Many homeowners today are installing metal roofs. That’s because they offer a wide range of benefits, including longevity and energy efficiency, and can withstand harsh weather conditions better compared to traditional roofs.
Now, galvanized steel is among the types of metal roofs. This material has been used for many years and is loved because of its ability to withstand rust. It is steel coated with a layer of zinc to prevent rusting. As such, it prolongs the life of the roof while slowing down corrosion.
Although galvanized steel is a common roofing material, still you’d want to know whether it’ll rust and how long it takes to. This article talks about this type of roofing to help you make an informed choice.
Does Galvanized Steel Rust?
Unfortunately, galvanized steel can rust. Although it’s coated with zinc, which prevents corrosion, some factors can make it rust. This means that while it will take a long time, your galvanized roofing can and will still rust after some years.
However, the rate and when rusting will occur largely depends on things like:
1. Relative Humidity
Moisture in the air is among the reasons that cause rusting on metal roofs. Although galvanized steel is coated, it can still be affected by this factor. If you live in an area where humidity is high, your roof can rust sooner than expected. Unfortunately, there’s nothing much you can do to control this.
Saltwater has a negative effect on metal. While some metal types are suited for coastal environments like zinc and aluminum, there’s no guarantee that they won’t rust if they constantly come in contact with saltwater.
3. Contact with Other Metals
When some metals come in contact with each other, it can cause a negative reaction, which can contribute to corrosion that wouldn’t have occurred otherwise. Galvanized steel and copper, for instance, can cause rusting if they are put together.
Therefore, be careful about this, especially during installation. Talk to your contractor about the products that will be in contact with your roof then ask if the material will react to your galvanized steel. You can also read up on the metals that will likely cause corrosion if put together with your galvanized roofing.
4. Improper Coating
Zinc coating on galvanized steel is meant to protect it from corrosion. However, if it was not properly coated, especially on the underside of the panel, rusting can take place. If water molecules are trapped between the panel and insulation, the metal can weaken if it wasn’t well-coated.
Underside corrosion is also possible if granulated underlayment was used.
How Long Will Galvanized Steel Last?
Well, now we know that this material is prone to corrosion. So how long does it take for it to completely rust? A very long time. If the factors that contribute to rusting are controlled, you can use your roof for years.
Note that galvanized steel is designed for extended outdoor use, especially hot-dipped galvanized. As such, it can last for approximately 70 years depending on the environment.
If your roof is exposed to wet or soaked environments, the zinc layer on galvanized steel can take ten years to corrode, while if you live in a place with 100% relative humidity, the approximate years are 34.
Note that the ability of the zinc coating to resist corrosion depends on the type of corrosion and how thick it was. However, this is also influenced by how severe the environmental conditions are.
What Environments Promote Rust?
We’ve already mentioned that your environment will affect the length of time your roof takes to rust. Here is a list of the corrosive environments from least corrosive to most corrosive.
1. Rural Environments
These have a low aggressive corrosive atmosphere. Air and rain in these regions don’t have high sulfur levels and other corrosive emissions.
Atmospheres in these communities are less corrosive.
3. Temperate Marine
As they generally experience low humidity and temperatures, they don’t encourage corrosion so much. However, distance from the ocean, wind speed shape, and direction affect the corrosion rate.
4. Tropical Marine
Here, temperatures significantly fall and might even go below freezing. Humidity is also high, and nearby water diffuses chlorides. Plus, there are warm temperatures in these regions. All these factors can make the surface of galvanized steel corrode faster.
5. Industrial Environments
These are the most aggressive regions for corrosion. Sulfide and phosphate air pollution from sources like automobile exhaust promotes rusting of galvanized zinc.
How to Maintain Galvanized Roofing
Remove Rusted Components from Your Roof – sometimes there may be fasteners, screws, or washers on your roof that have rusted. These pose a threat to your galvanized roofing as it may also rust. Therefore, inspect your roof of these items and immediately get rid of them:
1. Remove Rust from Metal Roof
While you can do this yourself, we recommend hiring a professional cleaner. That’s because the chemicals and equipment used for removing rust on the roof can be dangerous, especially if you do not work with them correctly.
However, there are organic rust converters that are safer to use. But, they’re not as effective as rust-removing acids. Thus may not remove all the stains on your roofing. But, they can help reduce rusting in some much-rusted areas.
2. Repaint After Cleaning
Although cleaning rust improves the appearance of your roof, this won’t prevent it from rusting again in the future. Once your roof is clean, inspect it to find areas that are susceptible to rust. Then treat these areas to prevent them from rusting again.
Also, arrange for your roof to be repainted as soon as possible. Note that some paint is removed when cleaning your roof. This, therefore, exposes the rusted areas even more. It’s why you should have it repainted with a water-resistant coating. But before that, treat it with a steel primer.
3. Apply Protective Coating
The coating used when your roofing was manufactured can lose its protection capacities with time. Therefore, recoating it may be necessary to keep your metal roof functional. Experts advise that you coat every 5 to 12 years after your roof was installed.
But, this depends on where your home is located and its size.
How Much Does Coating My Metal Roof Cost?
Metal roof coatings not only prevent rust but have many other benefits too. They can prevent leaks while saving energy, which increases the life span of your roof. There are different coatings for metal roofing, including acrylics, silicone, and elastomeric.
They all vary in terms of durability, performance, and price. Your roofing contractor can help you decide which option is best for you.
Generally, how much you’ll spend on coating your roof will depend on its size. The price ranges from $2-$3 per square foot. So, for instance, if your office is 2000 square feet, it’ll cost around $4000-$6000. But, you can reduce this cost by looking for an experienced roofer who matches your budget.
How to Prevent Rust on Galvanized Roofing
Although rusting can be removed, you should prevent it if you can. Inspect your roofing regularly for signs of rust. Hotspots to check are areas around the roof screws or fixings and roof sheet overlaps. Check the screw heads as they can suffer torque damage if the coating chipped during installation.
As such, this will let moisture in, and with time the rust will spread to surrounding areas. Act as fast as possible if there are any rusting signs on your screw heads. That said, here are ways to prevent rusting;
- Repaint your roof after every few years. When the paint begins to look faded and old, it’s time you consider repainting.
- Always coat with water-resistant coating.
- Inspect all components of your roofing during maintenance, including rivets and nails. If they’ve rusted, clean or replace them.
- Clean the chimney flashing if you have one. Additionally, when priming this area, choose high heat paints as they can withstand the high temperatures.
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