Modern metal roofs are typically made from rust-resistant metal, or they are coated in a rust-proofing agent to keep them in good shape. But if you have a metal roof that was made several decades ago, you may notice rust beginning to appear on its surface. Luckily, this is a problem that is not as hard to address as you may imagine. Here are the steps you should follow to fight the rust and keep your roof in better shape.
Step 1: Determine how serious the rust is.
If your roof is just starting to look rusty, then chances are good that the rust is mostly still on the surface. You should be able to get rid of the rust and stop additional rust from forming without too much hassle. However, if the roof has been rusting away for several years, there is a chance the damage is too extensive to repair -- and that you'll need to have the roof (or at least the rustiest panels) replaced.
To determine the extend of the rust, climb up on a ladder, and use a broom handle to poke at various rusty parts of the roof. If they still look and seem solid, with only a bit of surface rust, you're in good shape to keep following this repair guide. If the metal seems thin or flimsy due to rust, then call a roofing company to further evaluate the damage and perhaps replace the roof.
Step 2: Sand down the rust.
Once you've determined that the rust problem is only minor, you can safely climb into the roof (on a dry day) and use sandpaper to sand away the rusty parts. Keep sanding until all of the rust is gone and the metal is smooth. For best results, start by using a coarse-grit sandpaper, and then finish up with a finer-grit sandpaper.
Step 3: Get rid of rusty debris.
Before you apply any sealer or paint to the roof, you need to make sure all of the rust you've sanded away is rinsed off. An easy way to do this is to clean your roof with a power washer. Turn it on the lowest setting, and then stand on a ladder to rinse the roof off. Start at the peak/ridge, and work your way down.
After power washing, wait 24 hours before moving on to the next step. This gives the roof enough time to dry, but not enough time for rust to start forming again.
Step 4: Apply a rust-proof sealer.
It's really best to apply a rust-proof coating to the whole roof, but this really requires an industrial sprayer. If you don't have one or access to one, then you can just use cans of sealer, only applying it to the areas where the rust was already appearing.
If you use an industrial sprayer, make sure you start at the peak and work your way down to avoid making a mess or stepping in slippery coating. Follow the same general guidelines if applying a rust-proof coating.
Step 5: Paint the roof, if desired.
If this is just a roof on a barn or shed and you don't care too much how it looks, then you can skip this last step. But if it's your home roof that you're rust-proofing, you probably want to paint it to give it a fresh, new look and cover up the inconsistent look that results from the sanding and rust-proofing. Choose paint that contains zinc, as this will help prevent future rust from forming.
If you have a sprayer, you can just spray paint the entire roof in the same way that you applied the rust-proofing agent. If you don't have a sprayer, it's probably easiest to buy a few cans of rust-proofing paint and apply it with a sponge brush. Work slowly on one area at a time. Make sure you choose a dry day to apply the paint.
If the damage is more severe and you require professional assistance, contact a company like Acoma Roofing, Inc.