Mold on Mast

Paul from Florida asks: 

Hidden faster roof & boots installed 2018. This mast boot started getting moldy right away. Several times I cleaned it with vinegar but decided to stop. I know it should have been installed 45 degrees, cuz rain puddles on top edge. The boot is sagging in one area circled. It is thinner then the toilet vent boots (2) which never molded & are round. I need to fix or replace mast boot but im concerned about all those penetrations. Ideas? 

Below is what our roofing expert John Kenney from Cotney Consulting had to say in response to your question:

Paul, after looking at the photo and knowing this is a standing seam roof, my concern is still the sagging mast boot and the way water is collecting around the penetration. The surface mold is secondary. The bigger issue is whether the flashing assembly is properly shaped, supported and sealed to shed water around the mast.

With standing seam, the preferred repair is usually a properly sized pipe/mast boot or retrofit flashing specifically designed for metal roofing, installed so it conforms to the panel profile and allows for panel movement. I would avoid relying on repeated applications of sealant as the primary repair. The existing boot should be removed, the panel and surrounding fastener holes inspected, and the new flashing installed with compatible butyl tape, sealant and fasteners as required by the metal roofing manufacturer.

Your concern about all the penetrations is valid. Standing seam systems are designed to minimize exposed fasteners, so any penetration detail needs to be handled carefully. If the current flashing is replaced, the roofer should make sure old holes are properly addressed rather than simply adding another layer over the top.

My recommendation: have a contractor experienced with standing seam roofing replace the mast flashing with an approved retrofit boot or penetration assembly and verify the repair detail with the roof manufacturer. Since this is an electrical service mast, coordinate with a licensed electrician if the mast needs to be disconnected or moved during the repair.