It’s happening, you have found yourself in a situation most every homeowner eventually faces: your roof needs to be replaced! There are granules in the gutters, curling shingles scattered about, and a small leak has just developed in the bathroom ceiling. It’s time to ask yourself, “What’s the smartest way to replace it?”
For many homeowners, metal roofing has become a popular upgrade to shingles. Metal roofs are durable, pleasing to the eye, and last more than three times as long as shingles. Naturally, you’re left with another question: “Can I save time and money by having a metal roof installed over my existing shingle roof (vs. tearing it off)?” After all, it sounds like the perfect shortcut; quicker, less mess, less expense, all while gaining the durability that metal roofs are known for.
The question is fair and comes up often, but there’s a lot more to it than most realize. While metal can be installed over asphalt shingles in certain situations, it’s not recommended in most cases. Together, we’ll take a closer look at the considerations and risks before deciding on your home and learn why working with trusted local professionals is always a good idea.
5 Things to Consider Before Installing Metal Over Shingles
Before starting any roofing project, several important factors must be evaluated. This pre-project evaluation is especially important for homeowners seriously considering installing a metal roof over their existing shingle roof, which can lead to problems down the road.
- First, consider the current condition of your roof. How old is it? Is it showing signs of severe damage, such as curled shingles, severe granule loss, or even missing shingles? Does the roof already have more than one layer of shingles in place? Is it soft and spongy when you walk on it?
- The structural base under the roof, known as the roof deck, must also be evaluated. Without removing old shingles, it becomes extremely difficult to identify weak areas, assess underlying damage, and check for a solid foundation for the new roof.
- A roof is not intended to bear an unlimited amount of weight. Although metal panels are relatively light by themselves, adding them to existing shingles (requiring furring strips, which we’ll get into later) can overload your home’s structure.
- Local building codes in Michigan also play a role in determining the number of roofing layers allowed. It’s important to check the local regulations in Traverse City before adding additional layers to your roof.
- Less thought of, but no less important, ventilation must be considered when adding layers to a roof. Proper ventilation is necessary for controlling temperature and moisture. If placing metal over shingles impedes ventilation, heat is trapped, moisture levels increase, and problems ensue.
Placing Metal Roofing Over Shingles: When Might It Be Acceptable?
Although very rare, there are a couple of circumstances where moving forward with metal over shingles might make sense, including:
- When shingles are in excellent condition, only one layer, with no leaking or soft spots.
- A proper underlayment and furring system is installed before the new metal roof.
Even for roofs that meet this criterion, careful planning and professional installation are required. To ensure moving forward is the smartest approach, a professional should also confirm that your roof framing can handle the additional weight. To better understand what it takes to make this work, let’s look at how metal roofing is properly placed over shingles.
How Metal Roofing Is Installed Over Shingles
In most cases, roofing professionals view installing metal roofing over shingles as a short-term compromise more than a best-practice solution. That said, if a homeowner decides to move forward, the process differs from a standard roof replacement. Here’s what the process typically involves:
Inspection and Preparation: Professional roofers will first perform an inspection to identify any obvious issues. During this time of preparation, the ridge cap shingles are removed to allow adequate ventilation at the home’s peak once the metal roofing is installed.
Furring Strip Installation: Also called battens or purlins, furring strips are wooden strips installed directly to the existing shingles and the roof deck below. These wooden strips create a gap between the old roof covering and the new metal covering, allowing ventilation and drainage between the two layers.
Underlayment and Flashing Installation: Once the furring strips are secured, a high-quality underlayment must be installed over them to create an ice-and-water barrier. At this time, flashing is also installed around all vulnerable roof penetrations (vents, chimneys, skylights, etc.) to prevent leaking.
Metal Panel Installation: Once all steps above are complete, the new metal roof panels can be secured to the furring strips using specialized clips or screws designed for this system. To complete the assembly, the drip edge, valley flashing, and ridge caps are installed.
The Finishing Touches: Once the metal roofing is assembled, the finishing touches take place. This includes installing any pipe boots, snow guards, and trim pieces.
Although on paper this system seems to work just fine, it requires precision installation. So, what do the professionals who offer roof services in Traverse City say?
Why Experts Don’t Recommend Metal Over Shingles
As we just learned, it is possible to install metal roofing over shingles, but most experts strongly advise against it. The risks of doing so include:
Unaddressed Hidden Damage: One of the biggest concerns of leaving shingles in place is the inability to inspect what lies beneath them. The physical condition of the roof deck, underlayment, and rafters is all hidden below the shingles. By not tearing the shingles off, you can miss rotting wood, water damage, and structural weaknesses that can compromise the new roof and possibly the entire home.
Shorter Lifespan: One of the many benefits of having a metal roof is its longer lifespan. But like all new roofs, their performance and longevity all depend on proper installation. Even when following the installation steps above, putting metal over shingles can create uneven surfaces, reduce structural stability, and shorten the roof’s lifespan.
Moisture Issues: Trapped moisture is a major risk, especially in places like Michigan that experience seasonal temperature swings and moderate humidity. The gap created by the furring strips helps with ventilation, but they aren’t perfect. When heat and moisture become trapped, condensation forms under the metal, accelerating rot in the decking and promoting mold and mildew growth.
Warranty Complications: The beauty of having a new roof installed by a professional is that most offer warranties on materials and even workmanship. However, many metal roofing manufacturers limit or void their warranties when metal is placed over shingles.
Future Repair Issues: The last thing any homeowner wants to think about when a new roof is being installed is the need for future repairs. After all, that’s the reason for the new roof, right? However, homeowners need to understand that when multiple layers of roofing systems are installed one on top of the other, future maintenance becomes more difficult and expensive.
With all of this in mind, it’s easy to see that while the overlay of metal on shingles may cost less upfront, it often ends up costing much more down the road.
The Smart Choice: Professional Roof Services in Traverse City
Like most things that seem too good to be true, installing metal roofing over shingles is the same. When it’s time for a new roof, the smart choice is always a complete shingle tear-off, followed by a professionally installed metal roofing system directly onto a clean, solid deck. As experts in roof services, a licensed professional ensures a thorough evaluation of the existing roof, identifies and repairs any hidden damage, and properly installs the new roof on a solid foundation. Local companies also understand the challenges of heavy snow, high winds, and the risk of ice dams common in Traverse City and the surrounding regions. They can recommend the best approach for a roof that offers the most durability, best ventilation, and overall performance and protection.
Is It a Good Idea? NO
So, is installing metal roofing over shingles a good idea?
No, it’s not ever a good idea. Even when it may be necessary for individual circumstances (such as time and cost issues), placing metal roofing over shingles is not a smart choice.
Even when metal roofing is placed over shingles under the right conditions, in the right way, the risks far outweigh the perceived benefit of cost savings. What first seems like a quick way to upgrade your shingle roof to a metal one can lead to big problems (and expenses) later on.
When it comes to something as important as your roof, don’t settle for a shortcut. Take the time to do it right, schedule with a professional, and get the most durable, long-lasting metal roof to keep your home protected for decades.