When searching for a roofing material that will look great on your home, you may want to look past the usual asphalt shingles or clay tiles. While less common than other roofing materials, metal roofs are durable, weathertight, fire-resistant, and aesthetically pleasing. Read our answers to some frequently asked questions about metal roofs to learn how this roofing material could be a good fit for your home.
Why metal roofing?
The main benefits of metal roofs are their fire-resistant qualities, longevity, and speed of installation. The material is also surprisingly lightweight and great at reflecting heat from the sun, a characteristic that helps homeowners save energy and possibly qualify for tax credits.
According to McGraw-Hill Construction and Analytics, growing numbers of people are installing metal roofs in both new construction and roof replacement projects. Estimates show that 750,000 U.S. homeowners chose metal roofing for their residences as of 2015, forming an 11 percent share of the roofing market - making metal roofing the second choice only to asphalt shingles.
What is metal roofing?
Metal roofing is produced from a variety of materials, including steel, aluminum, stainless steel, copper, and zinc alloys. Naturally, each type of metal roofing differs in durability, price, and appearance. Steel and aluminum are by far the most commonly available metal roofing materials, as they are both relatively economical, durable, and hold paint finishes well.
Steel: Most metal roofing is made from steel, which is heavier and sturdier than aluminum.
Aluminum: A very lightweight, relatively soft metal that is less rigid and more prone to denting and damage than steel. On the other hand, aluminum won’t rust or corrode the way steel an if the finish is compromised.
How is metal roofing installed?
In most cases, a new metal roof would be installed by a licensed roofing contractor. Whether you are a do-it-yourself kind of person or a curious homeowner thinking about the metal roof installation process, the first steps are to gather all the necessary supplies, remove your old roof, and then install a layer of insulation followed by the new metal roof.
Like any roofing project, installation is best performed on a dry and sunny day in order to minimize the chance of any water or moisture damage to your house. Following the removal of all old roofing materials, exposing the roof frame and plywood sheathing, a layer of insulation is installed. Typically, a layer of roofing felt will be enough insulation, but in locations with very dramatic weather conditions, your roof may require two layers of insulation.
Next, the eave flashing, or edging, is installed to seal off the metal roof. After the flashing, the metal panels that make up the “metal roof” are installed over all surfaces of the roof.
To finish, the installer should ensure that every square inch of the roof is covered in metal, the entire perimeter is protected with edge flashing, and all the roof joints are protected with flashing.
Can a metal roof be put over shingles?
Yes, you can install a metal roof over a shingle roof, especially since it is a lightweight material.
First, you will need to check with your local building department and ask if this is an approved installation method. They will want to make sure that the plywood beneath the existing shingle roof is in good shape, allowing the screws to securely fasten to the roof.
There are two ways to install a metal roof over a shingle roof:
The first way is to run new underlayment over the existing shingle roof completely covering the old roof. The new underlayment will act as a second line of defense in case water gets underneath the metal roof, also acting as a buffer between the back of the metal roof and the granulated, rough shingle roof.
The second way is with the use of purlins or battens. The purlins are screwed or nailed down to the roof deck, and then the metal is installed to the purlins. Purlins give the installer a flat surface to install the metal roofing panels down to without the irregularities of shingles. The air gap it creates between the metal roof and the existing shingle roof will act as a buffer instead of the metal heating up the shingle roof below.
Can a metal roof be painted?
Metal roofing can be painted as long as you prepare the surface of your roof correctly, choose the right primers, paints, and sealants, and apply your products correctly. Painting your metal roof can extend its life and help make your home more energy efficient.
Most metal roofing materials come in an array of colors, but if you want a change in your roof’s appearance, newly installed metal roofs should be allowed to weather for at least 6 months before you apply paint.
Steel and aluminum metal roofing hold paint well. A coating of epoxy primer offers adhesion and a baked-on acrylic top coating adds color and protection. Because some sheet systems are designed for commercial applications, they are generally given highly durable paint finishes. Another premium finish applied to roofing tiles is stone coating, which mimics the look of tile roofing.
Are metal roofs noisy?
Metal can be noisier than other types of roofing, especially during a heavy rain or thunderstorm, but extra layers of solid sheathing or insulation installed beneath it will typically minimize the sound heard within the building.
Will a metal roof rust?
Metal does rust, but with the right protective coating, a metal roof can fight against oxidation and the formation of rust.
Aluminum metal roofing won’t rust or corrode the way steel can if the finish is compromised.
Zinc is often used as coating, and the process of applying it on the metal is called galvanization. Galvanized steel is simply steel coated with zinc. With proper maintenance, galvanized steel can last over half a decade with no signs of rust or deterioration.
Though galvanized coatings were once the best answer, a large percentage of today’s metal roofs utilize Galvalume® because it is two to four times more effective at resisting corrosion.
However, galvanized coatings aren’t recommended for use in coastal climates due to salt corrosion, or in farms where ammonia gas from manure can react with the coating, breaking it down. Also, the presence of aluminum in Galvalume® makes scratches and cut edges less protected.
What metal roof is best?
When considering the best metal roofing material, there are five main kinds of metal roofing to choose from.
Pros: Extremely long-lasting, very soft (quieter), low melting temperature, resistant to punctures unlike harder metals, 100% recyclable
Cons: More easily dented or damaged, expands and contracts with swings in temperature (can usually be controlled with the proper panel or shingle), much more expensive than other materials
Pros: Long-lasting, resistant to salt water corrosion
Cons: Natural patina over time is not as aesthetically pleasing, panels could be too thin in harsh climates, more expensive than other materials