NRCA Makes Recommendations for Successful Waterproofing on Rooftop PV Installations

North American Clean Energy magazine posted “Common Waterproofing Code Violations: For rooftop PV installation”, to its website, addressing recommendations for reliable waterproofing of rooftop photovoltaic (PV) systems on Nov. 28. The article in its entirety is posted below.

NRCA agrees with the article’s statement that properly flashing PV supports is critical to the successful performance of a PV system and recommends PV support stands have a flanged base or be used with a prefabricated base plate to facilitate effective flashing installation methods. In addition, NRCA recommends support stands be flashed in a fashion similar to a pipe penetration. With this detail, a proper watershedding installation is achieved by having the upper course of roof covering overlapping the upper flashing flange with the back of the flange extending beyond the headlap (asphalt shingles) or overlap (tile) of the roof covering. The bottom flange should then overlap the lower course of roof covering.

Furthermore, it is important to note the installation of a roof-mounted PV system is a commitment to a long-term incorporation of a roof system and a PV system. A roof system’s primary function is to keep a building weatherproof. Ideally, a roof system and roof-mounted PV system should have similar life expectancies. Therefore, NRCA recommends installing rack-mounted PV systems on roof systems that have equivalent or greater service lives than the PV components. If a new roof system is not installed, NRCA recommends a roof-mounted PV system be installed only with an existing roof system with equivalent service life or provisions be made during design that allow minimal disturbance to the PV panels and electrical output during reroofing.

For additional information about roof-mounted PV systems, refer to NRCA Guidelines for Roof Systems With Rooftop Photovoltaic Components. Visit

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