Rammed-earth construction is an ancient building method that has seen a recent revival as more homeowners are interested in sustainable building materials. The process of rammed-earth construction involves compressing damp proportions of sand, gravel, and clay into a frame or mold. This compression process creates either a solid wall of earth or individual blocks. Although rammed earth has slightly less strength than concrete, it is still strong enough to use in domestic buildings. Rammed earth, like concrete, can be reinforced with rebar to help prevent failure. Materials such as wood or bamboo can also be used to strengthen the walls and maintain sustainability. Rammed earth has a very high thermal mass, allowing it to absorb heat during the day and release it at night, moderating daily temperature variations as a result. Rammed-earth construction has been met with opposition because earth construction techniques are sometimes considered substandard.