Every summer, we talk to a number of folks in our stores who are curious about the right way to paint an old, rusting metal roof. They want to know what types of products to use, they want to know the steps involved, they want to know what cleaners they should purchase (and also, at least a little bit, they're wanting us to tell them that the surface is unpaintable and should just be left as is).
Well, sadly, for many of these folks, we don't tell them to leave it as is. You just can't do that. Metal roofs, when they exhibit signs of rust, need to be painted in order to be protected. Failing to protect and coat them properly will lead to larger and more expensive (and, of course, painful) failure down the road.
So, let's cut to the chase: if you've got an old metal roof that needs to be painted, here's what you need to do and what you should use:
- Wire Brush or a wire wheel on a side grinder.
- TSP cleaner
- Power Washer
- Rollers, Brushes, etc.
- Met'l Clad 449 Rust Inhibitive Metal Primer
- Met'l Clad or Glo-Enamel oil base topcoat in desired color
- Ladders/scaffolding as needed
- Scrub brush
- Wire brush or grind as much of the loose, flaking rust off the roof as possible. This is a critical key to the success of your project, so take the time necessary to do this part right.
- Once the rust is removed, it's best to still wash the roof down to remove any grease, grime, or contaminant that might be there. Apply TSP (mixed according to directions on label) and scrub with the scrub brush. (And this probably doesn't need to be said, but BE CAREFUL. A wet roof is obviously extremely slippery and potentially hazardous--so do as much of the cleaning as possible from a scaffold or a ladder.) Once you've scrubbed the roof, rinse it off well with a power washer and allow it to dry.
- After the roof has dried, simply apply the 449 Met'l Clad primer using a brush, roller or spray. Allow this product to dry for at least 24 hours.
- Once the primer coat has dried, we recommend that you apply two coats of your oil-based finish paint--whether it's the Met'l Clad or the Glo-Enamel. Products should have about 24 hours between coats.
- Start early in the day and quit when the roof gets too hot to work on. Working on a roof when it's extremely hot can be tough on you . . . and tough on the paint you're trying to apply.
- Exercise extreme caution. Whenever working at heights of any level, remember to take things slowly and take nothing for granted. One slip or missed footing can result in months and months of recovery time! So be careful!
- While Latex paints are absolutely perfect for the sides of metal buildings, they're not quite as durable for the roof. Remember, a roof doesn't have just the sun to deal with: it's pelted with driving rain and is subjected to Michigan winters and piled up snow. All of these things will damage a Latex paint quicker than they will an oil. So, for your metal roofs, stick to oil!