Can metal roofing be installed over asphalt shingles?

Metal roofing is becoming increasingly popular for commercial and residential properties in the Detroit area. With its superior durability, longevity, energy efficiency, and eco-friendly benefits, metal roofing is an excellent option for many homeowners. But when replacing an existing asphalt shingle roof, can metal roofing be installed over the old material?

The answer is yes – metal roofs can be installed directly on top of asphalt shingles without first tearing off the old material. However, there are specific considerations that should be taken into account before making this decision. In this article, we'll discuss the pros and cons of installing a metal roof over asphalt shingles and provide some valuable tips on ensuring a successful installation.

Pros of Installing a Metal Roof Over Asphalt Shingles
The primary advantage of installing metal roofing over asphalt shingles is cost savings. Because you don't have to tear off the old material, no additional labor or disposal costs are associated with the project. This can reduce overall installation costs by up to 40%, making it more affordable for homeowners on a tight budget. Additionally, because the new roof is installed directly on top of the existing one, there won't be any disruption to your home or adjacent structures during installation.

Another benefit of installing a metal roof over asphalt shingles is avoiding potential damage from tearing off the old material. In some cases, tearing off the existing roof can damage the decking underneath or cause structural issues if not done correctly. Installing a metal roof over asphalt shingles eliminates this concern and helps ensure your home remains structurally sound.

Finally, installing a metal roof over asphalt shingles can add an extra insulation layer. This can help reduce energy costs by up to 25% and make your home more comfortable year-round.
Cons of Installing a Metal Roof Over Asphalt Shingles

​1. The primary disadvantage of installing a metal roof over asphalt shingles is that it may void your manufacturer's or contractor's warranty. If you decide to proceed with the installation, check with the manufacturer or contractor beforehand to ensure your 
security remains in effect.
2. Another issue is that metal roofs can be pretty heavy – up to five times heavier than asphalt shingles. This extra weight could cause structural problems if not adequately addressed during installation. If you decide to install a metal roof over asphalt shingles, it's essential to ensure that the underlying decking and framing are strong enough to support the additional load.
3. Metal roofs are less forgiving than asphalt shingles regarding installation mistakes. Even the slightest error can lead to water leakage and other problems down the road, so it's essential to make sure that you choose an experienced contractor knowledgeable in metal roof installation.
4. When installing a metal roof over asphalt shingles, there's always the possibility of moisture getting trapped between the two layers of material. This can cause mold and mildew growth and lead to structural damage if left unchecked. To prevent this problem, ensure that your contractor installs a vapor barrier or breathable insulation between the two layers of material during installation.
5. Finally, metal roofs can be pretty noisy during heavy rain or hail storms. If you live in an area that receives a lot of precipitation, this could become an annoyance over time. To reduce noise levels, it's essential to ensure the roof is adequately insulated with foam board or sound-dampening material before installation.
Tips for Installing Metal Roofing Over Asphalt Shingles
When installing a metal roof over asphalt shingles, here are some essential tips to keep in mind:
1-Make sure the underlying structure is strong enough to support the added weight of two layers of material.
2-Check with your manufacturer or contractor to ensure that installing a metal roof won't void warranties.
3-Install an adequate number of fasteners when attaching the metal roofing panels.
4-Make sure to seal all the seams and laps between the panels to prevent leaks.
5-Ensure proper ventilation in the attic space to avoid moisture buildup under the surface.
6-Use galvanized steel fasteners for more excellent corrosion resistance.
7-Choose a finish color for your metal roof that coordinates well with your home's exterior.
8-Inspect each panel before installation and use only materials that are in good condition.
9-Ensure that the space between metal roofing panels is at least 0.75 inches to allow for expansion and contraction.
10-Install a protective underlayment to reduce wear and tear on the underlying asphalt shingle roof.
11-If installing over an existing top, inspect it thoroughly for any signs of leaks or damage.
12-Make sure your contractor uses adequate walkways when accessing the roof during installation to avoid damaging the shingles below.
13-Inspect all areas after installation to make sure there are no gaps where water can enter.
14-Choose a low slope metal roof if installed over an already sloped asphalt shingle roof to add extra protection against leaks.
15-Install a flashing system around the chimney and other protrusions to guide water away from them.
16-Use mechanical fasteners instead of adhesives whenever possible for more excellent durability.
17-Inspect all materials before installation to ensure they are free of defects or damage.
18-Avoid installing metal roofing over an asphalt shingle roof if it is more than ten years old, as this could lead to premature failure of the system.
19-Make sure your contractor inspects all materials after installation to ensure everything is installed correctly and securely.
20-Have your contractor check the attic space regularly during and after installation for any signs of moisture buildup or condensation.

Installing a metal roof over asphalt shingles can provide many benefits, including cost savings and improved energy efficiency, but it's essential to consider all the pros and cons before deciding. Make sure you choose an experienced contractor knowledgeable in metal roof installation and consider factors such as weight load capacity and moisture control when planning your project. With the proper considerations, you can enjoy the benefits of your new metal roof for years. Motor City Roofers is here to help with all your metal roofing needs in Detroit and the surrounding areas. Contact us today for more information.