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This article discusses the properties of wood roof shingles and shakes, including shingle grades, wood species used in roofing, and wood roof shingle or shake warranties. This article series discusses best practices in the selection and installation of residential roofing. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.
Our page top photo shows a wood shingle roof on the historic Mesier Homestead in Wappingers Falls, NY.
Wood shakes and shingles are traditional American roof
coverings dating back to Colonial times. They remain popular
in many coastal areas and are common or even mandated
in certain historic districts. Traditionally, wood roofs
were laid on spaced sheathing, which provided good ventilation
around the shingles and contributed to a service
life of 30 years or more.
New wood roofs set on solid
sheathing have been known to fail in 10 years or less unless
the installer takes adequate precautions to allow for
good drainage and drying of the wood roofing materials.
With installed costs of over $600 per square for premium
materials, it is important to design a roof that will last.
Materials Used in Wood Shingle & Shake Roofs
Wood shakes and shingles soak up water through their end
grain, dry unevenly in the sun, and slowly erode on the surface
from a combination of ultraviolet radiation, wind, and
precipitation. In humid conditions, wood shingles may become
a breeding ground for moss, lichen, and decay fungi.
To survive those harsh conditions, wood roofing should be
made from a durable wood species that is either naturally
decay-resistant or pressure-treated.
Wood Species for Wood Shingle or Shake Roofs
The most commonly used wood on
roofs today is western red cedar. The heartwood of red
cedar is rich in extractives that provide natural decay
resistance. Eastern white cedar also has good decay resistance
and is commonly used on the East Coast. However,
white cedar is typically flat-sawn and has a mix of
heartwood and sapwood, making it less durable on a roof
and more prone to cupping and splitting. Other less common
species with good track records are Northern white
cedar, Alaskan yellow cedar (actually a cypress), and
Whatever species is selected, use the best grade available.
With red cedar and other decay-resistant species, the
heartwood is far more decay-resistant than the sapwood.
Edge-grain wood is more stable and less prone to cupping
and splitting than less expensive flat-grain wood. The best
choice for wood roofing is all-heart, edge-grained shakes
Wood Shingle & Shake Shingle Grade Choices
Make sure the lumber to be purchased has been
graded under the authority of a recognized grading agency
such as the Cedar Shake and Shingle Bureau for red cedar
or the Southern Pine Inspection Bureau for yellow pine. A
blue label on the packaging, for example, may simply be a
marketing tactic and does not necessary indicate that the
shakes or shingles are certified as Grade 1.
Wood Shingle & Shake Roof Warranties
If installed in accordance with the Cedar
Shake and Shingle Bureau’s specifications by a certified
installer, the CSSB will guarantee wood roofing for 20
to 25 years, depending on the thickness of the shake or
shingle. Some pressure-treated shakes and shingles carry
warranties of up to 50 years.
Preservative Treatment for Wood Shingle or Shake Roofs
If premium red or white
cedar is too expensive, consider pressure-treated southern
yellow pine shakes and shingles. In its favor, yellow pine
is a tougher and stronger wood, and although not as pretty
as red cedar when new, over time they will both weather to
a similar silver gray. Because penetration of the treatment
is nearly 100%, pressure-treated pine shingles carry guarantees
against decay for up to 50 years, making them well suited
to high-moisture environments, shallow slopes, and
shady wooded sites where organic matter may collect on
the roof. The preservatives should not leach out over time.
One drawback to yellow pine shingles and shakes is
that many are flat-grained, so most come pretreated with a
water repellent to help them resist cupping and splitting.
However, retreatment with a water repellent at some point
may be required for optimal performance. Western red
cedar shingles are also available pressure-treated for
severe applications where standard cedar shingles are
prone to decay.
Shingles are sawn from blocks of wood, which
gives them two smooth faces. They are relatively thin and
cut to a taper. Red cedar shingles come in four grades, but
most roofs use No. 1 or No. 2, which are all edge-grain
heartwood (Table 1-6 below). They are available rebutted
and rejointed (R&R), where a uniform appearance is desired,
or machine-grooved for a textured surface.
[Click any image or table for a larger, more detailed version.]
Eastern white cedar shingles are also available in four
grades. Most roofing work uses Grade A (Extra), which is
all-clear, all-heartwood, or Grade B (Clear), which has no
knots on the exposed face (see Table 1-7 shown below).
Characteristics & Grades of Wood Roof Shakes
Shakes are split from large blocks of wood and
may be resawn to create a taper. They are heavier than
shingles, less uniform in thickness, and are generally
rough-textured on one or both sides creating a more rustic
appearance. Grades and characteristics for red cedar
shakes and shingles are found in Table 1-6 shown earlier. Red
cedar shakes come either tapered or untapered and are usually
installed on roofs in Premium or No. 1 grade.
Fire-Retardant Treatment for Wood Shingle Roofs
Once popular on the West
Coast, wood roofs have been banned in many residential
areas by fire regulations designed to slow the spread of
Fire-retardant treated (FRT) shingles and shakes
have been developed to address these issues and can obtain
a Class B or C rating when combined with other components
in a fire-resistant roof system. With pretreated shingles,
consult with the treating company regarding fastener
requirements and any special application instructions.
Air Vent/A Gibraltar Company
A complete line of roof ventilation products, including
shingle-over and exposed-ridge vents with exterior wind
baffles and internal weather filters. Also soffit and drip
edge vents and passive and powered attic turbine-type
Shingle-over ridge vents. Low-profile Roll Vent uses nylonmatrix.
Extractor vent is molded polypropylene with internal
and external baffles.
Shingle-over low-profile ridge vents, including Cor-a-vent,
Fold-a-vent, and X-5 ridge vent, designed for extreme
weather. Corrugated core.
GAF Materials Corp.
Cobra vent: roll-out shingle-over ridge vent with a
102 CHAPTER 2 | Roofing
Mid-America Building Products
Ridge Master and Hip Master shingle-over molded plastic
ridge vents with internal baffles and foam filter
VentSure corrugated polypropylene ridge vents; also
passive roof vents and soffit vents
Trimline Building Products
Shingle-over low-profile ridge vents, Flow-Thru battens for
Elk Premium Building Products
Highpoint polypropylene shingle-over ridge vents
Tamko Roofing Products
Shingle-over ridge matrix–type Roll Vent and Rapid Ridge
(nail gun version) and Coolridge, which is molded
polypropylene with external and internal baffles
Cedar Breather, a
3/8 -in.-thick matrix-type underlayment
designed to provide ventilation and drainage space under
More Information about Roofing Materials, Methods, Standards
Asphalt Roofing Manufacturers Association (ARMA)
Cedar Shake and Shingle Bureau
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, 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. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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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
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).