Asphalt Roll Roofing Installation, Defects, Repairs
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This article describes mineral-granule coated asphalt roll roofing roofing materials, choices, installations, inspection, defects, roofing repairs, and product sources.
Our page top photo shows our client pointing to a low slope area on a roof where mineral-granule coated asphalt roll roofing was applied after shingles in that location had leaked repeatedly.
Because mineral-granule-coated modified bitumen roofing can be mistaken for roll roofing, and vice versa, readers should also see MODIFIED BITUMEN ROOFING.
Roll roofing is simplest product to install on a small section of lowslope
roof is 90-pound roll roofing. This consists of a heavy,
asphalt-saturated organic or fiberglass felt with a granular
surface. Rolls are 36 inches wide and weigh 90 pounds.
Single-coverage roll roofing typically has a 2-inch lap with
exposed nails and is used mainly on utility structures.
Double-coverage roll roofing is installed with a full
19-inch lap joint, leaving a 17-inch exposure, with a 2-inch
head-lap. Nails are concealed under the lap joints that are
sealed with asphalt lap cement. With two layers of protection,
double-coverage roll roofing is acceptable for small
roof areas and can be used on roofs as shallow as 1:12.
In its earliest forms roll roofing consisted of sheets of felt canvas or cloth that were
impregnated with asphalt, then rolled flat along a low-slope or even some steeper sloped roofs with the material's long edge parallel to the building eaves.
Modern 90-pound asphalt roll roofing is built of mineral-coated fiberglass-reinforced mat or organic-mat (bituminous impregnated paper) material very similar to asphalt roof shingles, in 36-inch wide material sold in 36-foot long rolls. Roll roofing is coated on both sides with asphalt and its upper or exposed side is protected with mineral granules. Common colors are white, brown, black. You may find some roofers referring to roll roofing as "90-pound felt" since a 36-foot roll of the material, able to cover about 100 sq.ft. (one roofing "square") weighs close to ninety pounds.
Our roll roofing material photo (left) shows that this roll was a bit out of round. When buying roll roofing avoid rolls that are squashed as they may be difficult to roll out smoothly (give the material time to relax and flatten before nailing). Also avoid rolls whose ends are badly damaged as it may make for uneven or raised seams.
This is an inexpensive roofing material often installed (over 15# felt underlayment) by homeowners and do-it-yourself-ers.
Nonetheless roll roofing installations will have a longer life if installed according to the product manufacturer's instructions, nailed at proper intervals, and with seams properly sealed. It's also important to install roll roofing over a smooth sound roof deck. If the roof decking sags, ponding on the roof surface after rain may reduce its life.
Overlapping strips of asphalt roll roofing are installed over the roof surfaces with overlapped edge joints sealed, usually with a heated asphalt compound, or cold-applied using a similar sealant that functions at lower temperatures.
Probably in part because asphalt roll roofing is typically used on low slope and nearly flat roofs, it can have an anticipated wear life of less than ten years, often five years. The roof life may be extended by coatings.
Common Problems on Roll-Roofing Covered Roofs
As Carson Dunlop's sketch (below) illustrates, a common roll roofing problem includes wrinkles or bubbles. Granule loss and exposure of "bald spots" or cracking are common signs that roll roofing is at the end of its life.
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Additional technical contributors & reference sources for this article are listed below.
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"Choosing Roofing," Jefferson Kolle, January 1995, No. 92, Fine Homebuilding, Taunton Press, 63 S. Main St., PO Box 5506, Newton CT 06470 - 800-888-8286 - see http://www.taunton.com/FineHomebuilding/ for the magazine's website and for subscription information.
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.
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.)
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).
"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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