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It is inevitable that eventually, your roof will begin to fail. This part of your home is constantly exposed to natural elements, which causes damage to even the most resistant material. Although asphalt shingles have proven to be perfect for this job, even they need to be replaced. Maybe it’s time to change them for a metal roof, and contrary to what you think, there is no need to remove your current roof to make it work. If you want to know how to install metal roofing over shingles, you have come to the right place.
When it comes to metals, many alternatives are perfect for waterproofing the roof, such as copper, aluminum, or even zinc. The most popular is steel, which is why manufacturers like Denton Roofing Company have decided to give them different shapes to make it more attractive. If you already found the perfect metal roof, then the time has come for you to learn how to install it.
No need for an additional expense
Metal is a material that has the advantage of being light, so it can rest on the pre-existing structure of asphalt and tile roofs. Installing a metal roof over shingles is more common than you think. Many homeowners choose this alternative to reduce installation costs.
Although it sounds obvious, overlaying a metal layer over your tile roof will give you additional insulation. Another positive aspect of installing metal over the existing roof is that you will not have to remove the old tiles, which again translates into lower costs.
One problem with metal ceilings is that they are very noisy. That is why it is used in factories where they do not disturb, but in residences, it is not acceptable. However, since there are tiles and asphalt under the metal roof, these will muffle the sound, drastically reducing the generated noise.
However, just because it can be done doesn’t mean you can start the project right away. There are a couple of things you need to verify before you start it. The first thing is that your city’s building codes allow it. In most states, you cannot have more than two roof layers. Once this limit is reached, all you can do is remove the existing ones.
Another important aspect is that it is not recommended to install a metal plate on a roof in poor condition. Rotten or broken ceilings will not work as support for replacing a shingle roof with a metal roof. Since the metal sheets will be bolted, any excessive force could knock them out of place.
If you’ve already verified these points, you’re ready to learn how to install metal roofing over shingles, but first, you should know its benefits.
Benefits of putting metal roof over shingles
Image source: Whitten Architects
Although people once hated installing metal roofing, it has now become a common choice among people. Thanks to new technologies, it has been possible to eliminate some of the negative points that the metal had when compared with asphalt and tile roofs, such as appearance. Manufacturers have managed to perfectly hide the material.
Some of the advantages of metal ceilings are:
- Metal is the lightest roofing material available on the market, so it doesn’t compromise the integrity of your home’s structure.
- Thanks to their weight, they can be installed over other ceilings.
Image source: Smith & Vansant Architects PC
- Those who already have a previous roof will enjoy extra protection against the weather and noise. This is especially useful to prevent leaks.
- The metal roof has a noise level similar to tiles when installed together.
- The materials used for metal roofs do not attract lightning, so they are safe. They are also fire-resistant, and insects cannot pierce it.
- The metal price tag is lower than that of other materials.
- Unlike a tile roof, metal can last up to 50 years before needing to be replaced.
- When its useful life has ended, the metal roof can be recycled.
How to install metal roofing over shingles: different methods
Image source: Dan Nelson, Designs Northwest Architects
Although there are several methods, the basic idea to install metal roof over shingles is the same in all cases. You need a solid support over your current shingles to be able to screw on the metal plates.
This is why it cannot have loose, rotten or perforated sheets. If your current roof has any of these characteristics, you will need to replace the damaged areas first.
Also, consider that your roof may not be prepared for additional weight. If you see signs of buckling or any other deformation of the ceiling from inside your home, it is best to consult an expert for advice on the project’s feasibility.
You are now ready to learn the two methods for installing a metal roof over shingles.
Using a synthetic base
The first method requires the installation of an insulating layer between the tile roof and the metal sheets. This layer is generally made of plastic derivatives and papers, such as tarpaper (although its use has been replaced by other options).
This layer is required to protect the metal from the shingles, otherwise, it could corrode and rust. Because the metal will constantly contract and expand due to heat, the friction generated could quickly damage both roofs.
The process is simple. The paper adheres to the tiles like a new asphalt mantle, and later the metal roof is placed over it.
This method has some benefits that are important to highlight. This base between the tiles and the metal, in addition to allowing the metal to slide without damage, works as an additional insulating layer against possible leaks that the roof may have. It will also work as an additional insulator for weather and noise.
Using purlins and battens
There is an alternative where it is decided to dispense with the use of the additional insulating layer for the installation of the metal roof. This uses a set of straps or purlins that are screwed along the ceiling, working as a support for the metal plates.
Using purlins as a base for the metal allows its installation to be more practical since it offers a stable floor on which to lean.
In the same way, the belts will keep the metal roof away from the old tiles and asphalt, so that corrosion is completely avoided.
The purlins offer much more resistance than the first method since a strap and a sheet of plywood support the metal. The process, however, can be a bit more complicated than if you installed a synthetic layer, so it is recommended that a professional do it.
Ending thoughts on how to install metal roofing over shingles
Knowing how to install metal roofing over shingles is only part of the process. Now that you have the knowledge, you should foresee some aspects. The most important thing is your safety. The roof is one of the most complex areas to work due to its height and lack of lateral protection. That is why you will need extreme caution.
Additionally, installing metal roofing over shingles has its inherent material risks. You will need suitable protective equipment to avoid accidents while working.
At the construction level, if you plan to install a new roof over an existing one, it must have openings that allow hot air to escape and not accumulate. If your ceiling is a flat sheet, then the purlins or synthetic mantle will need to be placed at a discontinuous rate to create these vents.
Certain spaces, such as drip edges, must be insulated using foam so that water does not penetrate the ceiling. The same will apply to other construction elements that come out of the ceiling, such as fireplaces, but instead of using foam, you should use flashings.
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