Can Metal Roofing Be Installed Over Shingles?

The Big Question: Can You or Should You?

This question comes up all the time: “Can I just put a metal roof over my existing shingles?”

The short answer? Yes, you can.

The better answer? Well… it depends. (Isn’t that always the case with construction?)

At Golden Horseshoe Roofing, we get this question from Hamilton homeowners looking for a long-term roofing solution—especially when they’re tired of fixing the same patch of shingles after every storm. Metal roofing is a fantastic option—durable, energy-efficient, and sleek as heck—but layering it on top of shingles isn't always as simple as it sounds.

Let’s break down what you need to know before making the leap. And don’t worry—we’ll keep it real with stories, tips, and just a few jokes (because roofs are serious, but we don’t have to be).

Check Your Local Building Codes First (Seriously)

Before you start dreaming of your beautiful new metal roof, you’ve gotta hit the books—or at least call your local building department.

A lot of areas in Canada (including parts of Ontario) follow a two-roof rule. That means you can’t have more than two layers of roofing material on your home. So if you already have a shingle roof, and especially if there's an older layer under that, you may be required by code to tear everything off first.

It’s not just about legality either—stacking roof on roof on roof (cue Inception soundtrack) can put extra weight on your structure, and that’s no joke.

What’s Underneath Matters More Than You Think

Imagine spending good money on a roof that’ll last 50 years, but attaching it to a plywood deck that’s already halfway to becoming compost. That’s the gamble when you install over shingles without a full inspection.

Just imagine a scenario where the shingles are 10 years old, on top of another 15-year-old layer, on top of a deck from the 90s. That’s a 30-year-old sandwich of roofing regret.

And you can’t always spot these problems from the outside. While attic inspections help (yes, we do those!), they won’t catch every soft spot or hidden rot.

At Golden Horseshoe Roofing, we always say: “What’s under the hood matters.” If your deck’s not solid, it’s worth the extra time and cost to tear off the shingles, replace bad sections, and start fresh. Your future self will thank you.

Installation Isn’t One-Size-Fits-All

There are a couple of ways metal roofing can be installed over shingles:

1. Directly on top, using a slip sheet or underlayment between the metal and shingles.
2. Over furring strips (wooden battens), which create a small air gap between the layers.

Now, option one sounds easier, but it’s got risks. If you install the metal right on top of granulated shingles without anything in between, it can cause abrasion from underneath—like sandpaper on your new roof. Not good.

If you were to ask most roofing experts, they would surely say that they would never recommend installing directly on shingles. Instead, they suggest a slip sheet like rosin paper or a proper underlayment to reduce friction and help with breathability.

Better yet? Furring strips create that important air gap, which helps reduce heat transfer and prevent moisture buildup. But even that has its challenges—like matching the height of flashing and accounting for any imperfections in your current roof deck.

Let’s Talk About Heat (And Why It Matters)

Metal roofs are famous for reflecting heat in the summer. But if you leave your shingles underneath, they’ll trap that heat. So instead of cooling off when the sun goes down, your roof stays warm for hours. Kind of defeats the purpose, right?

Some tips to combat the heat issue are: adding kraft-faced insulation or using radiant barriers like Sharkskin to block that transfer. We’ve used these at Golden Horseshoe Roofing on some of our Hamilton projects, especially for clients who wanted better energy efficiency year-round.

And hey, if you want to get real fancy, a cross-hatched batten system allows for true ventilation—air flows eave-to-ridge instead of just side-to-side. It’s a bit more work, but your roof will breathe better than a yoga instructor.

So… Should You Do It?

Here’s where it all comes together.

Yes, you can install metal roofing over shingles—but only if:

• Your local building code allows it
• Your existing deck is in great shape
• You use the right underlayment or furring system
• You’re working with a roofer who knows their stuff (👋 hi there)

If you check all those boxes, go for it! But if there’s any doubt about what’s underneath—or you want your new roof to truly last 40–50 years—we’d strongly recommend tearing off those shingles and doing it right from the start.

At Golden Horseshoe Roofing, we specialize in high-quality metal roofing installations all across Hamilton and the Golden Horseshoe region. Whether you’re starting from scratch or exploring a roof-over, we’ll walk you through all your options and help you make the best decision for your home—and your budget.

Final Thoughts (And a Few Words of Wisdom)

Roofing isn’t just shingles and screws—it’s a long-term investment in your home. And while going over shingles might save a few bucks now, it could cost you way more in repairs (or regrets) later on. As we like to say: “if I was looking at putting a 40, 50 year roof on… I’d want to make sure what I’m attaching it to is going to last just as long.”

So if you're curious about metal roofing, or wondering whether your shingles can stay or should go—give us a call. We’re happy to inspect your roof, review your options, and help you sleep a little easier (under a great roof, of course)!