History of Standing Seam Roofing

A standing seam joins two metal sheets by turning up their edges and folding them together into a raised, watertight rib that sits above the drainage plane. The technique is far older than the modern roll-formed steel panel and has its roots in traditional European sheet-metal roofing.

Hand-folded metal roofs

Metal roofs of copper, lead and later zinc and terne-coated iron were laid as relatively small sheets or "pans", joined by folded seams or by wrapping the metal over wooden battens or rolls. Raised and folded joints allowed each sheet to expand and contract with temperature while keeping water out, and put the joints above the flow of water. Early dated examples of large metal roofs include the copper roof of Hildesheim Cathedral (1280) and Kronborg Castle (1585), and the lead roofs of medieval cathedrals and halls such as Westminster Hall.

The 19th century

Cheap iron transformed metal roofing in the early 19th century. Iron sheet dipped in molten tin or zinc resisted rust, and terne plate, iron coated with a lead-tin alloy, became popular for roofs because it was cheaper than tinplate and more durable outdoors. In Paris, rolled zinc became the standard covering for the upper slopes of Second Empire mansard roofs, laid by specialist roofers using folded and batten seams.

Industrial production

In the 20th century, continuous rolled steel coil, metallic coatings and factory paint finishes allowed long panels to be formed by machine, either in a factory or with portable roll-formers on site. Concealed clip fixings, which hold the panel without piercing it, allow panels to move with temperature. Panels could now run the full length of a roof slope rather than being joined in short pans.

Continuity

Despite industrial production, the basic profile of a folded double-lock seam remains recognisably the same as that formed by hand on copper and zinc roofs, and hand-seaming remains a core heritage skill in Europe.