Oatey flashings provide a watertight seal for the mounting post.
Flashing is commonly used around plumbing vents, chimneys, and other roofing joints to keep water from entering and damaging the roof structure. In PV installations, it’s also used around roofing penetrations.
On composition roofs, a thin, rectangular piece of metal is typically used. One half is pushed up under a shingle, while the other half overlaps the shingle in the row beneath. For mounting standoffs, the metal sheet has a plastic collar, which fits tightly around the standoff, preventing water entry. Oatey is a manufacturer of flashings commonly used with various PV mounts.
Flashing metal roofs poses more challenges, as the roof metal must be uninstalled, cut, and then refit to allow for an overlap around the hole where the square of flashing can be inserted. Metal roofing specialists do offer flashings that don’t require an overlap but instead use sealant to secure the flashing to the metal roof. In these cases, watertightness relies solely on sealant for the life of the system.