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.
We perform hundreds of rigorous tensile load tests parallel and normal to the panel seam on various gauges and profiles, the results are tabulated for your convenience here: Load Test Results.
In the parallel load direction, loads that are introduced into the clamp will transfer to the panel’s seam and accumulate to the point of fixity in tension (or compression). Roof panels must be adequately attached to resist these loads. S-5! clamps have been laboratory-tested on various seam types, profiles, and materials for ultimate failure loads parallel to panel seam (“drag” type loads). The ultimate load-to-failure results vary with individual panel profiles and gauges. Watch this video to understand more about testing and why we test. [insert ways we test video].
In the negative normal load direction, with 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. The “weak link” then 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. Ultimate loads normal to the panel seam (both positive and negative) are more a function of the panel’s beam strength and the failure strength of the panel’s attachment clips than of the holding strength of the S-5! clamp on the panel seam. These values will also change with various attachment spacing.
ASTM standard E-1514-93 for structural standing seam metal roofing requires that roof panels by design must withstand a minimum 200-pound point load in positive (downward) pressure at the panel’s weakest point (the flat of the panel at midspan). The Army Corps of Engineers Technical Instructions for metal roof design spec (TI 809-29) says that the same value should be 300 pounds.
Almost any structural metal panel system will meet and easily exceed the above specifications. The seam area is also much stronger than the panel flat. S-5 attachments transfer positive loads into the panel seam. HVAC units, for example, are mounted successfully in this fashion on numerous projects, utilizing four, six, or eight clamps (bearing points) for a single unit of considerable weight, by distributing the weight of the unit equally over those bearing points so as to maintain a maximum point load within ASTM or ACOE limitations. The building structure must also be designed to support these loads.