#39 – Metal Roof Installation: Should Shingles be Removed?

May 3, 2017 | Filed under: Metal Roofing 101 Series, Roofing Help Videos, Roofing Installation

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.

3 responses to “#39 – Metal Roof Installation: Should Shingles be Removed?”

  1. […] you consider what type of roof is best for your home, one consideration will be whether the old roof needs to be removed, or not. In some cases, based on the type of roof it is and the type of roof you’re installing, it may be […]

  2. wayne mallette says:

    How is the sweeting and condensation controled? I live in north Florida and on a cloudy or rainy day water can drip close to noon, or longer just from the humidity.

    • toddmiller says:

      There will likely be dew on the outside of the roof. Condensation occurs of course when warm moist air reaches a cold surface. If warm moist air inside your home reaches the roofing system and it’s cool enough that dew point is reached, then condensation will occur someplace below the surface of the roof. Controlling condensation inside the living space or attic space is done through a combination of vapor barrier behind the drywall, insulation (often on top of the ceilings), and ventilation (in the attic). You can sometimes get by with just two of those three things but usually not with just one or less. I am always happy to help guide folks through condensation concerns or problems. Just email me at todd@asktoddmiller.com

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