How to Paint Over an Old Rusted Metal Roof?

Painting Metal Roof

Metal roofs are normally made from galvanized steel, copper, or aluminum.

Most of them are quite strong and highly resistant to the elements, simply because they are treated with a rust-inhibiting coating to prevent corrosion from occurring.

However, this coating can weather and become scratched which means that rust can form and start to penetrate the metal sooner or later.

If left untreated, holes can also develop in the corrugated metal roof due to exposure to regular moisture.

Repairing and repainting your old metal roof with the color of your choice is the right thing to do which can extend the lifespan of your roofing.

Repainting a Corrugated Metal Roof

Metal roof painting, in particular, will offer you plenty of benefits for your home. Some of these advantages include:

  • Painted metal roofs improve the aesthetics of your home’s exterior
  • Metal roofs, that are lightly colored and reflective, are sustainable and energy efficient
  • They can last twice as long as other materials (like asphalt shingles) and can easily be recycled at the end of their lifespan

Once, you know the benefits to repaint your metal roof, here is the step-by-step process you can follow…

Step 1- Secure Yourself

Working on your roof might involve dealing with power lines and high ladders that can be risky if you do it alone.

For DIYers, it’s good to get the help of your friend or your spouse, so that you can work safely.

Maybe you can thank them later for their efforts by buying them a pizza, a beer on your next weekend.

To work in a safe environment consider wearing non-slip shoes and a harness with a safety rope.

Do not forget to anchor the rope securely to a nearby tree or any other part of your home.

Step 2- Clean the Roof

After you have secured yourself it’s time to get up there and perform some prepping job for your bare metal roof before painting.

First, you will want to remove the old paint layer by scraping away the loose paint – use a putty knife or a paint scraper tool.

You will need to do this gently so that you don’t damage the metal underneath.

Then with a power washer, wash your entire roof to get rid of all the paint flakes and debris.

Wait for at least an hour or two to dry the metal roof before you start with the next step.

Step 3- Apply Rust Inhibitor Primer

In this step, the goal is to remove the rust completely. So, you should start by scraping the area with a wire brush.

Scrub the area with the brush until you see the metal underneath. Then, wipe the surface with a dry cloth to remove any flakes remaining.

Since you’ll want to stop the formation of the rust in the tracks of your metal roofing after painting, spray the area with a thin coat of rust-inhibiting primer first to keep the metal intact.

Allow the primer to dry before applying the roof cement to the hole.

refinishing metal roof

Step 4- Apply Roof Cement and Acrylic Mesh

Using a plastic putty knife, apply the roof cement to the edge of the hole. This is usually made from urethane and comes with waterproof properties.

Spread the cement around until you have an even coat that extends at least one inch past the perimeter of the hole.

Be sure to wear gloves as you do not want the cement to come into contact with your skin.

Once the cement is in place, cut two pieces of acrylic mesh that are at least one inch wider than the size of the hole.

If you do not have any acrylic mesh, you can use the same type of metal as the corrugated roof.

Take one piece of acrylic mesh and press it into the roof cement over the hole.

This will mean bending the patch as you put it into place so that it matches the shape of the metal.

Once in place, spread another layer of cement over the mesh patch and then lay the second piece of mesh patch over the cement. Press it firmly into place.

You’ll want to do this for every hole in the corrugated roof and then let the cement cure for at least two hours or as long as the manufacturer’s label states.

Once cured, apply another coat of roof cement over the mesh patches and be sure that all of it is properly covered.

This should create a watertight seal. The goal is to cover the area so that no water can penetrate.

Step 5- Apply the Roof Primer and Paint

Once you have repaired the holes, cracks, and gaps in your old rusted metal roofing material, you can now put the primer and paint.

Start by applying a thick coat of galvanized metal primer with a specialty paintbrush or a paint roller that’s designed for corrugated roof panels.

Apply the primer evenly to the entire surface of your metal roof including the areas you have repaired.

Let the primer dry to touch, then apply the paint evenly with a paintbrush, roller, or airless paint sprayer.

Allow the paint to dry, for at least an hour and then recoat the roofing material for a durable finish.

What Paint to Choose for Metal Roof?

Picking the right type of paint is important for the galvanized metal roof of your home or shed otherwise it won’t stick well to the metal and all your efforts go wasted.

For all types of metal roofs (whether it’s a zinc roof, tin, steel, aluminum, or other rib metal), acrylic latex paint or an oil-based alkyd paint will work best.

When picking, make sure you confirm that it’s specifically designed to paint corrugated metal roofs.

These paints should come from a reliable brand and with attributes such as water resistance, fire resistance, insect repellent, and better UV reflection.

In case there’s confusion ask for the help of a professional roofer or an employee at the hardware store.  

The Bottom Line

No matter it’s your barn or an outdoor shed, getting their metal roof repaired and repainted is easy.

All you will need is roof cement, a mesh patch, and the right paint supplies.

For many homeowners, this is so easy that can they do this themselves without any professional help.

Hopefully, the steps above will help you get the job done fast, even if you have never done this before.  

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