In the right circumstances monolithic earth walls are an effective construction system, providing durable walls that mediate daily and seasonal temperature swings. Earth construction may well be the oldest method of building in the world, as ancient cities of Mesopotamia were built of rammed earth and stone. It is the quintessential local building material, with a large variety of types and styles suited to an equally large variety of climates and soil types.
We are familiar with several of these systems – including adobe, light straw-clay, cob, and hybrid adobe – but in our practice we have most frequently worked with rammed earth or the sprayed soil-cement variation known as PISE. Soil-cement is typically reinforced, and stabilized with cement or lime, important when working in locations with seismic concerns. Another option for seismically active locations is Watershed Block, a product from David Easton that uses native soils to create a standard masonry unit with natural color variations.
Without an insulating layer, monolithic earth construction should only be used in relatively mild climates and with careful attention to solar orientation, shading and passive design. The mass helps mediate diurnal temperature swings, but spaces may become too warm or cool during unseasonable periods of weather. We generally prefer to use earth as a finish on straw-bale or other insulating systems, or as a thermal mass wall within an insulating envelope. This way the full benefits of the earthen walls are enjoyed in a wider variety of climatic conditions.
Aesthetically a variety of textures and finishes can be achieved depending on technique – from the striations of a rammed earth wall, to a textured or troweled sprayed wall – giving structures a natural, timeless quality.