下した葺ぶき

noun

built-up roofing; under-roofing

Technical term in construction for a roofing method where multiple layers are built up, or for the underlayer of a roof.

• 下した葺ぶきにはアスファルトルーフィングがよく使つかわれる。

  Asphalt roofing felt is often used for built-up roofing.