S-5-KL7™ 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.  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. 

Read more.

Our standard test procedures are to test the mini (one setscrew) clamps with negative load normal to seam, and standard (two setscrew) clamps with load parallel to seam. We have performed numerous parallel to seam datum tests on mini clamps and concluded from engineering analysis the mini clamp is (conservatively) obtaining more than ½ the strength of the standard clamps. In fact, the majority of the datum testing indicates the strength of a mini is closer to 2/3 the strength of a standard clamp. In due course, we are adding certified lab testing in this load direction for mini clamps.

In the interim, should certification of the load application parallel to seam be critical to your application, we suggest using the standard (two setscrew) design.     

View Load Test Results with Load Pulling Normal to Seam

View Load Test Results with Load Pulling Parallel to Seam

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 more about how to determine panel attachment spacing. 

The setscrews, which make a small dimple in the panel seam, optimizing holding strength, are normally tensioned to 115 inch-pounds for test purposes. This is because the tools normal to the trade are rated at this tightening torque. But there are some exceptions to this rule. On some profiles and gauges in steel, screw tension of 115 inch-pounds will not adequately dimple the panel seam. For this reason, some tests are run with higher screw tensions on profiles with increased gauge or thickness.

The appropriate setscrew tension is always published on installation instructions for every clamp. When the tested torque is 115 in. lbs. the recommended installation torque instructs a window between 130 to 150 in. lbs. to be sure the tested torque is reached. When test torque is higher, the corresponding window is also higher.