Earthen floors can be beautiful and durable if done well and taken care of. They can also provide a thermal mass heat sink for a passive solar designed building if the sun shines on them, or have hydraulic heat tubes embedded in them for winter warmth.
We recommend Athena and Bill Steen’s booklet called Earthen Floors. They describe three main ways of constructing earthen floors and offer good tips for success.
Potential layers of an earthen floor, with variations:
• 1 or 2 finish floor layers, 1/2”/each, with sealant on the final layer
• Tamped dirt or cob sub-floor, 4”
• Insulation layer (slipstraw 4”-6”), rigid foam sheets (1”-2”), perlite-clay, or pumice as drainage
• Heavy plastic vapor barrier
• Drainage/waterproofing, 6”-12” of tamped gravel; or sheet of tough plastic or maybe a layer of expansive clay like bentonite
• Base of tamped earth
The ground (subfloor) should be dry before starting the earthen floor. It is essential to do TEST PATCHES in the place where the floor will be to determine what will work. There are several ways to level, and it is not necessary for the floor to be completely level. Pay attention to the floor/wall interface. The floor usually shrinks away from the wall a little. Tile or wood at the bottom of the wall protects plasters from damage from brooms, mops, shoes, etc. An earthen floor can be topped with tile, brick, or stone (especially in high traffic/wear areas). Round wood “tiles” have also been embedded in earthen floors.