Mechanical Damage to Asphalt Shingles - cuts, punctures, tears, granule loss
InspectAPedia® -
Photo guide to mechanically-damaged roof shingles & mineral granule loss
Shingle granule loss due to foot traffic or other shingle damage; roof damage during inspection in hot weather?
Shingle damage due to cuts, tears, misaligned roofing staples, or application errors
Types of roof shingle stains, causes, cures, prevention
Case study examines causes of damaged roof shingles and granule loss
This roof shingle damage diagnosis article describes the causes and effects of mechanical damage to shingles from a variety of sources: foot traffic, tears, punctures, tool cuts, or damage during shingle installation.
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The results of mechanical damage to asphalt shingles includes mineral granule loss from the shingles, leaks, or simply shorter roof life. Other common asphalt shingle failure factors discussed in this article series include
improper storage and handling of the asphalt shingles before installation, improper nailing, improper flashing (which
pertains to any roofing material), and defective asphalt shingle product material leading to thermal splitting,
cracking, blistering, staining, and in some cases curling or cupping shingles.
Here we present a series of photographs of asphalt roof damage. A professional investigator documented these conditions and joined in a discussion of the apparent cause of damage shown in each photo. All of these pictures were taken on the North slope of an asphalt shingle Firehalt brand roof.
A windstorm adjuster for TWIA (Texas) inspected an insured's roof with a large amount of granular loss.
The roof is in these photos is 10/12 pitch (hip with build ups) and was 11 years old at the time of inspection. The roof is vented by turtle vents (4) and (1) turbine vent only (no ridge vent). The shingles are Firehalt Brand (Certain Teed®) - 30 year shingles.
In our opinion the damage was not, however, related to the brand. Roof consultants, manufacturers, suppliers, and building inspectors are invited to Contact Us to offer further diagnostic comments about this case.
Damage due to improper installation - staple exposed, askew, not flush, wrong location & mis-nailed.
Looks like same type of damage as the prior shingle photo, due to improper installation - staple exposed, askew, not flush, wrong location & mis-nailed, but in this photo the staple itself is not visible.
Damage due to blown off hip shingle, improper nailing is most likely, possibly wind and failure to seal.
Damage due to improper installation - surface nailed broken shingle over excessive bend fracture - maybe installed in cold weather; granule loss on exposed top of hip/ridge intersection, weather or foot traffic.
Damage due to cracked hip shingle, weather-damage granule loss around fracture - moisture penetration of shingle contributes to granule loss due to the fracture
Damage due to same as the previous photograph: people often step right on this spot on roofs.
Photo not sharp, but this looks like a cracked shingle tab, defective product or mechanical damage (someone tried to lift the tab after it was sealed??
Damage due to diagonal tear in single, mechanical damage is most likely. See my article on thermal splitting but as this tear is not over a butt joint it is more likely due to tear during installation or tear if someone tried to lift the tab (less likely)
Damage due to vertical tear in shingle tab - IF this tear is over a butt joint (which it appears) this could be thermal splitting - if so the number and extent of these will increase on the roof; COULD be also torn due to application over a raised staple - you need to investigate this further
Damage due to shingle edge injury due to walking on the roof - note the wear on the very edge of most of the shingle tabs - looks like foot traffic wear
Damage due to torn shingle tab, appears depressed as if broken by foot traffic at low temp; if left side of tear originates at a butt joint, could be thermal splitting.
Damage due to what appears to be classic defective product, curling and thermal splitting, split runs through at least 3 shingle tabs in the photo.
Damage due to diagonal tar near wall flashing, foot traffic or damage during installation.
Also the wall flashing may be improper and leak prone - single long counter flashing caulked to brick is unreliable, and step flashing may be absent (investigate further - possible clue of improper workmanship, look for step flashing at every shingle along this juncture by carefully lifting the counter flashing, or by carefully lifting some shingle tabs) - a second cracking torn shingle may be present at lower left of photo.
Damage due to cracked or torn shingle, note evidence of mechanical damage including the very straight cut to the left of the diagonal tear. Some granule loss to left of the straight cut at photo lower left - foot traffic looks likely as well as possible tool damage)
Damage due lifting, torn shingle tab at photo center, not over a butt joint, looks like mechanical damage or tear during installation
Damage due horizontal weathered tear across center of two laminated single tabs, exposed substrate, appears to be defective product or mechanical damage in storage, transport, or installation that later appears as a cut or tear. This does not look like a splice shingle but the wear is similar. See SPLICE DEFECTS on ASPHALT SHINGLES.
Conclusions About These Contributors to Asphalt Shingle Damage & Mineral Granule Loss on This Roof
Primarily, questionable or perhaps even poor workmanship, use of staples, mis-located, staples askew, high raised-corner staples, mis-stapled on top of shingles, foot traffic, mechanical damage, possibly excessive bending in cold weather at the hip/ridge appear to be the problems on this roof. We also saw some minor mis-nailing or inadequate nailing leading to a single blow off at the roof hip.
Secondarily: a few of the cuts and damage could be defective product - see CRACKS in FIBERGLASS SHINGLES. At least one cut was made by a tool or implement.
Weather does not appear to be a root cause of this roof damage, though once a shingle has been worn by walking or mechanical damage the exposure of the shingle substrate accelerates wear and granule loss.
We would not characterize the prime problem of this roof as "granule loss" which was the original owner's concern. GRANULE LOSS from SHINGLES provides more details.
In our opinion the roof damage was not, however, related to the brand. Roof consultants, manufacturers, suppliers, and building inspectors are invited to Contact Us to offer further diagnostic comments about this case.
Walking on an Asphalt Shingle or Roll Roofing Roof can Cause Damage to the Roof
Walking on a roof can damage shingles in several conditions.
