What causes roof shingles to curl up at corners?

Thursday, June 14, 2018

Usually A Sign of Age

Shingles curl as they reach the end of their serviceable lifespan. It’s one of several signs of that an older roof is approaching time for replacement. Other indications are  areas of missing surface granules and loose tab adhesion, which makes the front of the shingle lift easily. The photo above shows the first stage of curl, while the one below is an example of more advanced curl.


Three Reasons For Premature Shingle Curl

    Curl can also happen prematurely on a newer roof. Three reasons for premature curl are:

  1. Poor attic ventilation - Roofs get hotter and have excessive moisture rising up under the sheathing when there is inadequate air flow. It should come in through the soffit and and rise out of vents at the ridge of a roof. The overheating speeds up normal deterioration of the shingles.

  2. Multiple roof layers - The building code allows a second layer of shingles to be laid over the original one—but no more than two total layers. This eliminates the labor and dump fees for removal of an older roof, but speeds up the deterioration of the new one. The new roof gets laid over an uneven surface, nailing through the old shingles is less secure, and the original roof continues to age and move under the new one. So early curl is more likely. See our blog post How can I tell if a roof has more than one layer of shingles? for more on this.

  3. Sloppy installation - If the shingles are not secured with enough nails, the nails located poorly, or the shingles are not aligned accurately, early curl can occur.

    Unfortunately, premature curl can become an issue when you apply for a new homeowner’s insurance policy. For an overview of the signs that your roof is ready to be replaced, see our blog post How can I tell if the house needs a new roof?

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  To learn more about roofs and attics, see these other blog posts:

Why is my roof sheathing sagging between the trusses?

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

What are the mistakes to avoid when doing attic improvements?

What causes shingles to buckle along a line on the roof?

What causes leaks at a fake roof dormer? 

What causes a sagging roof ridge line?

What causes bubble-like blisters in a built-up and gravel roof?  

Why does it cost so much more to replace a steep roof than a low slope roof? 

What is "ponding" on a flat roof?

Is an attic required to have a light by the building code? 

How can I inspect my roof for hurricane damage?

Why is premature curl of roof shingles a problem?

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

What are the common problems with attic insulation? 

What is the life expectancy of an asbestos cement shingle roof? 

What's the average lifespan of a roof?

Why is it a mistake to replace a roof and not replace its flashings? 

Why is there no attic access hatch in the house?

What is the building code requirement for an attic access hatch, scuttle, or door? 

Does a roof with multiple layers of shingles last longer?

What can I do to prevent roof leaks?

Are roof trusses better than roof rafters (stick framing)? 

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

What are the most common problems with wood roof trusses?

What causes a lump or dip in the roof? 

If my roof is not leaking, why does it need to be replaced?

How can I be sure my roofing contractor got a permit?

How many layers of roofing are allowed on a home? 

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

Can metal roofing be used on a low slope/pitch roof? 

How can I make my roof last longer?  

What are the warning signs of a dangerous attic pull-down ladder?

How can I find out the age of a roof? 

Should I buy a house that needs a new roof?

Should I buy a house with an old roof? 

What are those metal boxes on the roof?

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

Why do roof edges start leaking?

Why do my dormer windows leak? 

Do home inspectors go on the roof? Do they get in the attic?

Should I put gutters on the house? 

How much of a roof truss can I cut out to make a storage platform in the attic? 

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

What does a home inspector look for when examining a roof? 

Do stains on the ceiling mean the roof is leaking?

How can I tell if the house needs a new roof?  

 Why does my homeowner's insurance want a roof inspection?

What are the hazards to avoid when going into an attic? 

     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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