Roofing element for greater span lengths - has I=beam spacers between thicker wood upper and thinner metal lower skins

摘要

Roofing element comprises two flat outer skins interconnected by spacers. The upper skin is thicker nonmetallic material and the lower is of thinner metal sheet, for taking up compression in the upper and tension in the lower, skin. The spacers are parallel composite beams glued or cemented to the skins, opt. together with nailing. The beams are at least largely non-metallic and have wider flanges and interconnecting thin webs. Polyurethane insulation is pref. injected between the outermost beams of adjoining elements, or insulation is provided by fibrous strips. The upper skin is pref. of plywood and the beams are I-beams with a web of wood-fibre board and wood flanges.