The popularity of metal roofing has been on the rise in recent years because of numerous benefits. It offers a 50-60 year life expectancy, is energy efficient, durable, and gives a home or building a beautiful look. But underneath those shiny panels is a substructure designed to support the roof’s overall performance.
The substructure acts as the backbone of a metal roof system, and its components work together to provide support, stability, and protection against sagging, leaks, and structural failure. In this blog, we will review substructural components, cees, zees, and custom options.
Before we can dive deep into this topic, it’s important to understand the basic definitions and purposes of various structural members.
Purlins: Purlins are horizontal structural members that run perpendicular to the roof trusses. Their primary purposes include tying the rafters or trusses together to provide structural stabilization, transferring building loads to columns, and serving as an attachment point for panels and flashings.
Eave Struts: As the name might imply, eave struts are horizontal structural members in a building located at the eave. This structural member is responsible for two primary things: transferring weight and building loads to the walls or columns; and supporting the attachment of roof panels, flashings, soffit, fascia, and gutters.
Girts: Girts are horizontal structural members that run parallel to the building walls. Much like eave struts, girts also transfer the load to other points, such as columns and footings. They also serve as a primary attachment point for panels and flashings.
Base Angles: Base angles are most often small L-shaped structural members with two legs bent to 90 degrees attached to the concrete foundation. Base angles provide support for wall panels and flashings. Beyond that, they can also be used effectively to prevent water intrusion into the building envelope.
Punching: During the manufacturing process, a series of holes can be punched in secondary substructural members. During the installation process, bolts are inserted through the holes to join two or more parts together.
Eave struts are typically punched in the flange, while cees and zees are punched in the web. Angles are not typically punched but can be if requested. Punch patterns sent in with an order will be verified against our capabilities for hole sizes and spacing.
Deep Dive into Shapes
McElroy Metal’s standard zee is an asymmetrical zee. For example: if a customer orders an 8” x 2.5” Zee, the flat portion of the top and bottom flange will be 2.125” and 2.375”, respectively.
Standard Zee and Cee shapes have many benefits; however, some applications require custom secondary substructural components. At McElroy Metal, we can produce many customized parts outside of our standard offering.
For example, we press brake up to 32’ on most of our production lines and can produce a variety of web sizes starting at 4” wide up to 24” on several of our purlin XL lines. For customer parts, flange sizes vary from 2 ½” up to 5”. Other options may be available depending on production plant and coil availability.
McElroy Metal cannot slit our purlin coil stock. Therefore, we must use a standard-width blank for all custom parts. This means that when a custom part doesn’t fall within our standard coil widths we’ll need you to supply its critical leg(s) and also tell us which legs are noncritical for the placement of excess material. For example: 8 ½” x 3” x 3” would use a 15.9375” coil to produce the desired part; however, our closest stock width is ½” wider. When placing the order, you would need to tell us if you wanted the extra ½” of material on the 8 ½” or one of the 3” legs.
NOTE: Any custom option may raise the cost of the item.