#39 – Metal Roof Installation: Should Shingles be Removed?
Should Shingles be Removed Before Installing a Metal Roof?
If your home is presently roofed with asphalt shingles, you may be able to avoid the expense of tear-off and protect the environment by reducing landfill.
Metal roofs are much lower weight than most other roofing materials. Aluminum roofing weighs around 50 pounds per 100 square feet and most steel roofs are 80 – 100 pounds. Traditional shingles for that same size area are 275 – 425 pounds in comparison. This encourages the installation of metal roofs over existing roofing. Additionally, most building codes allow for two layers of roofing to be on a home.
Unlike asphalt, installing a metal roof as the second layer should not impact the warranty on the second layer. Doing so often voids the warranty on the second layer of asphalt shingles. Now, if a roof has current issues such as leaks or deteriorated decking including dips and buckles, those must and should be addressed before the new roof is installed, and that may require removing the old shingles.
Regardless of whether the old roof is removed, a layer of underlayment should be installed prior to any metal roof installation. Always make sure, too, that your roof is installed in accordance with manufacturer recommendations. Leaving the old shingles in place has several positive benefits. It increases the building’s thermal mass for energy efficiency. It avoids having to dump old roofing materials in landfills. It reduces the risk of interior or landscaping damage during the re-roofing process. And it allows the homeowners to spend their money on an upgraded roof rather than on removing and disposing of their old roof.