Do Metal Roofs Rust?
When it comes time for a roof replacement, one of the options you may be considering is metal, a durable option that — if properly maintained — can last for decades. In this guide, we’ll cover the benefits and drawbacks of this roofing material and address frequently asked questions, including whether metal roofs are susceptible to rusting.
The Pros of Metal Roofs
One of the greatest advantages of metal roofing is its low maintenance, which involves little more than occasional debris removal. Other benefits of metal include:
- Lightweight: Depending on the type of metal you choose, metal roofs can actually weigh significantly less than tile or asphalt roofs.
- Longevity: Metal roofs can last several decades past the install date, depending on the material and quality of the maintenance.
- Protection against the elements: Metal roofs easily withstand harsh elements like heavy rain, snow and hail.
The Cons of Metal Roofs
Some of the downsides to metal roofs include:
- Higher upfront cost: Shingle roofs are highly affordable compared to most metal roofs. This means you’ll have to pay more upfront if you want to experience the benefits a metal roof provides.
- More challenging installation: Metal roofs require more specialized knowledge to install than vinyl or asphalt roofs. Metal roofs must be fitted exactly to the measurements of your building, which can be time-consuming.
- Difficult to walk on: Whereas asphalt roofs provide friction and can be walked on easily, metal roofs are slick and tougher to navigate without the appropriate safety gear and training.
Does Metal Roofing Rust?
One of the most common questions regarding metal roofs is whether they rust and, if so, how to mitigate the risk. Metal roofs are most commonly made from either aluminum or steel, but steel roofs are usually protected by a zinc-based alloy coating that makes them resistant to corrosion. Even though the iron found in a steel roof will oxidize over the years, for the majority of the lifespan of the roof, it is the outer coating that will oxidize. However, if this outer coating is damaged, this could decrease your roof’s lifespan, which is why regular inspections are so essential.
Metal roof rust damage is a more common concern in areas near the ocean or other large bodies of saltwater.
How to Fix a Rusty Metal Roof
In this section, we’ll outline the basic steps for metal roof rust repair. While it’s recommended that you treat rust before holes or cracks develop, urethane roofing cement is effective for making patches, which can withstand intense sunlight. The steps are as follows:
- Wash your roof with water and detergent: Scrub off any mold using a scrub brush to ensure the repair materials will adhere correctly later on.
- Remove and replace any rusted screws: If metal around a fastener has rusted that results in a hole, repair the hole before you drive in the new screw.
- Scrub away surface rust: This can be accomplished with a wire brush. Afterward, sand the surface using 80-grit sandpaper. Then, apply a rust inhibitor to neutralize the remaining rust.
- Repair cracks and holes with urethane roof cement and steel roofing mesh: This includes cracks and holes around rusted fasteners. Begin by using a putty knife to spread a layer of roof cement that covers the crack or hole and some of the surrounding area. Then, using tin snips, cut a piece from your steel roofing mesh and apply it to the area.
- Apply roof cement over the mesh: Cut an additional piece of mesh, press the piece into the repair and coat it with more cement. Smooth out and flatten the final layer, and then let the roof cement dry.
- Coat all areas with a metal primer: Metal primer should be applied with a paintbrush.
- Paint your roof using metal roofing paint: Metal roofing paint can be sprayed or brushed.
Best Types of Metal Roofing Materials
The most popular metal roofing materials for homeowners include:
- Steel: Steel is one of the most affordable and widely available materials for metal roofs. However, as they are susceptible to corrosion, they have the shortest lifespan.
- Aluminum: Lightweight and exceptionally resistant to corrosion, aluminum roofs are a great choice for harsher climates or for those wanting a more decorative roof.
- Zinc: Zinc is usually a bit pricier than steel or aluminum, but it has benefits that could make it worth the price. Once zinc reacts with oxygen, it forms a patina that is highly resistant to corrosion.
- Copper: Copper is well known for its longevity, its resistance to corrosion as well as its ability to be formed into a wide variety of shapes. It’s also one of the priciest roofing materials, so be sure to get a quote from your roofing contractor for a more accurate price estimation.
Common Misconceptions About Metal Roofs
There’s a lot of misinformation regarding metal roofs, which often discourages homeowners from even considering this type of roofing material. In this section, we’ll bust five of the most common myths about metal roofs.
1. Metal Roofs Attract Lightning
Many people are under the impression that “metal attracts lightning,” perhaps because the lightning rods installed on top of buildings are made of metal. However, these rods don’t actually attract lightning — instead, the metal serves to conduct the electricity in the case of a lightning strike, channeling it down into the ground, helping prevent damage to the building.
Metal roofs, just like metal lightning rods, do not increase the likelihood of a lightning strike. The risk of a lightning strike is increased by other factors, primarily:
- Topography: The electric current of lightning takes the path of least resistance. That means it is more likely to strike higher ground, such as a hilltop or the top of a building.
- Size of the building: The more area that the building covers, the higher the chance of a lightning strike.
- Size of adjacent buildings: If your structure is close to buildings that are taller or larger, your building is less likely to be struck.
- The climate of your region: If you live in an area where thunderstorms are frequent, there is a greater likelihood of lightning striking your home. Research common weather patterns in your area to see if a metal roof is right for you.
In fact, if you’re concerned about lightning safety, metal is one of the best roofing materials. The primary reason for this is that it’s noncombustible, which is a huge advantage when it comes to lightning strikes.
Also, if you’d like to minimize the threat of a lightning strike on your building or home, consider installing a lightning protection system.
