For existing roof installations, many PV installers use integrated flashing and mounting solutions as shown above. Many of the same mounting/flashing products can be used on new roofs after the roof is installed, but standard post and flashing systems are more common on new roofs. Before the roofing is installed, you can attach your stand-off posts and then the roofers can install separate waterproof flashing as they shingle the roof. This allows the roofers to ensure the waterproofing is done well, maintaining the roofing warranty.
Determine the design layout and check the roof’s integrity, then locate the rafters and set chalk lines. Align the base-plate vertical holes with rafter chalk lines and mark holes for drilling. Drill your pilot holes into the center of the rafter. Then fill the pilot holes with the appropriate sealant. Note: Not all sealants are compatible with shingles. Most roofing manufacturers will list an approved or recommended sealant so as not to cause chemical breakdown and deterioration of the roofing material. Common sealants include GeoCell 2300 or ChemLink M1.
Attach your mount. For this particular product, you will insert a grade-8 bolt through the backside of the base plate. Then, line up the base’s vertical holes with your pre-drilled pilot holes and drive two 3-inch lag bolts into the rafter with an impact drill.
Attach the post to the base. Secure the post to the base by turning the post onto the captive grade-8 bolt inside the base plate.
Step 4 & 5
As the roofers work their way up the roof slope, they will install roofing material around the posts and install the appropriate flashing. This is a common practice, and similar waterproof flashing will be installed around vent pipes and skylights.
An EPDM pipe collar is installed to waterproof the post-to-flashing connection. Once the roofers are done, you can continue with your PV installation, knowing that you’re working on a warranted roof with code-compliant waterproof flashing and mounts.