mixed materials
A roof-supporting framework combining different materials, each forming a significant part of the roof structure.
A mixed material roof frame is an underlying support framework for a roof built from a combination of multiple different materials, each forming a significant part of the roof structure.
Several materials must contribute significantly to the support structure. A minor accessory of another material does not by itself establish the mixed-material form.
The combination concerns the frame. A frame of one material beneath a covering of another is not mixed merely because those separate roof parts differ.
