Can Metal Roofing Be Installed Over Shingles?

Metal roofing has gained popularity in recent years due to its durability, energy efficiency, and sleek design. However, many homeowners are surprised by the cost when they first get an estimate. To reduce expenses, some homeowners are exploring the possibility of installing metal roofing over existing shingles. But is this a good idea?

When considering upgrading to metal roofing, especially in the Haliburton area, this guide provides insight about installing a metal roof over the old shingle roof. We’ll explain the advantages, potential drawbacks, and why hiring a professional, such as Country Contracting and Construction, can make all the difference.

Can You Install a Metal Roof Over Shingles?

Yes, metal roofing can be installed over shingles, but it depends on the condition of the existing roof. The shingles if nearing the end of their lifespan should be in reasonably good condition—no significant lifting, cracks, blistering, or bumps. If the shingles are in fair condition, a metal roof can be successfully installed over them, saving about 25% in labour costs to remove the old roof, install new underlayment, or pay for disposal fees.

That said, most roofs are not ideal candidates for this installation method, and even if it’s possible, it may not always be the best option. Here’s why.

Key Considerations Before Installing a Metal Roof Over Shingles

While installing a metal roof over existing shingles may seem like an easy solution, there are several critical factors to should be considered before proceeding.

Compromised Protection from the Old Roofing Materials

Old shingles that have reached the end of their lifespan no longer provide adequate protection of the home. If water manages to seep under the metal panels, it can penetrate the worn shingles, leading to hidden leaks and serious water damage. Once moisture gets under the surface, detecting and repairing these issues becomes much harder, potentially leading to expensive repairs in the future.

Challenges in Locating and Repairing Future Leaks

One of the main issues with installing metal roofing over shingles is that tracking and fixing leaks becomes significantly more difficult. If water penetrates the metal panels, it will follow a winding path across the old shingles before making its way into the home. This can make pinpointing the source of a leak extremely challenging and time-consuming. Multiple repair attempts may be needed to resolve the issue, which can quickly drive up labor costs.

Missing the Opportunity to Replace Critical Roofing Components

Skipping the tear-off process when installing metal roofing means that essential roofing materials, like the underlayment, won’t be replaced. Underlayment serves as your roof's last defense against water infiltration. If you install metal roofing over an old, deteriorating underlayment, you’re relying on a material that may be well past its effectiveness. With a full roof replacement, you’d have the chance to install proper underlayment and materials specifically designed for metal roofing, ensuring long-term protection.

Structural Integrity May Be Compromised

One major risk of installing metal roofing over shingles is that the roof’s wooden decking (the structural support) will not be inspected. When old shingles are removed during a traditional roof replacement, the contractor has the opportunity to check for issues like wood rot or structural weakness. If you skip this step and cover the decking with metal roofing, undetected problems in the wooden structure may worsen over time. The additional weight on potentially compromised structure could lead to significant

damage and costly repairs later on.