In the U.S. and Canada, homeowners are gearing up for spring and summer exterior home improvement projects, including re-roofing their homes.

This is also a time when a massive amount of waste is created, due to the removal and disposal of old asphalt roof shingles. As the most common type of roofing material, approximately 11 million tons of worn-out asphalt shingle roofing waste is dumped into the landfill every year, representing a whopping eight percent of the total building-related waste stream in the United States.

To help reduce the environmental impact and save on re-roofing labor costs, experts say the fact is an old asphalt roof doesn’t necessarily have to be torn off and removed in order to install a new roof. Thanks to its lighter weight, metal is one of the only roofing materials that can be installed directly over asphalt. The benefits of doing so not only include preventing waste, but realizing the savings that comes from reduced labor and tear-off costs and increased long-term energy efficiency.

According to the Metal Roofing Alliance (MRA), the leading nonprofit trade organization representing the industry, it’s the lower weight and greater resiliency of metal roofing material (50 lbs. per 100 square feet for aluminum and 80-100 lbs. for steel, as compared to nearly 275-425 lbs. per 100 square feet for asphalt) that makes it suitable for installing over asphalt without adding too much weight for a home’s structure. It also increases insulation properties, helping homeowners save on heating and cooling costs.

“Every year, we receive questions from homeowners who are rightly concerned about all the waste and mess that comes from removing their old asphalt roofs, asking if they can install longer lasting metal over their existing roofs to help reduce waste and avoid having to re-roof again in the future,” said Renee Ramey, MRA executive director. “In many cases, the answer is yes, and there are plenty of great reasons for doing so.”

Warranties offered on quality metal roofing systems installed over asphalt shingles are not typically impacted as long as the roof is properly installed, which is not the case when it comes to installing a second layer of asphalt over the top of an old shingle roof. That’s because heat gain can impact the integrity of asphalt shingles and cause the new second layer of roofing to deteriorate much faster, while high temperatures will not impact quality metal roofing systems or finishes.

Other factors and considerations for installing a new metal roof over asphalt include:

  • Layer limits: Most building codes allow for only two layers of roofing. Metal can typically be installed directly over a single layer asphalt roof, but tear off may be necessary for roofs that have more layers.
  • Structure soundness: If the old asphalt roof is severely damaged and has leaks, deteriorating decking or buckling, complete removal may be unavoidable before a new roof can be installed.
  • Underlayment essentials: The proper underlayment should always be used for installing a new metal roof, including over an old asphalt roof. Use the recommended underlayment in accordance with the manufacturer’s instructions to help protect your new metal roof.
  • Pro perspective: For any roofing project, work with an experienced, qualified installer who uses quality materials and proper installation methods. Get recommendations and make sure they are members of organizations such as the MRA and other trade groups that advocate for industry quality standards.
  • Above and beyond benefits: Because quality metal roofs last much longer, are more durable and energy efficient and can be 100% recycled at the end of their long lives, the sustainability and savings benefits are multiplied by installing It directly over an old asphalt roof. By saving on removal and tear-off, homeowners also can increase their value by applying that savings to upgrading their roof quality to ensure long-term reliability and performance, low-maintenance and increased protection.

“For a homeowner, leaving their old shingles in place can actually make the home more energy efficient and resilient,” said Todd Miller, president of Isaiah Industries, an MRA member and well-known industry expert. “But perhaps more importantly, it means they can use the money they save on old roof removal and disposal to invest in an upgraded metal roof for their home. Sometimes, those savings allow them to buy the better roof they really want.”

About Metal Roofing Alliance (MRA)

Representing metal roofing manufacturers in the United States and Canada, the Metal Roofing Alliance (MRA) was formed to help educate consumers about the many benefits of metal roofs. The main objective of MRA is to increase awareness of the beauty, durability and money-saving advantages of quality metal roofs among homeowners, as well as to provide support for metal roofing businesses and contractors. For more information, visit MRA.