Roof Over or Do Over?


Roof Over or Do Over?

North Carolina homeowners often ask: Can a metal roof be installed on top of asphalt shingles?

It might seem counterintuitive that a lightweight roofing material can be installed over a heavier one, but the simple answer is YES. However, there are some best practices for deciding whether to invest in a “roof-over” or a “roof do-over.” We’ll explain.

  • A McCarthy aluminum roof weighs less than 1 pound per square foot.
  • Common asphalt shingles weigh 2-3/4 to 4-1/4 pounds per square foot.

In comparison, this weight factor encourages the installation of metal roofs over existing shingles.

Should you avoid installing a new metal roof over an asphalt roof?

Here are the top 2 reasons we advise homeowners not to roof over asphalt shingles:

  1. If your home’s roof has deteriorated decking, dips, or buckles, these issues should be addressed before a new roof is installed, and that may require removing the shingles.  If you choose not to remediate these problems, they will still be apparent after the metal roof is installed and severely jeopardize its protection.
  2.  If your home has more than one layer of shingles, installing multiple layers may be technically fine. The old shingles probably lost as much weight, evaporated oil, and washed away granules as the new metal material will add. However, going over multiple layers can become an issue: Most building codes allow for only 2 layers of roofing on a home. If a future buyer or mortgage company inspects your home, more than 2 roofing layers could be considered a problem and may require remediation.

Don’t let these reasons not to roof over deter you. There are plenty of instances where roofing over asphalt shingles makes sense.

When does it make sense to install metal on top of asphalt shingles?

If there is no existing weight problem, active leaks, or decking in bad condition, metal roofs can be installed over shingles with appropriate underlayment.

Leaving the asphalt shingles in place has positive benefits:

  • Increases the building’s thermal mass for energy efficiency
  • Avoids having to dump old roofing materials in landfills
  • Reduces the risk of debris damage during the re-roofing process
  • Allows homeowners to spend money on an upgraded roof rather than on removing and disposing of their old one

Our metal roofing can be very advantageous in terms of allowing a new roof to be installed over existing shingles.

Roof Over or Do Over?  Ask Us.

The best way to find out if your home is a candidate for leaving the existing shingles in place as we install a new metal roof is to contact us for a free roofing consultation.

We’re your local professional metal roofing contractor. We have the experience and expertise to guide you to a great roofing solution. With a pressure-free roofing consultation, we will thoroughly assess your current roof and provide a plan for installing on top of your existing shingles or completely redoing your roof.

  • Our factory-trained teams install your new metal roof in accordance with manufacturer recommendations.
  • Receive our industry-leading product and installation warranties to ensure the performance of your roof for a lifetime.
  • We’ll send you a list of references and drive-by opportunities in your area so you can experience McCarthy Quality firsthand.

So please don’t wait! Contact us today for answers to your questions or a FREE roofing consultation and get started on making a roofing decision that’s good for the earth and your wallet.