Can You Install a Metal Roof Over Shingles?

Sun windows installed in new steel roof

Homeowners have the option to install metal roof over shingles but there are some concerns with doing so. The professional roofing contractors at Dream Roof have the onsite experience and studied practice to accurately identify some of the more problematic issues that we want to bring to your attention. Let’s check them out.

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Common Concerns with Metal Roof Installation Over Shingles

Each home has various circumstances that are deciding factors in whether or not installing a metal roof over the current shingles is a good idea. Some metal roof over shingles problems arise if your current roof has existing issues. In this situation, we will investigate the concerns to determine if the shingles need removal or repair.

Building codes are another concern that often comes up. The good news is that most building codes allow for two layers of roofing on a home. Therefore, installing a metal roof overtop your shingles should not be an issue.

Check the Roof Decking

A roof cannot sustain itself without strong roof decking in place. Therefore, it’s essential to confirm the decking’s integrity before installing metal roofing over shingles so you can rest assure the foundation of your entire roof system is up to code.

Roofers will inspect the wooden boards for signs of rotting, or whether the wooden boards are broken. Unfortunately, when you choose to install a metal roof over shingles, thereby not ever tearing down the existing roof down to its decking, the roofers aren’t given the chance to inspect thoroughly for roof issues.

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Metal Roof installation Markham

Too Much Weight?

One of the biggest concerns most people have with metal roof installation over shingles is the weight it adds to your roof. What most people don’t know is that metal roofs weigh much less than other roofing materials. Metal roofs range from 50-100lbs per one hundred square feet, while shingles range from 275-425lbs in comparison.

As a result of the wear and tear on your current shingles, installing a metal roof overtop will likely weigh less than the initial installation of your shingles. In short, the weight of your roof after installing a metal roof is a non-issue.

RELATED ARTICLE: Pros and Cons of Metal Roofing

The Weight of Installing Metal Roof Over Shingles

If your decking’s wooden boards are broken or brittle from rotting, then it will not be able to hold added weight. If your decking’s integrity is compromised, the extra weight from installing a metal roof can do structural damage to your roof over time and even impact the structural integrity of your home.

Broken or rotted wooden boards will not go away or fix themselves so adding weight will only continue to add to the problem.

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Essential Roofing Components Cannot be Replaced

By installing metal roofing over shingles, you cannot replace essential roofing components and materials such the underlayment, decking, gutters, flashing, and more. Bypassing demolition will save you money upfront, however, if roofing problems exist and are not addressed, then the future expenses will be costly, not to mention dangerous.

Tearing off your roof down to its decking is the opportunity for roofers to inspect whether any materials and components have reached the end of their lifespan. Skipping the inspection means your roof will have to rely on materials from the old roof system. For these reasons, roofers recommend a complete tear-down before installing a new roof to keep your home and family safe.

Leaks will be Harder to Detect and Replace

Installing a metal roof over shingles makes finding, tracking, and repairing a roof leak much more difficult because the source of the leak could be coming from two different parts of either the old roof or from the new metal roof. Leaks are problematic for obvious reasons in that if water gets underneath your metal panels, you may begin noticing leaks are starting inside your home.

If in fact the origin of the leak is from your old shingle roof, then your roofers will need to tear up the metal roof to repair the issue. If you are committed to installing a metal roof over shingles, it’s imperative you ask your roofing contractors beforehand that your current roof shingles are in well enough condition to undergo this process. If you already have roof leaks, it’s best to not go through with adding onto the problem with another roof.

RELATED ARTICLE: Metal Roof Installation Guide

Old Asphalt shingles curl

If the Foundation is Bad, it’s Bad! It’s Not Going Away

If your old shingle roof has issues, then installing a metal roof will not rid your roof of all its problems. If the foundation has its faults, then adding another layer only covers up the issue, without ever addressing the root of the complication head-on. This can lead to costly and potentially alarming results that impact the roof as well as the house as a whole.

The components and materials will still continue to age, the wooden boards will still continue to rot or stay broken, and the water leak will still continue to exist. The same issues will be present whether they existed because of your old shingle roof, or now with a new metal roof covering.

Roof Shingles vs. Metal Roofing

The right roof that is best for your house depends on factors such as your budget, design, your property’s lifecycle, the weather, your municipality, and more. Both materials are great options for residential roofing, it just depends on what you’re looking for that will determine whether shingles or metal is better suited to meet your needs.

In general, shingle roofs are cheaper up front and easier to install and repair, whereas metal roofs are more eco-friendly and tend to be more durable.

Why Choose Metal?

At first, metal roofing may seem like an odd choice, but it surprisingly stacks up well against traditional roofing materials. Metal roofing tends to outlast shingles as the sun’s heat does not do nearly as much damage as it does to conventional shingles. Aside from durability, the many other benefits of metal roofing include:

  • Waste reduction. Metal roofs last longer, which means you won’t have to feel guilty about dumping your old shingles away every few years.
  • It will save you money in the long run. Traditional shingles need replacement often, which means you’ll likely be spending more on repairs. With a metal roof, you get the job done right and enjoy little to no maintenance needed.
  • An added layer of protection. When installing a metal roof over shingles, you’ll always have that extra layer underneath to protect your home in the event of an unexpected storm.


How to Install Metal Roofing Over Shingles?

Professional roofing contractors can proceed installing a metal roof over shingles in one of two ways. The first is a more expensive but higher-quality approach. Install 1-inch by 4-inch purlins over the shingles. The second-best way is a faster option but does not provide the flattest surface for metal roofing installation. It requires you to apply underlayment over the old shingles.

Can You Put Metal Roofing Over Two Layers of Shingles?

Check with your local building department to see whether you can put metal roofing over two layers of shingles. Many jurisdictions do allow one or two layers of shingles, but three is not permitted. If you have been given the go-ahead from your local building department, contact Dream Roof’s contractors to see what next steps can be taken.

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

There are a couple benefits to be had from installing metal roof over shingles. The first advantage is that shingles help insulate your home further by acting as an extra layer. The second advantage is that you can save on the labour costs of removing shingles. In addition, the old singles will not be thrown to waste into landfills.

Do I Need Underlayment for Metal Roofing Over Shingles?

For the structural integrity of the roof, it’s essential to have an underlayment. In a situation where a metal roof is being installed over shingles, the shingles may be able to fill the role as the roof’s underlayment. However, over time, if the shingles expand and contract, this can cause serious damage underneath the metal roof. Thus, we recommend removing the shingles on your home before installing a metal roof.

Is a Metal Roof or Shingles Cheaper?

Metal roofing is more expensive to install than shingles however, you may be able to see long-term benefits with metal roofing. They are designed to last significantly longer than shingles because of their durability, and they are much more resilient to Toronto’s harsh weather conditions. Metal roofs also have a unique visual appeal and have a distinct aesthetic that will surely compliment the rest of your home’s exterior.

Final Thoughts

The metal roof installation process is a lot easier than most would think. To begin, we first evaluate the condition of your current shingle roof. If there are any existing issues or leaks, we make sure to resolve them first and foremost. Once that is taken care of, we then begin to apply the metal roof over the current shingles.

Installing a metal roof overtop your current shingles does not harm your home and only provides benefits in the long run. It is an installation that is regularly done and highly recommended by steel roof installation experts.