S-5-RC Clamp

The answer to this question varies with the load direction, the seam profile, the roof material and the clamp model.

These variables result with a wide range of holding capacities from ±300 lbs (235 kg) to ±4,000 lbs (1800 kg). This is why for critical applications it is important to correctly identify the roof panel, seam type, gauge, etc along with the recommended seam clamp for the specific roof.  [ link-- Clamp-to-seam tool]  When used on some “applied cap” architectural type seam styles, S-5! may yield low load-to-failure results as compared with integrated seam profiles. Always check our load table to verify the correct allowable holding strength on your specific roof type.

When properly used, they do not. Proper use may in some cases involve exact clamp placement. The roof panel grows and shrinks dimensionally with temperature change. This movement is very minimal with shorter roof lengths, but can become significant with long roof lengths. When roof panel length is greater than 30 ft (9m), standing seam metal roofs are often designed to respond thermally with dimensional change along the length of the panels. This is accomplished at the roof panel-to-its attachment clip interface or within the attachment clip itself.

Most pre-engineered metal buildings and other clip designs utilize dual-component clips when roof panels are above a certain length. Within the dual-component clip (often called “thermal clip” or “expansion clip”), the top portion moves thermally with the roof panel, while the lower portion (fastened to structure) is stationary; the two portions are joined with a slip joint.

When attaching to this type of standing seam metal roof, the S-5! clamp can be attached anywhere along the seam whether at a clip location or between clips.

Other standing seam metal roofs rely on differential movement between roof clips and roof panels to accommodate thermal cycling. In other words, the roof panel “rides” the clip to accommodate excessive thermal cycling. When installing the S-5! clamp on this type of standing seam metal roof, the clamp locations should avoid the panel’s attachment clips if and when panel lengths exceed 30’ (9 m). Click to read more.

The key to frequency and spacing of attachment points for PV is to distribute loads to the metal standing seam panels in a manner that is consistent with the intended distribution of loads from the roof panels into the building structure.

With very few exceptions, the attachment of a single S-5! clamp (even the “Mini”) to the seam will be stronger than a single point of attachment of the seam to the building structure. Hence the “weak link” is not the S-5! clamp, but the attachment clips that hold the metal panels to the building structure, or the beam strength of the roof panel seam, itself.

The most conservative approach to the spacing/frequency of PV attachment to the roof is to determine the spacing/frequency of the roof’s attachment to the building structure; then duplicate it at minimum.

Read on for tips for determining panel attachment spacing.

Standing seam metal roofing (SSMR) is the most convenient of any roof type for mounting PV modules, either crystalline or thin-film. The seams of SSMR are beam-like elements that not only add stiffness and flexural strength to the roof panels but also provide expedient attachment points for a PV system. Joining PV modules to this roof type can be done with or without continuous mounting rails using aluminum seam clamps. Read more about how a standing seam metal roof can save you money in your next solar install.

Also, check out our project breakdown of a solar PV system using rails and using the direct-attach™ method: "5 Things to Consider When Wanting a Low-Cost Solar Module Mounting System".