Metal Roof Over Shingles Problems: What to Know

Installing a metal roof over existing shingles is an appealing option for many homeowners, as it seems like a cost-saving solution that eliminates the need to tear off the old roofing material. However, this shortcut can lead to various problems that affect the integrity of your home and the lifespan of your new roof. 

In this guide, we’ll explore the potential issues and benefits of installing a metal roof over shingles, helping you make an informed decision.

Is Installing a Metal Roof Over Shingles Safe?

Installing a metal roof over shingles is a common practice, but it isn’t always the safest option. While metal roofs are durable and resistant to many environmental factors, placing them over old shingles can compromise the stability of both the roof and the home. The weight of the new roofing material can add strain to the existing structure, especially if the old shingles are already showing signs of wear and tear.

In many cases, the condition of the shingles and the roof decking beneath them needs to be inspected before installing a metal roof. Without tearing off the old roofing material, there’s a risk that underlying issues such as rot or mold could go undetected, leading to more significant problems in the future. For this reason, professional roofers often recommend removing the existing shingles before installing a metal roof to ensure a solid foundation and prevent potential hazards.

What are the Problems With Installing a Metal Roof Over Shingles?

Installing a metal roof over shingles might seem like a time-saving and cost-effective solution, but it comes with several risks and potential problems.

1. Added Weight Compromises Roof Integrity

One of the biggest issues with installing a metal roof over shingles is the added weight. While metal roofs are relatively lightweight compared to other roofing materials, placing them over existing shingles can put additional strain on your roof’s structure. If your shingles are old or compromised, they may not be able to support the extra load, leading to structural damage over time.

Older roofs are already under stress from years of weather exposure, and adding the weight of metal roofing can worsen any underlying issues, such as weakened roof decking. This increased weight can cause the roof to sag, resulting in cracks and leaks that damage your home’s interior. It’s essential to evaluate your roof’s current condition before deciding to install a metal roof over shingles to avoid compromising the entire structure.

2. Increased Long-Term Costs

While skipping the tear-off process might seem like a way to save money upfront, it can end up costing more in the long run. Installing a new metal roof without removing the old shingles means you are missing out on an essential step in the roof replacement process: inspecting and replacing old or damaged materials. When you forgo this step, you risk needing extensive repairs later, as underlying problems like rotting decking or poor ventilation will eventually surface.

Additionally, by not addressing these issues from the start, you may find that you need to replace your roof sooner than expected. The cost of repairs and potential damage from leaks or other structural issues can add up, making the initial savings from not removing the old shingles insignificant in the long term.

3. Limited Access to Roof Decking

One of the critical steps in roof replacement is inspecting the roof decking to ensure it’s in good condition. When installing a metal roof over shingles, this step is skipped, and any damage to the decking remains hidden beneath layers of roofing material. Problems such as rotting, mold, or water damage can go undetected, potentially leading to costly repairs later.

If these issues are not addressed, they can worsen over time, compromising the structural integrity of the roof. When it’s time to repair or replace the metal roof, the damage to the decking will likely require more extensive repairs, increasing both the time and cost of the project.

4. Increased Risk of Leaks

Leaks are always a concern when it comes to roofing, but installing a metal roof over shingles can make leaks more difficult to detect and repair. If water manages to seep through the metal roofing, it will be trapped between the layers of shingles and metal, making it challenging to locate the source of the leak. This can lead to more significant water damage over time, as water has multiple layers to penetrate before becoming noticeable inside your home.

Furthermore, the shingles underneath can retain moisture, exacerbating the problem and potentially leading to mold and rot. Once leaks become severe, the repair process can be more complicated, as roofers will need to remove both the metal roof and the shingles to access and fix the problem.

5. Shortened Roof Lifespan

A properly installed metal roof can last 40 to 70 years, but installing it over shingles can significantly shorten its lifespan. The uneven surface created by the old shingles may cause the metal panels to warp or shift over time, which can lead to premature wear and tear. Additionally, any existing issues with the shingles, such as cracks or curling, will affect the performance of the metal roof.

Metal roofs installed over shingles often require more frequent repairs and maintenance, which can erode the cost savings that homeowners hope to achieve. In the long run, the roof may need to be replaced much sooner than expected, resulting in additional expenses.

6. Risk of Mold Growth

Moisture buildup is another potential problem when installing a metal roof over shingles. Without proper ventilation, moisture can become trapped between the two layers of roofing material, creating the perfect environment for mold growth. Mold can spread quickly and lead to health issues such as allergies, respiratory problems, and skin irritation for the occupants of the home.

Furthermore, mold can damage the roof decking, insulation, and even the walls of your home if left unchecked. Addressing moisture problems early is key to avoiding more extensive damage and health risks.

What are the Benefits of Installing a Metal Roof Over Shingles?

Despite the challenges, there are some benefits to installing a metal roof over shingles.

• Aesthetic appeal: Metal roofing offers a sleek, modern look and comes in various styles to complement different home designs.

• Durability: Metal roofs are resistant to impact, strong winds, and harsh weather, making them ideal for storm-prone areas.

• Energy efficiency: Metal roofs reflect sunlight, reducing heat absorption and lowering cooling costs.

