With the increasing popularity of metal roofing due to its durability, energy efficiency, and long lifespan, many homeowners are considering it as a viable roofing option. However, one of the most common questions is whether it is possible to install a metal roof over existing asphalt shingles.
The short answer is yes, it is often possible, but it depends on various factors such as local building codes, the condition of the existing asphalt shingles, and the structural integrity of your home’s roof.
In this blog, we’ll take a closer look at what you need to know about installing a metal roof over asphalt shingles, the benefits and challenges, and the process involved.
Overview of Asphalt Shingles and Metal Roofing
Before we discuss the installation process, it’s essential to understand what asphalt shingles and metal roofing are and why homeowners are increasingly making the switch to metal.
What Are Asphalt Shingles?
Asphalt shingles are one of the most common roofing materials in the United States. They are affordable, easy to install, and come in various styles and colors. Typically, asphalt shingles are made from a fiberglass mat that is coated with asphalt and topped with ceramic granules. While asphalt shingles are budget-friendly, they are less durable than metal roofs and may need to be replaced after 15-30 years, depending on the climate and the quality of the materials.
What is Metal Roofing?
Metal roofing is made from various metals, including steel, aluminum, copper, and zinc. These roofs are known for their strength, longevity, and ability to withstand extreme weather conditions, such as heavy rain, snow, and high winds. They can last anywhere from 40 to 70 years, depending on the type of metal used and the conditions in which the roof is installed. As more homeowners seek long-lasting, sustainable, and energy-efficient roofing solutions, metal roofing has become an increasingly popular choice.
What is A Roof-over, and When is It Possible?
A roof-over refers to the process of installing a new roof over an existing one without fully removing the old roof. This method involves placing a new layer of roofing material over the current roof, which can save time and reduce the cost of a full roof replacement. It is often done in situations where the existing roof structure is still in good condition and can support the additional weight of the new roofing material.
A roof-over is a cost-effective and time-saving solution when the existing roof is in good condition, can support additional weight, and meets local building codes. It’s essential to consult with a professional roofing contractor to evaluate whether a roof-over is appropriate for your specific situation.
When Is a Roof-Over Possible?
A roof-over is generally possible under the following conditions:
- The Existing Roof is in Good Condition: For a roof-over to be effective, the existing roof must not have severe damage, leaks, or structural issues. If the old roof has significant wear, sagging, or any other issues, a complete roof replacement is recommended. Roof-overs are usually done when the current roof is still functional but needs an upgrade or a new layer for protection.
- The Existing Roof Can Support Additional Weight: The structure of the current roof must be able to bear the weight of the new roofing materials. Metal roofs, for instance, are lightweight and may be a good choice for roof-overs because they do not add too much weight to the existing structure. However, heavier materials like tiles or certain shingles may not be suitable without reinforcing the roof.
- No Local Building Code Restrictions: Some municipalities or homeowner associations (HOAs) have building codes or regulations that limit the number of roofing layers allowed. For example, in some areas, you are only allowed to install one or two layers of roofing material. It’s important to check with local authorities to make sure a roof-over is allowed in your area.
- The Roof’s Structure Is Properly Ventilated: Proper ventilation is crucial for the performance of any roof. If the current roof is poorly ventilated, it can lead to issues like moisture buildup, which may cause mold, mildew, or rot. Before proceeding with a roof-over, it’s important to inspect the attic or the space beneath the roof to ensure that there is adequate ventilation to allow for air circulation.
Benefits of a Roof-Over
- Cost-Effective: Since you don’t need to remove the old roof, you can save on labor and disposal fees, making a roof-over a more affordable option.
- Faster Installation: With less labor required for removal and disposal, the new roof can be installed more quickly.
- Less Disruption: A roof-over minimizes the disruption to the occupants of the building because the process does not involve tearing off the old roof, which can be noisy and messy.
When Is a Roof-Over Not Possible?
A roof-over might not be a viable option in the following situations:
- Severe Damage: If the existing roof has extensive damage, such as leaks, sagging, or rotting, it will need to be replaced entirely.
- Structural Issues: If the roof structure is not strong enough to support additional weight, a roof-over would not be recommended, as it could compromise the structural integrity of the building.
- Building Code Restrictions: Some regions have regulations limiting the number of roof layers allowed. If these restrictions exist, a roof-over may not be possible.
Can a Metal Roof Be Installed Over Asphalt Shingles?
Now that you have a better understanding of both roofing types, let’s dive into the main question: Can you install a metal roof over asphalt shingles?
The answer is generally yes, but there are some factors to consider. Installing a metal roof over asphalt shingles is commonly referred to as a “roof-over” method. Instead of tearing off the old shingles, a new layer of roofing material is installed directly over them. This method is typically chosen because it can save time, money, and effort in the roof replacement process.
- Building Codes and Local Regulations
The first thing to check before considering a metal roof installation over asphalt shingles is your local building codes. While it’s legal in many places, some areas may have restrictions about the number of roofing layers allowed on a home. In some places, you may only be allowed to have two roofing layers, and if you already have a layer of asphalt shingles, adding a metal roof could exceed that limit.
In some regions, building codes may require the removal of old roofing materials to prevent potential structural problems. It’s essential to check with a local contractor or your municipality’s building department to ensure that installing a metal roof over asphalt shingles is permitted.
