How To Paint a Metal Roof: Step-By-Step Guide

Metal roofs are very important since it protects from rain, leaves, and wind. But like every metal kept outside, it is exposed to moisture and can look ugly and rusted.

A Rusty metal roof is not only an eyesore, but it can also be a hazard. Do you have a rusty metal roof that needs to be repainted?

In this step-by-step guide, we’ll show you how to properly paint a rusty metal roof to restore its original appearance and protect it from the elements. Let’s get started!

Can You Paint on a Rusted Metal Roof?

Paint is not usually recommended for metal roofs, even if it’s rusted. Painting over a rusty roof will hide the rust but won’t make it go away. The paint might stay on for a while, but moisture still gets through to the metal, which can cause damage over time.

The frequent painting also increases the chances of peeling, chipping, and cracking.

However, there are cases when the roof will have to be painted regardless of its condition. In these cases, a rust inhibitor can be applied before painting, or a protective primer coat can be used instead.

rusted metal roof

Metal Roof Facts

Some of the most common metal roofs are made of steel, aluminum, and copper.

Steel has a rough surface that is less likely to be damaged by wind-driven rain. Therefore, more paint is needed to protect it from corrosion. However, if you live in an area where acid rain or dissimilar metals are present, you might want to use stainless steel instead. It’s also more expensive but also requires fewer coats of paint.

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Aluminum has a bright metallic color that works well with any home exterior design theme. Unlike steel, this material doesn’t rust easily, even without protective coating or paint, given that it never gets wetted by acids or chemicals. With proper care and an occasional painting, though, it can last up to 50 years!

On the other hand, copper has a beautiful natural green finish that can add elegance to your home exterior. It’s very expensive though and requires regular repainting.

Other metal roofs include steel-coated fiberglass, aluminum-coated fiberglass, vinyl, and galvanized steel.

How to Paint Over Rusty Metal Roof: Step by step

What you’ll need:

A roof cleaning solution, wood stump or paint roller, a few paintbrushes, protective wear, safety goggles, and a mask.

Steps to follow

1. Clean the metal roof to remove debris and any existing coating. Use a pressure washer with a rooftop attachment or apply roofing shampoo on the roof’s surface with a brush or sponge. You can also use a pressure washer or a power washer with a stiff brush. When using the latter, wear protective gear and eye protection.

2. Once rinsed, let it dry completely in the sun. While you’re waiting for it to dry, prepare your paint according to the manufacturer’s instructions and stir or shake it well before use.

3. Use a wood stump or roller with synthetic bristles attached for painting wooden roofs. In contrast, metal ones require small paintbrushes instead of rollers because they have tighter spaces between roofing panels which is ideal when brushing on paint rolling over the roof’s surface.

4. Choose from two paints when painting a rusty metal roof – an acrylic primer-sealer or epoxy paint.

Primer-sealers protect roofing materials by preventing moisture from penetrating the shingles, while epoxy protects metal roofs against rust and corrosion.

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5. First, apply a strip of primer-sealer or epoxy paint along each side of the roof’s ridge, starting from the bottom upwards. While applying the first coat, use a wide paintbrush for larger areas and small bristled ones for narrow spaces.

6. Apply another coat after 10 minutes but don’t go too thin with it to avoid dripping or pooling on either side of your house’s eaves, which can cause drips down below when it gets wet. For large roofs, allow 1 to 2 hours for the paint to dry completely before applying another coat to avoid sagging.

7. Let the last coat dry in the hot summer sun and protect it from rain for at least 24 hours or more depending on its thickness and drying time between coats for best results. Using a primer-sealer, allow it to cure for three days before putting any heavy loads on the roof, such as snow, furniture, and plants.

8. Once completely dry and all three coats have been applied, use protective metal paint containing fiberglass to prevent scratches and corrosion. For extremely rusty roofs, you might need to apply up to 5 or 6 coats of protective paint before it can hold up against flaking and peeling.

You can also apply thick coats rather than several thin ones to speed up the process and reduce costs; however, it’s recommended that you use a roller with synthetic bristles for obtaining even coverage over large surfaces.

9. Clean your paintbrushes after use by soaking them in mineral spirits or roofing shampoo until they’re ready to use again.

Frequently Asked Questions

How do you get rid of rust before painting?

You can apply rust-removing chemicals with a brush to remove rust before painting. You can also drill holes along the edges of the metal to remove loose pieces of rust and wipe down the area with a turpentine cloth.

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What is the best primer for rusty steel?

Rust-Oleum High-Performance Rusty Metal Primer is the best primer you can apply on rusty metal roofs. This Rust-Oleum High-Performance Rusty Metal Primer seals rust with its permeating, oil-base formula that dries to a tough finish.

Can you paint a metal roof with a roller?

Yes, you can paint a metal roof with a roller as long as it’s metal roofing paint. Use a high-quality roller for smooth and even results.

What kind of paint do you use on a metal roof?

The best paint to use on a metal roof is the rust-inhibiting metal primer which you can apply over the top layer of rust and underneath the new topcoat of paint. You can also use a high gloss enamel if it’s exterior paint. Use a brush for corners and tough areas while using a roller on large surfaces.

Is it expensive to paint a metal roof?

It’s not that expensive to paint a metal roof. The price of painting depends on the size of your roof, so it can cost less than $100 for small roofs, while larger ones are priced at about $300 or more. 

How long does paint last on a metal roof?

Metal painting lasts around 5 – 10 years, depending on the quality of paint and weather conditions. You can, however, extend its lifetime by applying rust-inhibiting metal primer underneath the new topcoat of paint for maximum protection against corrosion.

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