Asphalt Shingle Roof Damage from Walking on Fragile Roof Surface
Granule loss or actual shingle damage may occur on a roof being walked-on: walking on any asphalt shingle roof loosens some of the mineral granules from their attachment embedded in the asphalt used to impregnate and coat the shingle.
Walking on shingles that are brittle, cupped, curled, can damage them at any time, perhaps more so if the inspector steps on a raised, curled, or otherwise damaged portion of the shingle, or if the asphalt shingles are simply old, brittle, and fragile, even if flat.
We investigated a complaint against a home inspector charged with damaging a roof that we learned he had been smart enough to stay off of - inspecting from the roof edge by ladder. But a contractor, called to bid on roofing repairs, stomped around inspecting the roof to make his repair bid. The result was conversion from a roof that needed replacement soon to one that needed immediate replacement. We could virtually see the footprints of the contractor, in a trail of broken shingles across the roof.
Asphalt Shingle Roof Damage during Other Repair Work
On roof repair work of other components, for example around a chimney, involving standing, moving, turning, placing repair materials on the roof surface without first protecting that surface from damage.
If there is a lot of roof traffic, such as when work is being done on a chimney, you may see "bald" areas of shingles with lost granules where people have been walking. This is damage caused by workers and is not a product defect.
Roof Damage from Walking on very Hot, soft Asphalt Roofing
We think it's subjective, and we don't have a specific number, but the variables underlying roof damage during an on-roof walking inspection include:
outdoor air temperature at the time of the roof inspection
sun exposure on different roof slopes - a shaded slope may be cooler and safe to walk-on even on a hot day
number of hours the roof has been exposed at various temperatures - longer roof exposure to sun and high temperature on a given day, walking on a roof in the last half of a very hot day, for example, is more likely to lead to damage
the nature of the foot traffic - walking carefully vs. standing in one place and spinning on your heels - the latter will certainly damage a hot soft asphalt shingle or roll roofing.
Alone no single number answers the questions raised by these factors.
But certainly we've both seen damage to roofs when walked on during a hot day - when someone was careless.
Thanks to home inspector Charlie Gallagher for suggesting this added detail.
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Randy LeBlanc, a Windstorm Adjuster for TWIA (Texas), provided photographs and assisted in technical assessment of this material 4/12/09.
Charlie Gallagher is a professional home inspector in Lawton, OK and can be contacted at CAGFISHING@aol.com
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
Architectural elements: the technological revolution: Galvanized iron roof plates and corrugated sheets; cast iron facades, columns, door and window caps, ... (American historical catalog collection), Diana S Waite, available used out of Amazon.
Green Roof Plants: A Resource and Planting Guide, Edmund C. Snodgrass, Lucie L. Snodgrass, Timber Press, Incorporated, 2006, ISBN-10: 0881927872, ISBN-13: 978-0881927870. The text covers moisture needs, heat tolerance, hardiness, bloom color, foliage characteristics, and height of 350 species and cultivars.
Green Roof Construction and Maintenance, Kelley Luckett, McGraw-Hill Professional, 2009, ISBN-10: 007160880X, ISBN-13: 978-0071608800, quoting: Key questions to ask at each stage of the green building process Tested tips and techniques for successful structural design
Construction methods for new and existing buildings
Information on insulation, drainage, detailing, irrigation, and plant selection
Details on optimal soil formulation
Illustrations featuring various stages of construction
Best practices for green roof maintenance
A survey of environmental benefits, including evapo-transpiration, storm-water management, habitat restoration, and improvement of air quality
Tips on the LEED design and certification process
Considerations for assessing return on investment
Color photographs of successfully installed green roofs
Useful checklists, tables, and charts
Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used)
Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502
Slate Roofs, National Slate Association, 1926, reprinted 1977
by Vermont Structural Slate Co., Inc., Fair Haven, VT 05743, 802-265-4933/34. (We recommend this book if you can find it. It
has gone in and out of print on occasion.)
Roof Tiling & Slating, a Practical Guide, Kevin Taylor, Crowood Press (2008), ISBN 978-1847970237, If you have never fixed a roof tile or slate before but have wondered how to go about repairing or replacing them, then this is the book for you. Many of the technical books about roof tiling and slating are rather vague and conveniently ignore some of the trickier problems and how they can be resolved. In Roof Tiling and Slating, the author rejects this cautious approach. Kevin Taylor uses both his extensive knowledge of the trade and his ability to explain the subject in easily understandable terms, to demonstrate how to carry out the work safely to a high standard, using tried and tested methods.
This clay roof tile guide considers the various types of tiles, slates, and roofing materials on the market as well as their uses, how to estimate the required quantities, and where to buy them. It also discusses how to check and assess a roof and how to identify and rectify problems; describes how to efficiently "set out" roofs from small, simple jobs to larger and more complicated projects, thus making the work quicker, simpler, and neater; examines the correct and the incorrect ways of installing background materials such as underlay, battens, and valley liners; explains how to install interlocking tiles, plain tiles, and artificial and natural slates; covers both modern and traditional methods and skills, including cutting materials by hand without the assistance of power tools; and provides invaluable guidance on repairs and maintenance issues, and highlights common mistakes and how they can be avoided.
The author, Kevin Taylor, works for the National Federation of Roofing Contractors as a technical manager presenting technical advice and providing education and training for young roofers.
The Slate Roof Bible, Joseph Jenkins, www.jenkinsslate.com,
143 Forest Lane, PO Box 607, Grove City, PA 16127 - 866-641-7141 (We recommend this book).
Solar heating, radiative cooling and thermal movement: Their effects on built-up roofing (United States. National Bureau of Standards. Technical note), William C Cullen, Superintendent of Documents, U.S. Govt. Print. Off (1963), ASIN: B0007FTV2Q
"Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
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