Standing seam metal roofing offers a unique platform for mounting a variety of rooftop equipment and accessories, including snow retention, service walkways, solar modules, satellite communications, HVAC, security, and weather monitoring equipment—all without penetrating the roof.
Selecting the appropriate seam clamps for your project is a precise science rather than guesswork. The specific application for any given ancillary mounting should always consider factors such as the roof manufacturer’s approval and the service load the attachment will experience.
Seam clamps are a structural element and should be specifically designed, engineered, and tested for their failure load capacities to ensure reliable application and performance throughout the roof’s life. Factors such as metallurgical compatibility and long-term durability should also be considered to assure long-lasting performance.
The Metal Construction Association offers valuable guidance on fastener compatibility with profiled metal roof and wall panels at metalconstruction.org/index.php/online-education/fastener-compatibility-with-profiled-metal-roof-and-wall-panels (Refer to Special Note A).
What sets one clamp apart from another?
Clamps used for different purposes, such as snow guards versus solar mounting, may vary significantly in design. Snow guards need to withstand forces parallel to the slope of the roof, while those for solar mounting must handle “negative normal” loads that are perpendicular to the slope. Each clamp’s holding strength capacity must be tested accordingly and compared against specific project design loads, including considerations for seismic forces.
Testing clamp performance
Seam clamps transfer load forces into the roof panels and structure, making seam and roof panel profile-specific testing indispensable. Clamp holding strength varies depending on the seam profile, material, and gauge thickness. Therefore, each clamp should undergo certified testing for load capacity in multiple load directions on the same seam profile from the same roof manufacturer. The load-to-failure results will also vary significantly when using different materials and/or gauge thicknesses.
Therefore, it is a matrix of many possible combinations. One size may “fit” all but does not render the same holding strength. Ultimate loads must be reduced by a factor of safety when engineering the application to ensure the connection does not fail in service.
Common pitfalls
Many users and vendors focus solely on whether the clamp physically “fits” the seam. This is only a first-step requirement, and there are other criteria of greater significance such as metallurgical compatibility and certified load test results. This enables competent engineering of the attachment to do what it is supposed to do. From there, certified manufacturing ensures the product tested is the actual product shipped. Uncertified manufacturing does not.
Key recommendations
- Utilize clamps recommended by the roof manufacturer and verified through certified testing to withstand intended design loads.
- Ensure clamps are designed and engineered according to project specifications and manufactured under audited quality standards.
- Verify a product’s proven track record and warranty details to secure long-term reliability (always read the fine print).
- Limit your liability with proof of all the above from the vendor.
Rob Haddock, president of the Metal Roof Advisory Group and CEO/founder of S-5!, brings more than five decades of industry expertise to the field of metal roofing. With a background spanning contracting, roof forensics, and building envelope science, Haddock is a respected
authority in the field. S-5! has conducted more than 5,000 individual load tests on every conceivable load direction, material type, gauge thickness, and brand of roof manufacture. For more information, visit www.S-5.com.
