Galvanised steel supports for sandwich panels: coatings, moisture and insulation continuity

Consider how the building will be used. Washdown, stored substances and high humidity may all affect the specification for channels, Z sections, sigma sections and hat sections. Specify the particular protective system and the requirements established by assessing the environment. No single coating suits every application.

Suppliers offer zinc coatings and other metallic protection systems, some of which contain aluminium and magnesium. Their designations identify different materials. A photograph cannot reliably distinguish them. Require clear material specifications for the sections, panels and fasteners.

Coating mass and steel substrate thickness are separate specifications. A thicker steel sheet does not in itself provide greater surface protection. When changing section suppliers, check both the structural specification and the protective finish, even where the section dimensions match.

Panel joints, flashings around openings and plinth connections require suitable seals. Water that penetrates the envelope may remain hidden for a long time. Detail the layers in the correct order and provide a drainage route. If a joint leaks, correct the route of entry even where the rail has a protective coating.

Keep inspection points accessible. Cold-formed sections can have recesses and contact faces that become difficult to examine once clad. Design these areas to limit standing water. A well-detailed envelope helps maintain the conditions assumed when specifying the steelwork.

A sandwich panel combines facings with an insulating core. The performance of the complete wall or roof also depends on its connections. Steel members and fasteners can conduct heat across the insulation. Trace these paths at corners, around openings and at interfaces with other building components. Core thickness alone cannot describe these junctions.

Zinc provides no thermal break. Where pads or other components reduce thermal bridging, ensure they are compatible with the structural connection. Introducing a soft layer beneath a support can alter bearing pressure, deformation and fastener behaviour. Check the thermal and mechanical requirements together.

Specify the screw, washer and any seal for the panel-to-rail connection. Match them to the substrate type and thickness, the panel properties and the exposure. Consider the service life of rail and fastener together because deterioration of either part can impair the entire connection.

Check the screw’s drilling range and connection properties as well as its length. This applies to thin hat sections and to deeper C and Z sections alike. If the section thickness changes, review the fastener as part of the approval process for the replacement material.

Follow the storage requirements for the bundled sections and panels. Avoid leaving moisture trapped between stacked steel surfaces. Condensation can occur even in dry weather. Inspect the delivery after unloading and follow the manufacturer’s storage instructions, including any limits on leaving transport wrapping in place.

Remove fabrication debris and assess coating damage before installing the cladding. Use a repair method suitable for the coating. If a member is distorted, assess its geometry separately. These checks are easier before the panels cover the connections. Later access may require removal of part of the wall or roof.

A zinc coating does not give a steel member a fire resistance rating. A panel classification also applies only within its documented scope. Check whether the specified supports and fasteners fall within the documentation for the assembly. Changing the supporting structure can affect compliance with the conditions of that design.

Galvanised Z, C, sigma and hat sections perform different functions. Describe them in a consistent specification that addresses durability, thermal insulation and fire requirements at each junction. This allows the panels and their supporting steelwork to be detailed for the building’s actual operating conditions.