Solar Power World recently hosted a webinar with roof-mounting experts from EcoFasten Solar, IronRidge and SunModo. The speakers shared many best practices for mounting and experiences from the field. Below are tips offered for metal roofs by Cliff Schrock, senior engineer at SunModo. View the whole webinar here, or read tips for tile roofs or asphalt shingle roofs.
1. Don’t bend roofing seam to fit a clamp. Doing so will void a roof’s warranty. Manufacturers make a wide variety of clamps for all metal roof types. Find a clamp that fits correctly.
2. Find solutions for reverse seam decks. “In my opinion, this is the worst type of roof form to deal with,” said Schrock. “And we see quite a few of these now.” Often, the valley area is too narrow for mounts, and applying mounts there would disrupt the flow of water. Mounting on the high part of this roof type requires a special mount with spacers, so tightening doesn’t crush the deck. Unirac has a mount that can work on this type of roof, Schrock said.
3. Orient rails east-west when seams run north-south. “This provides for maximum system strength on a standing seam roof,” Schrock said. “The standing seam provides strength in the N-S and the rails provide strength in the E-W directions respectively.”
4. Consider what’s below. A mounting system is only as strong as the roof below. Some metal roofs have foam insulation directly under the deck. Tightening mounts could crush the insulation. In this case, you may need a system that includes a spacer. Roll insulation under many metal roofs is already crushed at the cross beams, and further fastening is not an issue.
5. Use the right self-drilling screws. Use types that are made for self-drilling through a metal roof into wood. These screws typically have a gasket on them for waterproofing. There are special self-drilling screws for going into heavier metals, too. “Get the help of a structural engineer or the roofing manufacturer to help you find the right length screw to drill through the roof either into wood or into metal underneath so that you don’t void the roof warranty and also get the right attachment strength,” Schrock said.
