Small commercial building owners and homeowners across the country are choosing the cost-effective and sustainable option of retrofitting their existing roofs with metal
Retrofitting (or re-roofing) a roof vs. total replacement is the process of installing a new roofing system over the existing roof.
A Dodge Report released in September found that metal roofing used for residential re-roofing in the U.S. rose from 12 percent in 2019 to 15 percent in 2020, driven in part by the need for stronger protection against climate extremes and a greater demand for sustainable and low maintenance options.
“There’s no doubt homeowners are getting the message: Durable, stronger and longer-lasting quality materials are a much better investment for your home over the long run, especially in light of climate extremes,” said Renee Ramey, executive director of the Metal Roofing Alliance (MRA). “That mindset is reflected in the latest numbers and overall growth of the metal roofing industry.”
Retrofitting Your Roof vs. Total Replacement
No matter what type of material you use for your home or commercial building, there will come a time when the roof needs replacing.
The National Association of Home Builders and Bank of America Home Equity combined to release the “Study of Life Expectancy of Home Components” which found that “the life of a roof depends on local weather conditions, proper building and design, material quality, and adequate maintenance”.
The study estimated life expectancy of different roofing materials:
- Slate, copper, and clay/concrete roofs have the longest life expectancy – over 50 years
- Roofs made of wood shakes can be expected to last for about 30 years
- Roofs made of fiber cement shingles have a life expectancy of about 25 years
- Roofs made of asphalt shingles last for about 20 years
Copper is considered the longest-last type of metal roofing there are many options including zinc with State Farm estimating that the average metal roof will last 40 to 70 years.
The Dodge Report also revealed that “while traditional metal roofing styles such as standing seam remain popular, homeowners also are gravitating to the wide variety of designs that metal roofing offers, including shingle, shake, tile and slate.”
The question then becomes, when it is time to replace your aging roof, should you start from scratch and install an entirely new roof or can you retrofit over your existing roof?
“It is a fair question considering labor removal costs and that obsolete roofing materials contribute 9 to 10 million tons of waste to landfills every year,” says the Metal Construction Association (MCA) .
New Metal Roof Systems Made for Retrofitting
Retrofitting over your existing roof – especially laying another layer of shingles over the current layer -- has traditionally posed some thorny issues such as adding too much weight to the structural design of the deck or roof framing.
“Installation of a new metal retrofit roof system over an old roof is an entirely different scenario,” says the MCA white paper “Retrofitting Existing Roofing with Metal”. “Such systems were specifically created for this purpose.”
The white paper says that the advantages of metal retrofit systems includes:
Weight and Labor Savings
- Metal roofs are low weight, ranging from 40 to 140 pounds per “square” (100 square feet). This stands in stark contrast to virtually all other roofing materials which can be as heavy as 250 pounds per square or more. That difference could allow for the weight of a metal roof in the design when a second layer of conventional roofing is not an option. This is especially important for aging structures or in areas with high earthquake loads.
- The cost of construction labor, coupled with shortages of the same, encourages property owners to invest in premium roofing systems rather than labor to remove old roofing materials.
- Leaving the old roofing material in place provides a small R-value boost to the building envelope to enhance energy efficiency if metal sub-purlins or battens are used.
Enhance Appearance and Durability
- Long-life durability - Many metal roofing products carry warranties of 20-50 years and MCA studies have shown a 60-year service life for a properly constructed metal roofing system.
- Resiliency and high performance for high wind applications, fire resistance, and impact protection not available from other materials.
- Attractive curb appeal with styles including raised vertical seam and ribbed profiles as well as “modular” panels with the aesthetics of shingles, wood shakes, slate, or tile. Coatings include a wide range of high-performance and heat-reflective paint systems as well as granulated finishes.
While not measured by the Dodge Report, the MRA theorizes that homeowners are increasingly attracted to metal roofing’s low maintenance and easy-care benefits, based on the organization’s own data and web site that receives hundreds of thousands of visits from homeowners looking to learn more about metal roofing every year.