Steel purlins and top hats, what could this industry terminology be referring to? Not to worry, every specialized industrial sector adopts its own set of proprietary terms. The steel fabrication sector isn’t any different. To find a group of purlins, just look up at the ceiling of a steel shed. There, going from one steel rafter to the next, the horizontally oriented beams are part of the structural framework.

Structurally Stabilizing Purlins 

Providing long spans of metal-supportive strength between the uppermost frame sections, the steel purlins we’re looking at are secured to those high-up structural parts. They’re long, longitudinally oriented, and made from galvanized steel. On closer inspection, each purlin has been bent at an angle, perhaps several times. There are C-shaped purlins up there, Z-shaped members, and various other roll-formed lengths of alloy-reinforced metal. Essentially, this long line of rib-like metal bars, each with its preshaped cross-sectional form, adds lateral strength to the structure. So if the familiar load-supporting triangle of a roof was formed from a group of triangular frames, it would be the longitudinal purlins that provided additional lateral rigidity.

Equipped with Top Hat Constructs 

This colourfully labelled structural member implies a certain shape, again. Viewed side-on, the horizontal length of zinc-plated steel does resemble a top hat. A length of metal plate moves outwards, then upwards at an angle, across to the opposite side of the longitudinal bar, then down and outwards again. And this profile is only conveyed to the human eye when the building support is viewed from the side, but the same could be said for a C-shaped or Z-shaped purlin. Forming more of an enclosed geometrical form, top hat supplies can be used as sheeting rails, vertical facias, and roofing frame supports. They’re just that little bit more geometrically formed, at least when compared to a purlin.

Essential Structural Features 

The steel is a workable roll-formed alloy that’s equipped with a superior weather-resistance coating. Expect a galvanized coating here, a finish that won’t corrode. Furthermore, the lateral support provided by each of these roof-crossing members must be unconditionally rigid. The purlins and top hats can’t be fabricated from an alloy that sags or deforms. Last of all, just to add detail to the vague form, the two longitudinal structural members are typically available in different thicknesses and with holes punched according to a predetermined set of building specs.

Installed and fastened as structural stabilizing beams, purlins and top hats reinforce buildings. Additional wind shearing effects bounce off of those internally armoured rooftops, as does the full force of a winter storm. Moreover, because of their structural features, buildings can assume wider dimensions and more open interior builds when these fittings are there to address such load-bearing matters.