Light Clay Walls
Light Clay describes an ancient form of building that uses the natural materials, straw and clay. It has also been called "waddle & daub" and "straw-clay". It is a thick wall system (usually 12") that is composed of loose straw coated in clay slip. These are mixed and tamped into formwork. When the forms are removed and the monolithic wall has dried, it can then be plastered with earthen plaster. The result is an all-natural, breathable wall high in R-value and thermal mass. Wood chips can be substituted for straw in this system. Light-Clay walls require a fraction of the plaster prep needed by strawbale or other wall systems.
Thermal Performance:
- Medium R-value (1.5 per inch).
- High thermal mass.
- Typical light-clay construction provides an R-20 wall.
Characteristics:
- High breathability if breathable plasters are used.
- Non-load bearing in New Mexico code.
- Light-clay accepts earthen clay based plasters without wire netting.
- Monolithic poured wall of straw and clay soil mixture (75-85% straw by volume).
Construction Techniques:
- Double 2x4 framing (12" thick) on 32" spacing is used to form & support the wall.
- The roof loads are supported by a post and beam structure or by double framed "blind studs".
- Plywood (or other) forms are required to pour the mixture of clay & straw into wall space.
- Material is lightly packed into forms by hand.
