exterior wall material; exterior finish material
Technical term used in architecture and construction for materials applied to the outer surface of a building, such as siding, cladding, or exterior panels.
Highly durable siding is used as the exterior wall material for this house.
The choice of exterior finish material greatly affects the building's insulation performance.
内装材 is interior finishing material, contrasting with 外壁材 which is for the exterior.
Compound of 外 (outside), 壁 (wall), and 材 (material). A straightforward technical term with no obscure historical derivation.