Both can either bear on top of primary-frame rafters or be framed flush. The top-bearing design is usually more economical, since it avoids expensive flange coping. Hot-rolled purlins are frequently ...

Framing anchors, framing hangers, and framing ties are used for anchoring rafters and trusses to plates ... than on top of them. Joists and purlin hangers are manufactured from light gauge galvanized ...

A metal roof typically lasts 30 to 50 years and instead of covering the whole roof with plywood, you just nail a few 2x4 “purlins” across the rafters. Screwing the big metal panels to the purlins is ...