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This article explains how to identify & evaluate shingles installed in a "ladder pattern" and describes roof leak, wear, and cosmetic issues caused by shingle laddering as
an example of something a bit less than the "best" roof installation workmanship.
These defects occur on organic-mat or fiberglass-mat
asphalt roof shingles. Readers are also invited contribute roof failure information to the web author for research purposes.
web author for research purposes. Readers should also see ASPHALT SHINGLE INSTALLATION.
The first photograph here shows a sloppy "ladder pattern" installation of strip-type asphalt shingles. While opinions (and expertise) vary
among roofers, this ladder pattern shingle application may not be as durable a roof installation as one which staggered the shingle offsets more than a
single
six inches (or in this case only 3") left and right with each shingle course.
Photo of fishmouthed/laddered shingles at above-right right is courtesy of ASHI home inspector Carl Gerosa, New Rochelle, NY.
On other asphalt shingle roofs, particularly older ones,
you may notice that the pattern of fishmouth occurrence on an asphalt shingle roof follows a fairly regular or stair-stepped
pattern, or it may follow a regular "ladder" like pattern up the roof such as is shown in these photographs.
That's because the fishmouthing is occurring at
the butt joints of the shingles where more moisture is passing out of the roof structure into the back side of the shingle
above each butt joint.
You can thus determine the actual pattern in which the shingles were applied to the roof. "Laddering," while
permitted by some manufacturers and standards, is a less workmanlike shingle installation and may result in a localized early
wear area on a roof. Ladder-pattern shingle application shows that the roofer liked to work up the roof from one position for
as long as possible before moving.
Since this lines up
butt joints every other course, this is considered a less watertight
roof and may leak under extreme situations, such
as windblown rain on a low pitch.
It is not recommended
by any roofing manufacturers. Manufacturers also claim
that shingle color patterns may create splotches or stripes
if laid this way.
A Forensic Engineer's Comments on Shingle Laddering and Asphalt Roof Shingle Wind Damage
Nail Omissions - leaving out some nails - is at fault in laddered shingle blow-offs
On the photo of the laddering problem submitted by Carl Gerosa of New Rochelle, NY: I have found that the loose corners are most often associated with the installer neglecting to place the nails at the ends of the shingles when installing the subsequent rows.
It is not necessarily the result of installing the shingles in a straight line up the roof. The same problem will occur diagonally when the nails are neglected (the common term is "three-nailing"). If the nails are all in the right place, the corners generally stay down either way.
Also see Mr. Skees' comments about nailing errors & asphalt shingle cellophane strip removal at WIND DAMAGE to ROOFS
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Carl Gerosa, Target Inspection Consultants, Inc., New Rochelle, NY 10804, Tel: 914-833-2900 / 914-834-7494, New York Home Inspectors License Number: NY 1600005625/CT 20 is a certified ASHI inspector and a member of CAHI, the Connecticut Association of Home Inspectors. Mr. Gerosa provides home inspections of Single Family Homes, Radon Testing, Wood Destroying Organisms. Email: targetinspection@aol.com
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com
Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com
Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY
Thanks to James A. Skees, PE, President and Sr. Forensic Engineer, OnTheRock Engineering, LLC, 604 W. Jefferson Street, LaGrange, KY 40031
502-225-6203 FAX 225-6204, for commenting on the roof cellophane strip problem, on wind damage to roof shingles, shingle blow off, improper shingle nailing, and roof shingle laddering underlying defects, August 2010. Mr. Skees is a forensic engineer who works for insurance companies. Mr. Skees can also be reached by email at jimskees@ontherockeng.com
The company has published online a sample Tornado Report
"Residential Wind Damage Evaluation", Wind Damage Sample, found at http://www.ontherockeng.com/Sample%20Tornado%20Report.pdf
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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