Roof sealer is a liquid applied to various types of roofs to help protect the materials of that roof from weather damage, and can usually help extend the life of the roof. It’s usually used on flat roofs, but can be used on other types of roofs as well.
We get a lot of rain here in the Pacific NW, so roof sealer can be a good choice for a home owner. However, it’s not something you just slop on and expect it to protect your roof. To apply roof sealer, your roofer will have to clean your roof of any moss or other debris, do any repairs to missing or damaged shingles, then apply an even coat of the sealer. Most sealers shouldn’t be applied when it’s raining out.
Overall, sealer is something to use as a preventative measure. If you’re currently experiencing leaking or other roof problems, roof sealer is probably not the solution. You will likely have to get roof repairs before you should consider applying sealer.