What are the pros and cons of metal roofing? Metal roofing today can be made to look like many other roofing materials, including clay tiles, asphalt shingles, slate, or even natural wood. A metal roof is typically a larger investment up front, but over the long run it may be cheaper than even traditional asphalt roofing.
The Pros and Cons of Metal Roofing
There are many benefits to metal roofs, but there are also a few drawbacks. Metal roofs excel at life expectancy, weight (they are very lightweight), and ease of installation. A metal roof is often warrantied for 30-50 years. They are much lighter than any other traditional roofing material and can even be installed over an existing shingle roof, without need to tear up the existing roof. Metal roofs are easy and quick to install. They usually come in multi-shingle panels or large metal sections, reducing the number of individual pieces to install.
Metal roofs are also fire and rot resistant. Metal reflects heat from the sun, lowering cooling costs in warm weather. It is also a naturally slippery surface, easily shedding rain and snow while requiring less roof pitch than other materials.
The most obvious drawback is initial cost. Although a metal roof is cheaper in the long run, the initial installation is more expensive than traditional asphalt shingles. While they can outlive more traditional roofing materials, they are susceptible to dents, scratches, and peeling paint. If a metal roof does need repair, you will have to repair an entire section, since it is not installed in individual shingles like other materials.
In addition, the sound of rain on a metal roof can be irritating to some homeowners, although that can be mitigated with the right insulation and roofing materials underneath the metal. Finally, in case of an emergency, such as a house fire, that requires breaking through the roof, metal roofing can be slow for emergency personnel to cut through.
Types of Metal Roofing
The term “metal roofing” covers a wide variety of products and materials. Common metals used include steel and aluminum with various coating. On the higher end, some homes may use copper, zinc alloys, more custom alloys, or even stainless steel for a special look.
The variety of metal materials used in roofing is reflected in a variety of price ranges. Copper has a long history as a roofing material. Because it naturally oxidizes, a copper roof will develop a patina that can be a highly desirable aesthetic choice. There is also no coating that could potentially peel or otherwise degrade. However, copper is also a very expensive material. Other high-end materials include various alloys—also more expensive than aluminum or steel—and stainless steel, which can be very expensive.
You can learn more about choosing the best metal roofing material for your home here.
Residential Steel Roofing
Steel roofing is the most common metal for residential roofing. The steel roof begins as a giant roll produced at a steel mill. That roll is then coated with a special anti-rust metallic coating while it is still at the factory. This coating may be zinc or a zinc aluminum alloy.
The treated metal coil then moves on to a painting factory where the metal is coated with paint which is then baked on. The painted metal is sent to a roofing manufacturer, where the metal will be shaped into large roofing panels or pressed into individual tiles.
Steel roofing that is coated and painted stands up well to the elements. The zinc or zinc alloy coating oxidizes before the iron that is part of the steel beneath the coating. The oxidized zinc (or alloy) coating then serves as a barrier, preventing the iron in the steel core from rusting.
Installing a Metal Roof over Shingles
Metal roofing is a great investment. A typical asphalt shingle roof can last 20 to 30 years. A metal roof, when properly installed, can last 50 years or more. A metal roof can also be installed over an existing asphalt shingle roof, making it even easier to install. There is no need to tear off the existing roof.
To install a metal roof over an existing shingle roof, begin by attaching a 2×2 frame to the existing roof. The metal roof will be attached to this frame. It is best to use metal shingles. Metal roofing is available as long sheets that span the roof all the way to the eaves, but this may be less practical when installing over an existing roof.
The new metal shingles can be screwed directly into the 2×2 frame. This has a few advantages. First, installing a metal roof this way is extremely secure and the new roof can withstand winds up to 120 mph. This is because the shingles are screwed directly into the frame, which is in turn screwed directly into the rafters. There is no adhesive like with a shingle roof. Second, it greatly reduces the noise level that is one disadvantage of metal roofs. The existing roof and the gap between the old shingles and the new roof almost completely deaden the sound of falling rain. Finally, because there is a gap between the old roof and the new, the roof is very well ventilated which can prevent ice dams in the winter and keep the house cool during the summer.
Potential Problems With a Metal Roof
There are a few potential issues to be aware of when installing a metal roof. In general, metal roofs are a great long term investment. When properly installed, a metal roof can last the lifetime of the house. However, metal has some drawbacks as a roofing material. Being aware of these drawbacks can help you plan for them and avoid any big problems.
Leaks, Wind, and Dents in Metal Roofing
One possible problem is leaks. A metal roof should be leak proof and stand up to all kinds of weather, but if the roof was punctures at all during installation leaks can develop. These can be a bit of a problem to fix, since there aren’t individual shingles to replace. Rather than replace a large section of roof, you may choose to caulk the leak. Unfortunately, because metal expands and contracts with changing temperatures, caulking is not always a long-term solution.
Another problem is susceptibility to wind. Again, a well installed roof can stand up to much higher winds than traditional shingles, but if there are gaps or dents in the flashing when it is installed they can catch the winds. The large roofing panels can then act like sails, pulling up in high winds. Good installation will, of course, prevent this issue.
Also, like any metal, a metal roof is susceptible to denting. Keep foot traffic on the roof to a minimum. Luckily, a metal roof shouldn’t require much maintenance, so there’s little need to tread on the roof. However, if you must go up, tread lightly and make sure to avoid denting or puncturing the metal. Even without foot traffic, a heavy hailstorm can cause some denting. Make sure to inspect the roof after a heavy hailstorm, or a windstorm that causes heavy branches of other materials to land on the roof. A bad enough dent can break through the protective coating and lead to rust, so be sure to treat any dents you find.
Avoid Problems with Proper Installation
The best way to avoid any problems with your roof is to have it installed correctly the first time. A metal roof is a great investment and can save you time, money, and stress over the life of your home. Make sure to have it installed by a professional contractor like Eagle Watch Roofing to get the best out of your new metal roof.
How is Metal Roofing Made? [infographic]