Archiwa Sheet metal flashings

Thermal movement and joints in long parapet copings

A long parapet cover changes dimensions with temperature. As it heats up, the steel expands; as it cools, it contracts. The detail should account for this process in how sections are divided and fixed. Choosing an attractive coating is not enough. The substrate, shape and connections must also be addressed. The flashing can then perform its function without unintentionally stressing the entire strip. Thermal expansion is a property of the material. With a small element the change may be slight, but over a long run it becomes more noticeable. As a guide, a steel element three metres long can change length by about 1.8 millimetres with a temperature change of fifty degrees.

Bending prepainted sheet without spoiling the shape or finish of the flashing

Non-standard flashings are made from flat sheet, but once bent they must satisfy several requirements at the same time. They must fit the building, keep the correct surface, and be installable. Matching leg lengths alone is not enough. The material, the actual shape of the corners and the bending sequence all matter. It is worth agreeing these points before production, especially when the flashing will be visible along a long stretch of façade. Coated sheets are not a single variant with identical forming capabilities. The type of substrate, the thickness and the arrangement of the protective layers all matter. The shape should match the properties of the specific sheet. The material should not be changed arbitrarily once a demanding cross-section has been approved.