- Condition of the Existing Roof
The condition of your current asphalt shingles is another critical factor. If the shingles are in good condition and the roof structure is solid, you may be able to install a metal roof over them. However, if the existing shingles are damaged, curling, or compromised in any way, it’s best to remove them before installing a metal roof.
If the existing asphalt shingles have been through multiple weathering events or are showing signs of wear and tear, they could cause issues for the new metal roof. A professional roofer will inspect your roof and advise you on whether a roof-over is feasible or whether you need to replace the asphalt shingles first.
- Cost Efficiency of Re-Roofing Over Asphalt
One of the most attractive reasons homeowners consider installing a metal roof over asphalt shingles is the cost savings. The process of installing a metal roof over an existing roof is generally less expensive than tearing off the old shingles and replacing them with a new material.
By skipping the removal of the old shingles, you save on labor costs and disposal fees. While you may not save money on the actual metal roofing materials, you will still benefit from the faster and more efficient installation process.
Pros and Cons of Installing Metal Roofing Over Asphalt Shingles
Pros
- Cost Savings: Skipping the removal of old shingles reduces overall costs, including disposal fees and labor.
- Faster Installation: Installing metal roofing over asphalt shingles is quicker than starting from scratch because the old roof is already in place.
- Energy Efficiency: Having two layers of roofing can improve insulation, helping to reduce heating and cooling costs.
- Less Waste: Installing over an existing roof can prevent the need to dispose of old shingles, keeping them out of landfills.
- Improved Durability: Metal roofs are highly durable and can withstand extreme weather conditions. Adding a metal layer over asphalt shingles can extend the lifespan of your roof.
Cons
- Potential Weight Concerns: Adding an extra layer of roofing may increase the weight on the roof structure, especially if multiple layers of shingles already exist. This can cause problems if the house’s framing is not designed to bear that weight.
- Hidden Problems: Installing a new roof over the old one might conceal existing problems in the underlying structure, such as water damage, mold, or deteriorating decking.
- Limited Aesthetic Choices: Some homeowners may feel that installing metal roofing over asphalt shingles reduces their aesthetic options because they might not want to hide the look of the shingles entirely.
- Voided Warranty: Some metal roofing manufacturers may void their warranties if the roof is installed over an existing layer of shingles. Be sure to confirm the warranty conditions with the manufacturer.
The Process of Installing Metal Roofing Over Asphalt Shingles
The installation process of metal roofing over asphalt shingles can be broken down into several stages.
- Preparation: Before installation begins, a professional roofer will inspect your current roof. Any damaged or compromised shingles may need to be repaired or removed. It’s also crucial to assess whether the roof structure can support the additional weight.
- Underlayment: A layer of underlayment (typically synthetic felt or rubberized material) is laid over the existing shingles. This provides an additional layer of protection against leaks and water damage.
- Installing the Metal Roof: After the underlayment is in place, the metal roof panels are installed on top of the shingles. These panels are securely fastened using screws, and the metal sheets overlap each other to ensure proper water runoff.
- Finishing Touches: The final stage involves installing flashing, ridge caps, and trims to seal the edges of the roof and ensure a watertight seal.
How to Ensure a Proper Metal Roof Installation Over Asphalt Shingles?
To ensure your metal roof installation goes smoothly, here are some tips:
- Hire a Professional Roofer: It’s crucial to hire a licensed and experienced roofing contractor to install a metal roof over asphalt shingles. A professional will be able to assess the condition of your existing roof and ensure that the installation is done properly.
- Choose the Right Metal Roof System: Different types of metal roofing systems work best for different situations. Make sure to select a roofing system that is suited for installation over asphalt shingles.
- Ensure Proper Inspection and Maintenance: After installation, it’s essential to schedule regular inspections and maintenance to ensure the roof remains in good condition and to address any potential issues early.
When Should You Not Install a Metal Roof Over Asphalt Shingles?
While installing a metal roof over asphalt shingles can be a great option for many homeowners, there are some situations where it’s not advisable.
- Damaged or Deteriorated Roof: If your asphalt shingles are damaged, curling, or failing, installing a metal roof over them may not be the best option. The existing damage may lead to further issues down the road.
- Multiple Layers of Asphalt Shingles: If your roof already has two or more layers of shingles, installing metal roofing over them could cause weight and structural problems.
- Structural Concerns: If the roof structure is not in good condition or cannot handle the additional weight of metal roofing, it’s essential to remove the old shingles and inspect the framing.
- Water or Mold Issues: If there are signs of water damage or mold between the shingles, it’s best to remove the old roof and address these issues before adding a new one.
Alternatives to Installing Metal Roofing Over Asphalt Shingles
If installing a metal roof over asphalt shingles isn’t the right option for you, here are some alternatives to consider:
- Complete Roof Replacement: If your existing roof is in poor condition, it’s better to remove the old shingles and replace them entirely with a new roof. This ensures that there are no hidden issues and provides a fresh start.
- Re-Roofing with Asphalt Shingles: If metal roofing isn’t an option for you, you may choose to install a new layer of asphalt shingles on top of the existing shingles.
Conclusion
Installing a metal roof over asphalt shingles can be a cost-effective and time-saving solution for many homeowners. However, it’s important to consider the condition of the existing shingles, local building codes, and the weight-bearing capacity of the roof structure before proceeding. Consulting with a professional roofing contractor is key to ensuring the success of your project. With the right materials, installation, and maintenance, a metal roof can provide decades of protection and enhance your home’s value.