Installing a Standing Seam Metal Roof Over Shingles

Did you know there is a quick and efficient method for installing standing seam metal roofing directly over asphalt shingles, without a tear-off? Well there is one!

If you are looking for a quick and efficient method to install standing seam metal roofing directly over your existing asphalt shingles, we can help! McElroy Metal has the perfect solution with our innovative 138T Symmetrical Standing Seam Panel, designed to simplify the recover process while offering superior performance and energy savings.

Beyond energy savings, it’s also good for the environment. “Shingle tear-off is one of the biggest sources of construction debris that is responsible for clogging our landfills,” says Charlie Smith, National Recover Manager at McElroy Metal. “So the idea of leaving shingles in place makes a lot of sense.”

Metal Roof Options for Over-Shingle Applications

McElroy Metal’s Residential Standing Seam Recover System

Our top shingle recover system is designed around McElroy Metal's 138T symmetrical standing seam panel. Featuring 1-3/8 inches tall seams, the 138T is a two-piece mechanically seamed metal roofing system.

Symmetrical Panels

“We designed the shingle recover system around 138T because we believe symmetrical panels are the best roofing systems on the market today,” Smith says. “They have the most watertight seam design, they get unmatched wind uplift resistance and they are easy to fix if there is ever a problem. The 138T is perfect for shingle recover applications where we are working on a solid deck and the slope is 2:12 or greater. For the installer using a symmetrical panel, there is much less scrap and he has a lot more flexibility on how he installs the roof.”

Beyond being installer-friendly, the system also offers other efficiencies.

Integrated ¾” Air Space

“Since we wanted to eliminate the expense of a roof underlayment, we needed to get the panel up above the shingles to eliminate the chance of abrasion,” Smith says. “We found that 3/4-inch is the perfect height. We’ve designed our clip so it holds the panel up where it does not touch the deck, yet still allows you to walk on the roof without damaging the clips or panels.”

This 3/4" air space has another benefit. When combined with vented eave and ridge material, it creates uninterrupted air flow between the two roofs, dramatically decreasing attic temperatures and subsequently reducing cooling expenses.

Energy Savings with Above Sheathing Ventilation (ASV)

Known as “above sheathing ventilation,” or ASV, this idea uses airspace to help reduce heat transfer. Testing at Oak Ridge National Laboratories (Tennessee) demonstrated how a free-flowing airspace between a metal roof and shingles can reduce heat transfer by up to 30 percent. Reducing heat transfer greatly reduces cooling costs, a savings for the building owner. During the winter months in colder climates, insulating airspace will also reduce the chance of ice buildup caused by heat transfer up through the roof. Watch this video to learn more.

McElroy Metal’s 138T system utilizes 3/4-inch deep corrugated metal under the panels at the ridge, hip, and headwall locations to support the panel, providing free airflow and a surface for closure attachment.

“Our idea is to take the tear-off and roof underlayment money and roll it into the new roof system,” Smith says. “Then help the owner pay for it by long-term energy savings provided by the above sheathing ventilation. There are millions of squares of shingles on schools, municipal, military, commercial, and, of course, residential buildings out there, and it’s time to recover them with metal!”

Exposed Fastened Metal Roofing Options

While standing seam systems, like our 138T, offer the best performance, exposed fastened panels can also be an option when budget is the primary consideration. As the name implies, exposed fastened systems use a visible screw to attach the panels to the substructure. When properly installed and on shorter panel runs, life expectancy can be similar to standing seam systems; however, incorrect fastener installation and worn-out seals around the fasteners can lead to leaks. To learn more, check out 8 faqs for Installing Exposed Fastener Metal Roofs.

Metal Roofing Benefits Over Asphalt Shingles

Life Expectancy & Overall Cost

Metal roofing offers a 50-60 life expectancy which is 2-3 times greater than what shingles offer. So while metal roofing may cost more initially, when you consider multiple shingle replacements during ownership, metal roofing actually ends up being the less expensive roof in the long term.

Durability

Metal roofing is more resistant to extreme winds, hail, and fire than asphalt shingles. Consequently, many insurance companies offer discounts for metal roofing.

Maintenance

Depending on the environment, asphalt shingles can be prone to curling, mold growth, blow-off, replacement after storms, and granular loss. In contrast, metal roofing requires minimal maintenance. Most manufacturers recommend only an annual inspection around flashings and the occasional power wash for their metal roof customers.

Energy Efficiency

For your cost-conscious customers, it’s also important to remember that properly designed and installed metal roofing systems can reduce energy bills by 20-40%. Reflective paint properties and light colors help maximize the savings.

Recyclability

For building owners interested in environmentally friendly options, metal roofing is 100% recyclable at the end of its service life. That means their old car could be their new metal roof. In contrast, worn-out asphalt shingle roofs likely end up in landfills contributing to our ever-growing trash problem. Metal roofs are one of the most eco-friendly options available!

Reduced Construction Cost & Debris

Beyond recyclability, leaving the existing shingles in place also eliminates the cost of tear-off and disposal for the original shingle roof. Further, avoiding shingle tear-offs significantly reduces landfill waste.

Challenges and Solutions for Shingle Recover

Clip Alignment

When installing a metal roof directly over shingles with no underlayment, several challenges must be overcome. The main issues are clip alignment and abrasion on the underside of panels. Smith says the key to the shingle recover system is the patented 138T Shingle Recover Clip.

One clip is long enough to sit on two shingles, aligning it into the plane of the roof. Clip alignment is key to the proper installation of 138T standing seam panels. The clips have eight holes so the installer can align the fasteners through the ends of the shingle tabs. The clip will also work on dimensional or architectural shingled roofs.

Existing Shingle/Deck Condition

It’s important to realize that steel can often act like a mirror and telegraph deck and shingle inconsistencies through the new steel panel. Consequently, when considering recover applications, it’s important that existing shingles lay flat (aren’t curled) or missing. The existing deck should also be inspected to ensure adequate structural support for the new roofing system.