Inside Common Roofing Issues

The Questions Home Inspectors Need to Ask and Some of the Most Common Problems They Should Look For

July 1, 2021

While the most popular roofing material has not changed (hello, asphalt shingles), other types of roofing are seeing growth in some areas of the country. We talked to Maciek Rupar, technical services director for the National Roofing Contractors Association, about different types of roofing materials, and what home inspectors should look for.

Metal Roofing

According to Rupar, the areas in the country where metal roofing is taking more of the market are often those that experience more severe weather, especially as metal is often marketed as being more impact-resistant than shingles. But, of course, not all roofing materials are created equal. Metal requires more skill from installers, Rupar said.
“The work tends to be more involved. You need more skill and more tools. You have to invest more time and training in order to be able to do it well,” he said.

Metal roofs have undergone a resurgence of popularity. A recent roofing study from The Freedonia Group found that the U.S. demand for metal roofing is expected to rise 2.7% per year in 2023. For residential roofing, the study claims this above-average rate of growth will be due in part to homeowners’ interest in installing metal roofing to create a more unique exterior appearance than asphalt shingles.

When you’re working with metal roofing, you’re typically working with either roll-formed panels such as standing seam metal roofing or stamped metal shingles. Sheffield Metals defines standing seam metal roofing as a concealed fastener metal panel system that features vertical legs and a broad, flat area between the two legs, commonly called the pan. Standing-seam metal roof panels are seamed at the vertical legs above the pan where water runs off. Standing seam systems are secured with concealed fasteners; the panel may be attached to the roof deck using fixed or expansion clips or directly fastened to the deck under the vertical leg (fastener flange).

Sheffield Metals goes on to define stamped metal shingles as smaller modular panels that are stamped or pressed to resemble the look of shingles, shake, tile, and slate roofing. Stamped metal roofing often utilizes a four-way interlocking system at all sides of the panel, which is then installed in staggered courses. Most stamped roofing is made from pre-painted PVDF-coated steel and aluminum.

“We like to see standing seam metal panels attached with fasteners that don’t penetrate through the actual panel that’s exposed to the weather,” Rupar said, “So that they would be attached with clips that allow them both to move and keep water on the surface of the panel away from any holes.”

Looking for Holes and Leaks

While Rupar said clips allow the metal to move freely on the roof, the metal will still expand and contract with changes in temperature. “You don’t want to install large sheets of metal—such as metal panels—where they will be pinned in place in more than one location along the length because that will bind the metal when it expands enough to be basically bent out of shape.”

Clips are designed to allow some movement in the panels when they’re joined together on the roof. The clips are inserted in seams so the metal can basically slide along the length of the roof slope, Rupar said.

That differs from another metal roofing material. “If you attach a panel with a penetrating fastener, that fastener penetrating the panel creates a stress point on the panel. If the panel is attached this way in more than one place and there’s an appreciable amount of material between those two attachment points and temperature changes over a large range, that metal is restricted in its ability to accommodate its dimensional change.”

That, he said, tends to put stress on the fasteners and sometimes the holes that those fasteners penetrate will expand. “Even though they are supplied with gaskets, those holes will sometimes get so large that they may allow leaks.”

It takes a skilled hand to fasten panels so gaskets are correctly compressed and not cut or damaged in the process. In a through-fastened system, Rupar said inspectors should look for fasteners under stress, as they may cause holes to expand or enlarge as panels push against the fastener. “You may see fasteners that are moved out of their original location, whereas with clip-fastened panels you don’t see the fasteners at all. They are all hidden underneath.”

With a clip-fastened system, Rupar advises home inspectors to look at the flashings, or the pieces of metal shaped to cover any transitions or places where the roof system interfaces with features on the roof, like dormers or any penetrations through the roof. “Typically flashings or those transitions are where failures happen with roofing,” he said. “This isn’t just limited to metal panels. It’s really all types of roof coverings. A roof inspection will typically focus on flashing first.”

Solar Panels

As for other roofing trends across the U.S., Rupar said there’s an uptick in PV panels in the market in areas where homeowners see a higher return on investment. While Rupar advises solar panels be installed while reroofing rather than trying to retrofit an existing roof, there are many cases where homeowners try to make their old roof work.

Here, too, inspectors should look at the flashings first—especially at whether they were correctly installed to weatherproof all penetrations through the roof. “When installing a rooftop PV system over an existing roof system the numerous penetrations that have to be added are challenging to flash correctly.”

Green Roofs

While you can’t—or probably shouldn’t—expect to install a green roof on a steep slope roof, homeowners with a low sloped roof, concrete construction, or an occupiable rooftop deck may have a green roof, Rupar said. Green roofs must take into consideration the added weight the roof must bear. “Many people may not realize that when you design a vegetative or green roof you must design the structural capacity of the structure based upon the fully water-saturated overburden—and that includes the plants, the growing medium, and any waterproofing membrane, or essentially the roof in this case. You’re talking about an amount of weight that can be quite considerable.”

Once you confirm that the structure can actually support the full weight, Rupar said home inspectors should verify that the work was done using both materials and techniques used in waterproofing. “This is different from roofing,” he said.

“A typical roof is not expected to withstand standing water. We call that hydrostatic pressure. With green roofs, because you have the potential of the growing medium retaining a lot of this water, you have hydrostatic pressure, so the same application techniques and some of the same materials used for roofing will not work.”

Don’t Forget

Proper attic ventilation is another huge issue when it comes to roofing inspections.

Rupar said the first thing home inspectors should ask when inspecting this area of the roof is whether the attic was ventilated for the right reason. “The primary reason we ventilate attics with outside air is to keep the roof deck temperature below freezing during winter months in cold climates to prevent the melting of snow and refreezing along the eaves,” he said.

Leaks from water backing up behind ice dams are a recurring problem in cold-climate areas that receive significant snowfall. “This is primarily why you would ventilate,” Rupar said. “But a better way to prevent issues with ice damming is to make sure your ceiling is airtight. This may be something to look at.”

Look for air leakage or air exchange between the top floor of a house and the attic space, if unconditioned. “Look at whether weatherstripping is properly installed in the roof hatch, if there is one,” Rupar said. “If there are any openings in the ceiling, such as can lights, make sure those are properly sealed.” Tree debris plugging exhaust vents is another problem to watch out for.

Read more about NRCA’s roofing guidelines in the newly updated 2021 roofing manual for steep-slope roof systems. The guide was recently updated to align better with recommendations from the Tile Roofing Institute. Find out more at nrca.net.

The opinions expressed in this article are those of the author only and do not necessarily reflect the opinions or views of ASHI. The information contained in the article is general and readers should always independently verify for accuracy, completeness, and reliability.


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