Roof coatings get written off as paint, oversold as a cure-all, or dismissed as a short-term patch. Here's what they actually do, where they fall short, and how to tell if your roof is a good candidate.

Rust on a metal roof rarely looks urgent, but it will pull a new coating system apart from underneath if it is not dealt with first. A rust-inhibiting primer stops the corrosion and gives the coating a surface it can bond to. Below is a look at when primer is required, how it differs from a rust converter, and what tends to happen on the roofs where the step gets skipped.