Metal roofs generally have 3 problem areas.
- The fasteners loosen or the rubber washers deteriorate and leak.
- The seams leak where the metal panels join together.
- The panels themselves rust.
Coatings can be applied to a metal roof. If the coating includes special material like fabric mesh at the seams and fasteners then the coating can last more than 5 years. If special measures are not taken at the fasteners and seams the expansion/contraction that the metal goes through over the seasons will cause the coating in those areas to fail. Coating the roof without applying mesh at the fasteners and seams will only temporarily stop leaks but will prevent or slow the panels from rusting out. For the coating to stick to any rusty metal the metal usually has to be prepped by sanding and treated with some type of rust inhibiting primer. Tightening up the fasteners may temporarily stop them from leaking. Adhering EPDM to seams and caulking fasteners will also stop leaks for a period of years. Applying asphalt roofing cement to problem areas rarely lasts and makes applying better/future fixes more difficult.