2. Metal Roofs Make a Lot of Noise
Another common misconception about metal roofs is that they make a lot of noise when it’s raining and hailing. While it’s true that some metal roofing profiles can be noisy in some circumstances, metal roofs are generally designed and installed to be just as quiet as any other type of roof.
Having said that, some homeowners actually prefer to hear the noise of rain and hail. Luckily, metal roofing can be installed so that it makes as much or as little noise as you’d like.
Here are common factors that affect how noisy a metal roof is:
- The structure: When structural metal roofs, such as corrugated exposed fastener roofs, are installed on top of open framing, the noises from hail or rain will be louder. This is due to the lack of a buffer between the metal and the interior of the structure, such as insulation or sheathing, to muffle the sounds.
- Restriction of thermal movement: When a metal panel is not allowed to expand and contract, which is necessary for proper thermal movement, this can lead to noise problems.
- Insulation: You can also reduce noise by adding insulation to your roofing structure. Insulation is available in many varieties and can be installed below or above the roof deck. It can also be installed between rafters or purlins of an open frame. When the insulation is being installed, make sure the insulation enables proper thermal movement.
- Proper installation: The most effective way to make sure your metal roof doesn’t produce extra noise is by hiring an experienced, qualified contractor who knows how to properly install a metal roof.
3. Metal Roofs Rust
It’s true — most metals do rust or develop a patina over time when exposed to water and oxygen, a process known as oxidation. However, metals don’t necessarily rust with the reddish-brown color that the word “rust” is generally associated with. Even though most metals will rust eventually, metal sheets used for roofing are engineered and coated to prevent the formation of rust for many years.
Here’s a look at how each popular metal roofing material is engineered:
- Galvalume: Galvalume’s core component is steel that is then hot-dipped in a composite of aluminum, zinc and silicon. This material is considered one of the best, as it combines the rust-resistant qualities of aluminum with the cost-effectiveness and strength of steel. However, if galvalume is perforated, scratched or improperly maintained, rusting can occur. This is especially common on cut edges that have not been hemmed.
- Aluminum: One of the greatest advantages of aluminum roofing is that it doesn’t experience red rust, and corrosion tends to be minimal. The rust that forms on aluminum is actually white, which has a more pleasant appearance than common red rust. Aluminum is often the roofing material of choice in areas near the coast with salty seawater spray and heavy rainfall due to its ability to resist rust.
- Copper: While copper itself doesn’t rust, it does develop a patina, a protective covering that forms as a result of sun exposure and oxidation. When it shows up and the color it becomes are still not well known, but its color ranges anywhere from a blueish-green to a dark bronze.
- Zinc: Zinc, like aluminum, doesn’t develop red rust. When exposed to moisture and carbon dioxide, it actually forms a substance called zinc carbonate, more commonly known as a patina layer. This patina aids in corrosion resistance.
- Stainless steel: A chromium and steel alloy, stainless steel is rust-resistant. However, there are varieties of architectural stainless steel that are formulated specifically to develop a zinc-like patina.
Besides the metals used for sheets and coils, the paints that are applied to these metals are also designed to help prevent corrosion and rust. What’s more — if any of these metals or paints fail, a reputable manufacturer may offer some kind of paint or substrate warranty.
4. Metal Roofs Are Susceptible to Denting
Metal roofing, despite popular belief, is extremely difficult to dent and even harder to puncture. Many new metal roof owners are concerned that a hail storm will leave dents all over, but later discover that hail very rarely dents or damages a metal roof. To do any significant damage to a metal roof, the hail storm would have to be very fierce with extremely large pieces of hail.
Fortunately, a guideline in the industry known as the Standard for Impact Resistance of Prepared Roof Covering Materials was created to evaluate the hail resistance of a metal panel. Each tested product is rated on a scale ranging from 1 to 4, with 4 being the toughest and having the lowest likelihood of denting when coming into contact with hail.
If you live in a region prone to hail storms, you’ll want to consider installing a metal roof with striation or a rib roller in the panel’s flat part, as it may help to conceal any denting that may appear following a serious hailstorm.
It’s also worth mentioning that some home insurance companies offer “hail damage waivers.” It lowers the prices of your premiums but waives coverage for hail-related replacements or repairs.
5. Metal Roofs Retain Heat During the Summer Months
While it’s true that metal can hold heat for a long time when in the sun, that fact doesn’t necessarily apply to today’s metal roofing.
When it comes to sustainability, metal roofing technology has come a long way, with the creation of cool metal roofing being one of the greatest advancements in the recent past. Cool metal roofing panels have a high emissivity, which refers to how quickly the metal surface releases its absorbed heat, returning to its normal temperature. It also has a high Solar Reflective Index (SRI), which refers to how well a surface can reflect the sun’s rays, allowing the panels to absorb less heat from the sun.
Cool roofing, besides having a longer life-cycle, is also eco-friendly and energy-efficient. It is available in a wide array of finishes, colors, slope-applications and profiles.
In short, metal roofing doesn’t necessarily hold heat during the summer months.
Contact Roof RX for a Free Inspection
At Roof RX, we have installed, repaired and replaced thousands of roofs in and around Fort Meyers, FL, and we attribute our large, loyal client base to our commitment to craftsmanship and customer service. When you work with us, we will provide you with a concise strategy to handle all your roofing needs. Whether your roof has suffered storm damage from hail or wind or your roof is nearing the end of its lifespan, we make the process simple and straightforward. Whatever your request, our team of professionals will work hard to make your dreams a reality.
To receive a free inspection, get in touch with us today.