How to Install Metal Roofing Over Shingles
Is your shingle roof nearing the end of its life? The constant cycle of repairs and replacements for a shingle roof can be frustrating and costly. Many property owners are looking for a more durable, long-term solution. Installing metal roofing is an excellent upgrade, offering longevity and style. But what if you could avoid the messy and expensive process of tearing off your old shingles?
The great news is that, in many cases, you can. Installing metal roofing over shingles can save you time, money, and significant hassle. This guide will walk you through the benefits, considerations, and methods for a successful roof-over project. We’ll explore how do you install a metal roof on top of an existing shingle surface and what you need to know before you begin.
Why Install a Metal Roof Over Shingles?
Choosing to place a new metal roof directly over your existing shingles is more than just a shortcut. This method, often called a roof overlay or recover, offers several compelling advantages for homeowners and commercial property owners alike.
Significant Cost Savings
One of the biggest draws of a roof overlay is the immediate cost reduction. A full roof tear-off involves extensive labor to remove old shingles, nails, and underlayment. It also includes disposal fees, which can be surprisingly high as many landfills charge extra for asphalt shingle waste. By leaving the existing shingles in place, you eliminate these expenses from your project budget, making the switch to a high-quality metal roof more affordable.
A Faster, Cleaner Installation
A traditional roof replacement is a disruptive process. It creates a lot of noise, dust, and debris around your property. For a business, this can mean interrupting operations. For a homeowner, it’s a major inconvenience. Installing metal roofing over shingles is a much cleaner and faster job. With no tear-off, the mess is minimal, and the project timeline is significantly shorter.
Enhanced Durability and Longevity
Asphalt shingles typically last 15-25 years, especially in the harsh Florida sun. A properly installed metal roof, on the other hand, can last 50 years or more with very little maintenance. By choosing to upgrade, you are essentially ending the cycle of frequent roof replacements. This long-term durability makes installing metal roofing a wise investment for your property.
Environmental Benefits
Millions of tons of old asphalt shingles end up in U.S. landfills every year. By avoiding a tear-off, you are making an environmentally responsible choice. You prevent waste from going to the landfill and reduce the carbon footprint associated with manufacturing and transporting new materials for a full replacement. Metal roofing itself is also a sustainable choice, as it’s often made from recycled materials and is 100% recyclable at the end of its long life.
Before You Begin: Critical Pre-Installation Checks
While the benefits are clear, you can’t simply start installing metal roofing panels over any old shingle roof. A thorough inspection is crucial to ensure the project’s success and safety. Here’s what you or your contractor must check first.
1. Check Local Building Codes
Building codes vary by location. In areas like Orlando, FL, which face hurricane risks, regulations are particularly strict. Most codes allow for a maximum of two layers of roofing material on a structure. If your home already has two layers of shingles, a tear-off will be mandatory. Always verify the latest local requirements before planning your project. The Florida Building Code is an essential resource for this.
2. Inspect the Roof Decking
The existing shingles will be hidden, so the underlying structure must be sound. Your contractor needs to inspect the roof decking (the wooden foundation of the roof) for any signs of rot, water damage, or soft spots. Walking carefully over the entire roof can help identify these issues. Any damaged or compromised sections of decking must be repaired or replaced before you proceed with installing metal roofing.
3. Assess the Condition of the Shingles
The existing shingle layer must provide a relatively flat, stable surface. If the shingles are extensively curled, warped, or have multiple missing sections, they may not be a suitable base. Minor imperfections are acceptable, but a significantly uneven surface can telegraph through the new metal panels, affecting the final look.
How to Install Metal Roofing Over Shingles: Key Methods
Once you’ve confirmed that your roof is a good candidate for an overlay, the next step is to understand the installation process. How do you install a metal roof properly in this scenario? There are two primary methods for installing metal roofing over an existing shingle surface.
