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Can one missing or damaged shingle cause a roof leak?
Friday, November 11, 2022
Although possible that a single missing or damaged roof shingle can cause a roof leak, it’s unlikely unless you can see exposed roofing felt or wood sheathing. But damage in just one spot is like a small hole in a your favorite sweater. Both are made of interwoven pieces that, if not repaired promptly, will eventually unravel and rip open.
The good news is that there’s part of another shingle under the missing or damaged one, and a sheet of roofing felt below it. They provide two backup layers of leak protection.
But it is only a temporary reprieve. The shingle below can leak at the non-downlapped sides, and a missing shingle exposes nails that become leakage points. Also, the roofing felt below the shingles is not intended to be left exposed to sun and weather. It deteriorates quickly, eventually cracking and exposing the roof sheathing, which allows water to migrate under the roofing assembly around it.
A roof shingle snapping off is more likely to happen at an older roof. It starts when the leading edge of the shingle loses adhesion and flaps up in the wind. A shingle gets brittle as it ages, so it snaps just below the overlap of the shingle above it in a gust of wind. Then an adjacent shingle or two usually also break off later.
A roof leak nearby, possibly around a plumbing boot roof penetration, can be another cause of a missing or loose shingle. The leak runs down the slope under the roofing and rots the wood sheathing in its path, causing a shingle or two to come loose.
A missing 3-tab shingle above the seam between two shingles below it can also start to leak. Sloppy shingle nailing, impact damage, or defective manufacture are other potential culprits. But, whatever may have caused it, prompt repair of a single damaged or missing shingle will head off more extensive repairs in the future. Also see What are common problems of asphalt shingle roofs? and Why is my roof leaking?
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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
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