on hot summer days; at night, they release the stored heat into the air. On winter days, the house's thermal mass receives heat from sunlight entering the south-facing windows (and from fires in the several fireplaces) and radiates it back into the air at night. …

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