Hat sections in façade framing: what can a secondary rail support?

One product sold as an Omega 50 illustrates why the drawing matters. Its documented depth is 55 mm and its overall width is 155 mm. The crown is 53 mm wide and the outer edges of the feet turn upwards. These dimensions belong to this particular catalogue section. Check them before substituting another hat section with a similar designation.

Hat sections can serve as battens or secondary framing for specific roof coverings and façade claddings. The outer material and applied loads determine the spacing and fixing method. For a sandwich panel, verify the detail against the chosen panel span. A light batten suitable for another covering may provide insufficient support.

Show the main rails and secondary framing separately on the drawings. Channels, Z sections or sigma sections may transfer loads over a different part of the structure from the local cladding rails. Identifying each member’s role also tells installers which members must stay in position when setting out the cladding.

For a foot fixed to steel, select the fastener for the thickness of both connected parts and its specified range of use. Timber and mineral substrates require different fixing details. Check the connection for the supporting material actually present.

Lay out the fixing points as part of the connection design. Two feet offer several possible positions, but their number alone does not determine the fastener count. The connection must transfer the forces without unintended deformation. Assess the cold-formed section together with its fixings to establish the capacity of the framing.

Set out the screws to meet the distances and bearing width specified for the connection. Check where panel joints and ends fall on the crown. At these points the required fixing and bearing area can differ from that at an intermediate support beneath continuous cladding.

A small alignment error can take up much of the available fixing width on a narrow rail. Check the rail centrelines against the panel layout before closing the façade. Matching the two setting-out plans reduces drilling corrections during installation.

Spacing the cladding away from its backing creates a cavity. To assess thermal performance, account for heat flow through the steel profiles and their fixings as well as the insulation layer. Any thermal pads or other thermal breaks specified by the design must also satisfy the mechanical requirements of the connection.

Check how moisture can escape from the façade. A ventilated cavity requires suitable inlets, outlets and junction details. The shape of the rail alone establishes neither ventilation nor drainage. Both depend on the complete wall build-up.

Existing façades and frames may deviate from old drawings. Survey the actual faces and fixing positions before fabrication. If the rails need adjustment, provide for it in the detail. Improvised packing beneath the feet can change how the connection behaves.

Assess the condition of the substrate and its ability to carry the new loads. Although the rails are light, the complete cladding adds weight and transmits wind loads. Successful use of cold-formed framing depends as much on site measurements and coordination with the cladding as it does on fabrication.

Specify section dimensions, steel thickness and grade, coating, lengths and hole positions in the order. List fasteners and additional pieces at joints separately. Protect galvanised surfaces during delivery and storage. Remove machining debris before it is concealed behind the cladding.

Choose a hat section where its two fixing planes suit the cladding detail. Elsewhere a C wall rail, a Z purlin or a sigma section may serve a different structural function. The drawing should identify the role of each member so that the secondary framing can be assessed as part of the complete façade.