Understanding Seam Clamp Testing

by Jonathan McGaha | 30 April 2016 12:00 am

The importance of standing seam clamp testing methods

As the metal roofing industry works to grab a larger share of the roofing market, for both re-roofing and new construction, so grows the idea of attaching ancillary items to standing seam metal roofing systems. Everything from snow retention systems to solar panels are being connected to seams. Installers should be selective about the metal roofing systems they install. They should learn as much as possible about the quality of the substrate, the coating and the panel anchorage, as well as the warranties offered by the manufacturer. Metal roofing manufacturers invest in third-party testing of their systems, tests for wind uplift, wind-driven rain, water and air infiltration, debris, impact resistance and even fire resistance.

Similar cautions should be observed when selecting a seam clamp to attach any ancillary item on a standing seam metal roofing system. It should be serviceable for the life of the roof. That may not sound like a big deal, but consider the different number of panel profiles and seam styles available on the market today. Then consider how many manufacturers are offering those goods, because every profile produced by one manufacturer is a little different compared to that same profile produced by another manufacturer when it comes to the exact seam geometry.

 

Testing Importance

That’s why testing becomes so expensive. There are about 20 different snap-lock profiles being manufactured and as many trapezoidal standing seams, and a growing list of “T” seams, bulb seams and nail flange profiles. Many are offered in multiple gauges and materials (steel, aluminum, zinc, copper, stainless).

Here at S-5!, Colorado Springs, Colo., we have spent the money to test our seam clamps for holding strength on every standing seam system in the industry in order to host load-critical ancillary items. In fact, we test each roofing profile three times, averaging the results. Any variance in the foregoing variables will affect the holding strength. We test seam clamps in two different load directions with setscrew tension installed to 115 inch pounds, but publish and instruct an installation tolerance of 130 to 150 inch pounds to ensure the minimum tested tension is, in fact, reached. Then we use a minimum safety factor of 2.0. This enables the safe and prudent design of any ancillary attachment to distribute specific forces of nature into the metal panels and structure with confidence that it will perform without risk in service.

We also provide web-based tools to enable the users of our systems to properly design roof accessory applications so they will perform for the life of the roof without failure. Absent the panel-specific testing, there is simply no way to quantify holding strength and design such an engineered application. A good example is snow retention. Snow on a roof presents specific loads on the snow retention system. These loads can be easily calculated, and with proper testing the snow retention system can be designed to resist them successfully. Currently there are no ASTM or UL tests for the holding strength of seam clamps and any possibility of standardized testing is still years away. For that reason we invented a protocol for appropriate testing and have performed thousands of tests in a thirdparty A2LA accredited lab over the last 23 years.

 

Clamp Characteristics

Seam clamps are manufactured with different screw points where they engage the standing seam. Availabilities include common cup point setscrews and the highly recommended oval (or round) point setscrews.

A cup point setscrew features a concave indentation on the screw tip. This screw is mainly used in applications where the cutting in of the cup point end of the screw is desirable, such as securing a pulley to a shaft. Oval point setscrews feature a rounded point on the screw tip. This setscrew is used in an environment where minimal deformation or damage to the substrate is required.

The Metal Building Manufacturers Association (MBMA) writes in its Metal Roofing Systems Design Manual, “Any attendant setscrews that secure the clamp to the seam should have a rounded point (not a cup point) so that gouging or breaching of the metallic coating is avoided.”

In addition, the Metal Construction Association (MCA) reports in Metal Roof Design for Cold Climates, “Some mechanical attachment products utilize ‘cup point’ set screws that may tear the seam material under load or damage panel coatings leading to premature corrosion. Other clamping products use round tipped setscrews to avoid this panel damage. Some use only one set screw, others use several. Again, appropriateness and completeness of lab testing should be scrutinized as well as the specific details of attachment before a final system choice is made.”

Rob Haddock is president/CEO of S-5!, Colorado Springs, Colo. To learn more, visit www.s-5.com[1].

Source URL: https://www.metalconstructionnews.com/articles/understanding-seam-clamp-testing/

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