The story of how zinc became a roofing material

by Ofentse Sefolo
The story of how zinc became a roofing material

Based on RHEINZINK – Applications in Architecture 4th Edition

Although the Babylonians and Assyrians knew of zinc as an alloy of brass, zinc as a metal was only introduced in the 17th and 18th centuries. According to a publication dated 1637, the Chinese were first to obtain metallic zinc by means of smelting. By 1720, zinc was produced on a fairly large scale in Wales, probably using the oriental technique. In 1743, William Champion built the first zinc smelter in England, producing about 200 tons of zinc a year.

Following the discovery in 1805 that zinc could be rolled at temperatures of 100°C to 150°C, the first rolling mills were established in Belgium and Prussia around the 1820s, using the pack-rolling method to produce sheets, usually in a standard format of 1 x 2m.

In the course of technological development, the purity of the base material reached 98,5%, yet its qualities were not nearly as high as it is today. Pack-rolled zinc could not be folded parallel to the direction in which it had been rolled and subsequently, this rolling technique and the associated technology were replaced in Germany in the mid-1960s by the RHEINZINK process and the material called RHEINZINK.

Double-standing seam
The double-standing seam roof system, a further development of the original batten seam or single-standing seam, has been around since 1899. Though also used on roofs with a steeper pitch, this system is a clear favourite for a pitch below 25 degrees.

In terms of design, the double-standing seam is characterised by sharply defined lines and numerous detail variations. This is emphasised by the increasing use of standing seam transitions, for example at hips or ridges.

The term “double-standing seam” describes a type of lengthwise connection between adjacent sections above the water level. This connection is rainproof, but it will not stop water from backing up. The edges of the sections can be formed by roll-former or by hand. The seams can be closed with a seaming machine or by hand.

Seam height
Internationally, the 25mm high double-standing seam, formed with pre-fabricated panels, has become the norm. The roll-formed machine set is available internationally and is particularly economical to use. This also applies to special roof designs such as convex, concave and conical panels.

Roof pitch
The smallest roof pitch for double-standing seams is 3 degrees, for which seam sealing measures and structured underlays should be used.

Conical sections
To install roofs with a constant pitch on buildings of rounded design, or for special details in valleys, conical sections are required. These can now be formed with profiling machines to a minimum width of 50mm. Cross seams are necessary in buildings of larger dimensions. Depending on building height and material thickness, the maximum width of the panel must be taken into account during the planning stage.

Tel: 021 671 2600
E-mail: info@rheinzink.co.za
Website: www.rheinzink.co.za

Main image: The Rheinzink double standing seam roof system installed on an upmarket residence in Higgovale, Cape Town.

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