How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
What are the dark lines running parallel to shingles on my roof?
Saturday, August 4, 2018
If it looks like the photo above, then your shingle roof has lost its tab adhesion at the leading edge and is flapping up in high winds. The dark line is a crease created when the shingles repeatedly hinge up under wind pressure.
Shown below is a wider view of a roof with this problem, along with an example of a broken shingle that you will find blown up the roof or laying on the ground after they start to snap at that hinge line.
Another sign of this problem is leaf debris trapped under the shingle.
Also, see our blog posts What causes roof shingles to curl up at corners? and What causes shingles to buckle along a line on the roof?
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To learn more about roofs and attics, see these other blog posts:
• 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?
• 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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