They are part of a small movement interested in "natural building" on the fringes of green architecture [The US Green Building Council doesn't even mention earthen floors in its current guidelines]. But they consider green architecture to be overly focused on energy efficiency, while they are concerned with the eco-friendliness of the entire process. The idea, according to Lloyd Kahn, a former shelter editor of the Whole Earth Catalog, is to use "materials that have as little processing as possible, like dirt, straw and bamboo."Because the floors can sometimes prove troublesome (high heels and table legs can cause cracks) a slowly growing number of "natural builders" like Bill and Athena Steen, both of whom grew up in adobe houses in the southwest, are working on making the floors "crack-free, solid, and really serviceable." (Mr. Steen's canonical guide, "Earthen Floors," is out of print, but an updated version is to be posted to the couple's Web site, Canelo Project, within a few months.)
As durable as can be, among the greatest appeals of rammed earth construction (as also evidenced by this recent Architectural Review "Emerging Architecture" nominee) is the ease of getting rid of it -- and re-sourcing it if need be. And then there are the thermal benefits. The high density and low thermal conductivity of earthen materials makes them passive solar devices, easily capturing and retaining heat during the day and releasing it at night. But as warm as earthen floors are, there's no denying their cool factor. "When people walk in, they don't say, 'Oh, nice floor,'" says one natural builder. "Everyone gets down on their hands and knees to admire it."