How To Look At A House
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What are common problems of asphalt shingle roofs?
Tuesday, July 5, 2022
Asphalt composition shingles are the most popular roofing material in America. More than 75% of homes are topped with them. Shingles are relatively inexpensive, simple to install, durable, and the premium architectural shingles have good curb appeal. But, like any roof material, problems can develop due to age, poor installation, manufacturing defects, or severe weather.
Granule Loss - This can occur prematurely in the first decade of the life of roof, but it is also normal for shingles to gradually lose granules as they age. So it is one of the signs that help an inspector to determine the approximate age of a roof. The granules are there to protect the surface of the shingle from damage caused by the sun’s UV-rays and, once they are gone, the deterioration of the roof surface speeds up. See our article Why is granule loss a problem for an asphalt shingle roof? to learn more.
Curling Edges - Shingles curl as they reach the end of their serviceable lifespan. It’s another sign that an older roof is approaching time for replacement, and is usually coupled with poor tab adhesion. But sometimes shingles begin to curl prematurely and, even if the tab adhesion is still good, many insurance companies consider it a sign that the roof needs to be replaced. Go to What causes roof shingles to curl up at corners? and Why is premature curl of roof shingles a problem? for more on this.
Loss of Tab Adhesion - Shingles have adhesive tabs on the bottom surface that hold the lower edge to the top surface of the shingle below. When shingles are beginning to lose adhesion, that edge can be lifted up by hand and it makes a soft tearing sound. As they totally lose adhesion, lifting makes no sound at all. Checking tab adhesion is another way that a home inspector evaluates the condition of a shingle roof. The adhesive tabs are heat-activated and require several warm days after installation to take hold. Sometimes a manufacturing or installation defect keeps the shingles from setting properly. Our article What would cause a new asphalt shingle roof to have loose tab adhesion (sealant strips)? has more details on this defect. Also, dark lines running parallel to the shingle strips indicate loose tabs that are flipping up in the wind, and the line is a crease where the shingle has hinged up before falling back down. Eventually it will snap off at that line.
Popped Nails - A popped nail looks like a wrinkle in a line of shingles when you look up the roof from the ground. Nails lifting and eventually popping through a shingle roof covering can cause small leaks and it eventually leads to rotted roof sheathing over time if they are not repaired. For the full story, go to Why is a popped nail in a shingle roof a problem? How do I fix it?
Pitting or Pockmarks - Roofers call them “blisters.” They usually occur during the first couple of years after roof installation, and are caused by excessive heat under the shingles due to poor ventilation of the attic, which is a common problem in Florida. The heat expands any volatile gasses or moisture trapped in the layers of asphalt during manufacture, which try to escape and form tiny raised blisters in the roof surface. Eventually each blister pops, knocking off the granules above it, then the blister recedes back in place to become the pitted spots you see in the roof shingles.
Extensive blistering is rare, but could lead to a shortened lifespan of the roof due to the missing areas of granules if widespread across roof. Blistering should not be confused with hail damage, which makes a shallow bowl-shaped indention in the roof with the granules still mostly intact in the area of damage.
Roof Pitch Too Low - Roofs with a slope below the code minimum of 2/12 pitch are prone to leakage from wind-blown rain or simply a heavy rain. We see this problem in mid-20th century houses that formerly had a tar and gravel roof on a shallow slope and also at saddles at a dead valley. See our articles What is the minimum pitch/slope of an asphalt shingle roof? and What is a dead valley at a roof? for more on both issues
Failed Flashings - Flashings protect the roof at the places where it is most likely to leak: around the edges and roof penetrations. They can fail due to poor installation or inadequate repairs, but the problem is usually old flashings that were not replaced when a new roof was put on. See our article Why is it a mistake to replace a roof and not replace its flashings? for more on this.
Damaged or Missing Shingles - A missing shingle exposes the nails securing the shingle below that it overlaps, and exposed nails will eventually leak. Shingles begin to get brittle as they age and, when the wind gets under the edge, it can snap off pieces of the shingle.
Leaking - A leaking roof is a symptom of one or more roof defects. See our article Why is my roof leaking? for what to look for when water is coming through the roof. Also, what appears to be a roof leak might not be. Go to Do stains on the ceiling mean the roof is leaking? for other possible causes of water intrusion.
Temporary Repairs - Mastic slathered over a roof leak is a quick way to temporarily stop a leak. But it's not a permanent fix, which requires removing shingles in the area of the problem and weaving-in new ones.
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To learn more about roofs, see these other articles:
• Can I put a new asphalt shingle roof over an existing shingle roof on a manufactured/mobile home?
• Can one missing or damaged shingle cause a roof leak?
• How can I tell if a roof has more than one layer of shingles?
• What is the average lifespan of an architectural (dimensional) shingle roof?
• What is the average lifespan of a regular (3-tab) 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?
• 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 things can void a shingle roof warranty?
• Can water run uphill on a roof?
Visit our ROOF AND ATTIC page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.
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