In the second part of the EcoFasten guide to best practice tips for solar mounting installation, “Keeping it Lean in 2019,” we focus on the roof itself. From shingle to low-slope membrane, every roof presents its own considerations and challenges for installers when it comes to roof attachment components and mounting systems.
Selecting the right solution for the right roof is vital to installing a reliable, high-quality system that meets your customer’s expectations and ensures the integrity of the roof. The content below dives into the different roof types installers face and the steps that should be taken for each type when deciding on mounting systems and attachments.
Roof Types and Materials Matter
With all the different types, shapes and orientations of roofs, not to mention the various roofing materials, the choice of roof attachment components and mounting systems depends on many factors. While there is no “one size fits all” for solar mounting, here are some lean best practices to follow when installing on specific roof types that will ensure the integrity of the roof:
- Composition shingle. Make sure to notch the flashing to fit around nails to ensure code compliance by allowing the flashing to extend up and under the third course of shingles. The flashing should also be positioned between the vertical joints of shingles for additional waterproofing measures.
- Tile. It’s important to keep your time on the roof to a minimum. Even the strongest tiles can be brittle and break easily. Be especially careful not to drop tools while on a tile roof. Replace all cracked or damaged tiles prior to installing. Mission (clay) tiles are fragile, so it’s not ideal to install over clay tiles because of excessive risk of breakage. The “strip and go” method is often used, where the tiles are removed from the section of the roof that the array will be installed on and replaced with asphalt shingles. Solar mounting solutions that replace a tile with flashing are also a great source for replacement tiles. Make sure the flashing meets UL 441 and ICC-ES AC 286 standards and specifications.
- Slate. The slate roof installation process is very similar to a composition shingle install, but the slate tiles will need to be removed prior to installing. Whatever you do, do not drill through slate. For code compliance and waterproofing properties to remain intact on slate roofs, make sure the top edge of the flashing extends up and under the third course of slate.
- Metal. For installations on metal standing seam roofing, make sure to choose roof mounts that employ clamp-to-seam technology, which will never penetrate the roofing materials due to the use of set screws. Also make sure the mounts used will not void the roofing manufacturer’s warranties. When installing on corrugated metal, it’s important to use a mount that either attaches to the ribs of the panel (as opposed to in the channel, where water flows and moisture accumulates) or to use mounts that employ waterproofing technologies such as EPDM rubber bushings that form a compression-fit once the fastener is attached. One of the advantages of installing a solar array to a metal roof is that metal offers one of the longest lasting materials on the roofing market, so there’s only a slim chance you’ll need to re-roof before installing the PV system.
- Low-Slope/Membrane. It goes without saying, but we’ll say it anyway: the roof must remain watertight. In most low-slope roofing, this is achieved by flashing the attachment points. Different low-slope roof coverings and membranes will have different flashing requirements. For example, TPO, PVC, EPDM and other single-ply membranes use thermally or chemically welded flashings, while torch-down flashings are standard on asphalt roofs. In addition, it’s essential to select a corrosion-resistant metal such as aluminum for flashings on shingle or tile roofs to ensure the flashing stays robust for the lifetime of the PV system.
- Structural insulated panels (SIPs). It’s important to choose a mounting system that has a lightweight, durable construction that will enhance uplift and seismic values without adding additional weight. Opt for a system with a large baseplate, allowing multiple attachments points to distribute compressive loads over standard insulation.
In the next and final post in our “Keeping It Lean in 2019” blog series on best practices for solar mounting installation, we’ll focus on how the slope of the different roof types plays a critical role in the design and installation of PV mounting systems. Click here to read the first installment of the “Lean in 2019” blog series, focused on pre-installation roof conditions. To read the entire white paper, you can download EcoFasten’s “Keeping it Lean in 2019” guide via the link.