wall framework; wall substrate
Refers to the structural base or framework onto which wall finishing materials (such as plaster) are applied. A technical term used in traditional Japanese construction.
土壁を塗る前に、壁下地をしっかり組む必要がある。
Before applying the mud plaster, the wall framework must be properly assembled.
Compound of 壁 (wall) and 下地 (base, groundwork). The exact historical derivation is uncertain, but the term is conventionally associated with traditional Japanese plaster wall construction.