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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Here’s links to a collection of some of our other articles about SHINGLE ROOFS:

• Why is granule loss a problem for an asphalt shingle roof? 

• What causes roof shingles to curl up at corners?  

• Why is premature curl of roof shingles a problem?

• Can I put a new asphalt shingle roof over an existing shingle roof on a manufactured/mobile home?  

• How can I tell if a roof has more than one layer of shingles?  

• Does a roof with multiple layers of shingles last longer? 

• Why is a popped nail in a shingle roof a problem? How do I fix it?

• What are the dark lines running parallel to shingles on my roof?

• What is the average lifespan of an architectural (dimensional) shingle roof? 

• What is the average lifespan of a regular (3-tab) shingle roof?

• What does "lack of tab adhesion" in an asphalt shingle roof mean?

• What is the minimum pitch/slope of an asphalt shingle roof?

• What's the difference between an "architectural" and a regular shingle roof? 

• Why is an asphalt shingle roof difficult to inspect when wet right after it has rained?

• How can I tell if an asphalt shingle roof manufacturer's warranty rating is 20 years, 30 years, or more?

• What causes small areas of pitting or pockmarks in an asphalt shingle roof? 

• Why are there sometimes damaged shingles around an area of roof shingle repair or the tie-in of a new roof?

• What would cause a new asphalt shingle roof to have loose tab adhesion (sealant strips)? 

• Can I install a new metal roof over an asphalt shingle roof?

• Are asphalt shingles slippery when wet? 

• Do asphalt shingles need time to settle and adhere?

• What is granular loss on a shingle roof? 

• What things can void a shingle roof warranty?

• Can water run uphill on a roof?

• What is a dead valley at a roof?