Do Metal Roofs Leak More Than Shingles?

Do metal roofs leak more than asphalt shingles?

No, a properly installed metal roof does not leak more than asphalt shingles. The idea that metal roofs leak comes mostly from exposed-fastener panels on barns and sheds, where hundreds of screws go straight through the face of the metal and depend on rubber washers to stay sealed. As those washers age, they can let water in. Interlocking aluminum shingles work differently. The fasteners go through the top flange of each panel and are covered by the next course, so they never see rain. The joints are formed metal channels that turn water back down the slope. Under the panels, an underlayment provides a second barrier. With correct flashing, an interlocking metal roof is a very watertight roof, including in the wind-driven rain of a New England nor'easter.

Where do roof leaks actually come from?

Roof leaks almost always come from places where the roof surface is interrupted, not from the open field of the roof. That is true for asphalt, slate, wood and metal. The usual suspects are chimneys, where the roof meets masonry on four sides; skylights, whose curbs need flashing that is integrated with the courses around them; valleys, where two roof planes concentrate water; sidewalls and dormer cheeks, where step flashing meets siding; and plumbing vents and exhaust pipes. Older New England homes tend to have plenty of all of these. A Victorian with turrets and dormers or a farmhouse with additions from several eras has far more detail work than a simple gable roof, and that is where installation skill shows.

How does flashing work on an interlocking metal roof?

Flashing on an interlocking metal roof is formed metal that directs water around anything that breaks the roof plane. At a chimney, pieces are fitted along the sides and front, with a back pan or cricket behind the chimney on the uphill side to split the water. At a wall, the flashing turns up behind the siding so water can't run behind it. In a valley, a formed channel carries the combined runoff of two slopes. On an interlocking system the flashing is designed to work with the panel locks so water is always moving on top of the metal and downhill. This is detailed work done on site, which is why Interlock® roofs in New England are installed only by our trained crews rather than by whoever buys the panels.

Are ice dams a roof leak?

Ice dams cause water to come in, but they are not a failure of the roofing material, and ice damming is excluded from the Interlock® material warranty. An ice dam forms when warm air leaking into the attic melts snow on the upper roof. The water runs down to the cold overhang, refreezes, and builds a ridge of ice that traps more water behind it. That water can back up under any roof covering. The solution is in the house: sealing air leaks into the attic, adding insulation, and balancing intake and exhaust ventilation so the roof deck stays cold. A metal surface may shed snow differently than asphalt, but no roof prevents ice dams on its own. We look at your attic, eaves and ventilation with you so the new roof isn't blamed for a heat problem.

Could it be condensation instead of a leak?

Sometimes what looks like a roof leak is condensation in the attic. In a New England winter, warm, moist air from bathrooms, kitchens and the living space can rise into a cold attic. When it meets the cold underside of the roof deck or nails, it condenses and can drip or frost over, then melt on the next mild day. The signs are frost on nail tips, damp spots spread across the sheathing rather than concentrated under one feature, and dripping that shows up on cold mornings without any rain. The fixes are air sealing, making sure bath and kitchen fans vent outdoors rather than into the attic, and adequate ventilation. It is worth checking before assuming the roofing is at fault.

What should you do if your metal roof leaks?

If your roof leaks, note when it happens and where the water appears, then call the company that installed the roof. Whether the drip shows up during wind-driven rain, after a thaw, or only on cold mornings tells the installer a lot about the cause. Don't climb on the roof or try to seal joints yourself; walking on interlocking panels or forcing caulk into the locks can create new problems. Keep your warranty documents handy. For Interlock® roofs we installed, contact our existing-customer service team. The Guardian Lifetime Limited Material Warranty covers material and finish for the original purchaser while they own the home, each subject to its own terms and exclusions.

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