• Fire resistance: Metal roofs are non-combustible, providing extra protection in areas prone to wildfires.

• Environmental friendliness: Many metal roofing materials are made from recycled content and can be recycled at the end of their life cycle.

Maintenance Tips for Metal Roof Over Shingles

Regular maintenance can help ensure that your metal roof installed over shingles stays in good condition for many years. Here are some essential tips:

• Inspect for leaks regularly: Check both the metal roof and the shingles for any signs of water leakage, especially after storms.

• Clean the gutters: Remove debris to prevent clogs, which can lead to water backup and leaks.

• Clear off debris: Keep leaves, twigs, and other debris off the roof to prevent moisture buildup.

• Check for rust or corrosion: If you notice any signs of rust, treat them immediately to prevent further damage.

• Tighten loose fasteners: Ensure all screws and fasteners remain secure to prevent panels from shifting or lifting.

How Long Does Metal Roof Over Shingles Last?

A metal roof typically lasts between 40 to 70 years, depending on the material and installation quality. This is a significant improvement over traditional asphalt shingles, which usually last between 12 to 20 years. Metal roofing’s longer lifespan makes it a popular choice for homeowners looking for durability and minimal upkeep.

While the underlying shingles may have already reached or surpassed their useful life, the metal roof provides a strong layer of protection. However, installing metal over shingles without addressing underlying issues could shorten the roof’s lifespan due to hidden problems like moisture buildup or poor ventilation.

The longevity of a metal roof also depends on factors like climate, material type (such as aluminum, steel, or copper), and regular maintenance. With proper care, metal roofing can easily outlast other roofing materials, making it a sound investment for homeowners.

Installation Process for a Metal Roof Over Shingles

Installing a metal roof over shingles is a process that requires careful planning and attention to detail. Here’s a step-by-step guide to help you through the process:

1. Inspect the Shingles

Before starting, thoroughly inspect the shingles for damage, leaks, or wear. Check the roof decking and underlying structures for signs of weakness. If there are issues like cracked shingles or sagging areas, repair them before installing the metal roof to ensure a stable foundation.

2. Install Flashing and Ridge Caps

Flashing is essential to seal areas where the metal panels meet other surfaces, such as chimneys and vents, to prevent water intrusion. Ridge caps should be installed at the roof’s peak to provide a finished look and block water from seeping in. Properly installed flashing and ridge caps help protect vulnerable areas from leaks.

3. Lay Down and Secure Metal Panels

Begin at the eaves of the roof and work your way up, ensuring that each panel overlaps by at least 6 inches to prevent water infiltration. Secure the panels with roofing nails or screws, and apply waterproof sealant to enhance water resistance. Double-check that each panel is aligned properly to avoid gaps or uneven edges.

4. Clean Up and Inspect

Once all panels are in place, inspect the roof for any loose fasteners, gaps, or misaligned panels. Clean up the area, removing any debris or leftover materials. Ensure that the roof is watertight and secure, paying special attention to flashing and ridge cap areas.

Cost of Installing a Metal Roof Over Shingles

The cost of installing a metal roof over shingles can range from $5 to $10 per square foot, depending on the type of metal and the complexity of the installation. This cost includes materials, labor, and any additional tools or components needed for the project. While installing metal over shingles is often cheaper than a full roof tear-off, it still involves significant upfront expenses.

The size of your home plays a significant role in determining the overall cost, as larger roofs require more materials and labor. Although metal roofing is more expensive than traditional options like asphalt or wood shingles, its extended lifespan and durability make it a cost-effective investment for homeowners who plan to stay in their homes long-term.

Additionally, installing a metal roof can increase your home’s value and curb appeal, making the higher cost worthwhile. The energy efficiency and lower maintenance requirements of metal roofs also help offset the initial expense by reducing long-term energy and repair costs.

Conclusion

Installing a metal roof over shingles can be a viable option for homeowners looking for durability and a long-lasting solution. However, there are potential problems such as added weight, potential moisture issues, and hidden damage that can arise if the process isn’t done carefully. While metal roofs offer impressive longevity and energy efficiency, ensuring proper installation and regular maintenance is crucial.

If you’re considering a metal roof over shingles, roofquotes.com can connect you with top local contractors to provide quotes, helping you find the best solution for your roofing project.

FAQs

Is it safe to install a metal roof over shingles?

Yes, but it depends on the condition of the existing shingles and roof structure. Inspect the roof for damage before proceeding to avoid potential problems.

How long will a metal roof last if installed over shingles?

Metal roofs can last 40 to 70 years, but this depends on the quality of the installation and the condition of the underlying shingles.

Does installing a metal roof over shingles save money?

It can save on labor costs by eliminating the need for a tear-off, but it’s important to address any underlying roof issues to avoid long-term problems.

What are the risks of installing a metal roof over shingles?

Risks include added weight, moisture buildup, hidden damage, and a shorter lifespan if proper precautions aren’t taken.

What is the cost of installing a metal roof over shingles?

The cost ranges from $5 to $10 per square foot, depending on the material and labor involved, but the long-term benefits can offset the initial investment.