Method 1: Installing a Batten System (Furring Strips)
This is the most recommended method for a high-quality, long-lasting result. It involves creating a new, level framework on top of the old shingles.
- Install Underlayment: First, a layer of synthetic underlayment or a similar vapor barrier is rolled out over the entire shingle surface. This barrier serves two critical functions: it provides a secondary layer of water protection and prevents the abrasive granules of the shingles from scratching the back of the metal panels as they expand and contract with temperature changes.
- Attach Furring Strips: Next, wood or metal battens (also called furring strips) are attached to the roof. These strips are screwed through the old shingles and into the roof trusses or rafters below, ensuring a secure connection to the building’s structure. This creates a grid system over the old roof.
Create a Level Plane: A key advantage of this method is the ability to create a perfectly flat and level plane for the new roof. Shims can be used under the furring strips to compensate for any dips or sags in the old roof structure. - Provide Ventilation: The air gap created between the old roof and the new metal panels is crucial. This space, known as Above Sheathing Ventilation (ASV), allows air to circulate, which helps dissipate heat buildup in the summer. This ventilation keeps your attic cooler and can significantly reduce your energy bills, a major benefit in a warm climate like Florida.
- Attach the Metal Panels: Finally, the new metal roofing panels are attached directly to the furring strips. This ensures the fasteners have a solid base to grip, creating a strong and secure roofing system.
This method provides the best performance and aesthetics, making it the superior choice for a professional metal roof installation.
Method 2: Direct Attachment to the Roof Deck
This approach is more direct and can be more cost-effective, but it comes with important considerations. In this method, the metal panels are installed directly over the shingles without a batten system.
- Lay the Underlayment: Just as with the first method, a high-quality synthetic underlayment must be installed over the shingles. This step is non-negotiable, as it protects the metal from the asphalt shingles.
- Fasten the Panels: The metal panels are then laid out and screwed down. The fasteners must be long enough to penetrate through the panel, the shingle layer(s), and securely into the wood roof deck below.
- Challenges with This Method: While this is a viable way for installing metal roofing, it has downsides. Any unevenness in the existing shingle roof can show through the metal panels, a phenomenon called “telegraphing.” This is a purely cosmetic issue, but it can detract from the clean look of a new metal roof. Furthermore, this method does not create an air gap for ventilation, so you miss out on the energy-saving benefits of a ventilated system.
Choosing the Right Team for the Job
Knowing how to install metal roofing over shingles is a job that demands expertise. While the process may seem straightforward, proper execution is key to ensuring your new roof is weathertight, secure, and long-lasting. An experienced contractor will understand local building codes, know how to properly assess your existing roof structure, and use the correct techniques for a flawless finish.
If you are considering this upgrade for your property in the Orlando area, it’s vital to work with a team that specializes in metal roofing. For a professional consultation and expert metal roof installation, our team has the experience to guide you through every step of the process.
Upgrading to a metal roof is a smart, long-term investment in your property. By installing it over your existing shingles, you can achieve that goal more affordably and with less disruption. With the right preparation and professional installation, your new metal roof will provide decades of protection and peace of mind.
FAQs About Metal Roof Installation
Yes, a metal roof can often be installed over existing shingles, provided that the underlying structure is in good condition. This method can save time, reduce waste, and make the installation process more affordable.
A professionally installed metal roof can last 40 to 70 years or more, depending on the material and maintenance. This longevity far exceeds that of traditional roofing options like asphalt shingles.
With proper insulation and underlayment, metal roofs are no noisier than other roofing materials. Modern installation techniques ensure a quiet and comfortable experience, even during heavy rainfall.
Metal roofs are low-maintenance compared to other materials. Periodic cleaning and inspections are usually sufficient to keep the roof in optimal condition and ensure its long lifespan.
No, metal roofs often reflect sunlight, which can help reduce heat absorption. With proper coatings and insulation, a metal roof can actually improve your home’s energy efficiency.