For solar installers most familiar with comp shingle or tile roofs, encountering a metal roof can be challenging. Besides just the many different types of metal, there are also different metal roofing systems. If the structure has a standing seam roof, solar installation is somewhat easier. Panel mounts clamp to the seam without penetrations. Trapezoidal and corrugated metal roofs, though, often require a direct attachment to the roofing structure. Flashing can’t be slid underneath, so waterproofing is especially important.
“The profile of a corrugated roof is not strong enough to support the mounting system, so the roof attachments are required to penetrate the roof material and attach to the structural member,” said Cody Norman, senior applications engineer with SnapNrack Solar Mounting Solutions.
To further complicate things, there are several variations of metal roofs. For example, sinusoidal corrugated roofing’s ridges and grooves are closer together, in a consistent wave-like pattern. Trapezoidal roofing has more flat space in between peaks. The type of metal roof will affect the type of solar mounting system needed for a successful install.
Each mounting manufacturer has a different design and way to attach to sinusoidal corrugated roofs.
SnapNrack’s Corrugated Straddle Block attaches to the roof at the peak of the corrugation. The fastener is positioned at the top of the ridge, out of the water channel. Still, SnapNrack suggests installers use a compatible adhesive sealant to ensure a waterproof connection.
S-5!’s CorruBracket and EcoFasten’s CorruSlide also span one ridge, but the CorruBracket attaches in the valleys, while the CorruSlide attaches more toward the bottom of the hump, not quite in the valley. (These are just a few examples. Many companies have multiple brackets or clamps with different installation techniques.)
Different still is Solar Connections’ Corrugated PowerMount which attaches at the top of two peaks. The mount’s two feet sit on two separate ridges. This two-peak attachment can be difficult because there is not a universal sinusoidal corrugation height.
“We see a lot of different heights between the ‘ribs’ of those corrugated panels, but we made our product so it could be used more as a universal option given the distance between those ribs,” said Chad Reilly, account executive for Solar Connections International.
EPDM gaskets are pre-assembled under each leg of the Corrugated PowerMount, and fasteners with EPDM washers provide a second, waterproof seal when attached through the metal roof.
Similarly, SunModo’s EZ Corrugated Metal Mount supports itself across two ridges with penetrations at the peaks of each.
For trapezoidal metal roofs, SnapNrack offers a specific solution with its Metal Roof Base. It attaches to the roofing structure in the flat surface between peaks. It is located in the flat section of the roofing panel, so an EPDM washer easily creates a weatherproof seal without requiring additional sealant.
Other companies, such as SunModo and S-5!, offer solutions that attach to the special trapezoidal ridge.
Once a metal mounting system is chosen, it’s time to jump on the roof. But that’s also not as easy as working on a comp shingle roof.
“There are some lighter gauge metals out in the market that are not as strong, so just check the roof structure before getting up on the roof to analyze and review where you’d like to layout your PV modules,” Reilly suggested. The roof’s lifetime and any corroded areas should also be gauged before putting on any extra weight.
Fall protection is also different on corrugated and trapezoidal metal roofs. With no standing seams to clamp a roof anchor, safety devices have to be direct-attached.
“The primary concern for installing on any pitched metal roof is fall protection, especially when those installers work primarily on comp shingle or tile roofs,” Norman said. “They should be using a fall protection anchor that is compatible with the roof type and does not create roof leaks once the anchor is removed.”
There may be more to think about when working on a metal roof, but a little extra attention and patience will ensure no roof type prevents the adoption of solar power.