Book Review: Slate Roofs

Slate Roofs has long been the essential go-to guide for determining material quantities, roof layout, specification data and construction details.
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Slate Roofs has long been the essential go-to guide for determining material quantities, roof layout, specification data and construction details.

Slate Roofs: Design and Installation Manual
National Slate Association; Poultney, VT; 2010
271 pp; hardcover; $125
ISBN 978-0-615-39465-7

Reviewed by Suzanna Barucco

More than 100 detailed drawings are provided.

More than 100 detailed drawings are provided.

Anyone who has detailed a slate roof, or any other type of traditional steep slope roof, is likely to be familiar with Slate Roofs, published by the National Slate Association in 1926. Published more than 85 years ago, Slate Roofs has long been the essential go-to guide for determining material quantities, roof layout, specification data and construction details.

The National Slate Association (NSA), dormant since the Great Depression, reorganized in 2002 and took on the task of producing an update of the 1926 manual, Slate Roofs: Design and Installation Manual – 2010 Edition. Designers and installers alike will want to have a copy close at hand to refer to the plethora of design details that are both illustrated and explained at length. The manual achieves a core mission of the National Slate Association: to disseminate information about, and provide education materials for, the slate roofing industry. More than just a design and installation manual, the 2010 edition of Slate Roofs is an extensive exploration of current standards and practices for roofing with this long-lasting, natural material.

As stated in the introduction, the performance and aesthetic success of a slate shingle roof installation is dependent upon the coordinated contributions of designers, suppliers and installers, and the committee responsible for this new edition reflects this diverse group. The committee, co-chaired by Jeffrey S. Levine, a roof and building envelope consultant based in Ardmore, PA, and Danny L. Cornwell, a roofing contractor in Portland, OR, was comprised of roofing contractors Alan Buohl, GSM Roofing (Ephrata, PA), Matt Millen, Millen Roofing Company (Milwaukee, WI.), and Clark Chase, IV, Constructions Collaborative, Inc. (Waltham, MA), roof consultant Russel Watsky, Russel Watsky, Inc. (Ossining, NY), and supplier David Large, North Country Slate (Toronto, Ontario, Canada).

Levine, who served as editor, has been researching and writing about slate roofing and the roofing slate industry for 25 years. Among other publications, he is perhaps best known as the author of Preservation Brief 29, The Repair, Replacement & Maintenance of Historic Slate Roofs (NPS, 1992). His firm, Levine & Company, Inc., has won numerous awards for construction documentation and innovation in roofing design.

The manual is organized from an installer's, rather than a designer's, point of view, similar to the earlier edition, with the opening chapters addressing specialty tools of the trade, materials and equipment checklists, and site safety considerations. With more than twice as many pages as the 1926 edition, the 2010 manual offers designers and installers alike, many more design details along with extensive explanatory notes. In addition to an index, a detailed Table of Contents includes a list of sidebars, tables and figures found throughout, allowing any user to quickly locate a topic or particular detail.

Chapter One, "The Nature and Characteristics of Slate," provides basic information on slate as a material, including available colors and natural features such as knots, knurls and cramps. The 2010 manual has been updated to include mention of the wider range of slate sources now available, including China and Brazil, although readers wanting information on the quality of these materials will have to look elsewhere. A section on commercial slate standards, including grading, helps to demystify industry terminology, describing weight, thickness and material longevity, and the basis of ASTM standards for slate, all essential aspects of material selection.

This is followed by a chapter on the "Basic Principles" of preparing for a slate roofing project, from a discussion of specialized slater's tools and equipment to estimating quantities and laying out slates on the roof, and including safety considerations and code issues. A welcome improvement over the line sketches in the original manual is the addition of color photographs to highlight the various ways that slate can be used as a design element in its own right. Patterns in color and shape, size and thickness gradations, and various laying methods, such as the less common hang-down style, are shown.

The essential value of Slate Roofs is found in the "Installation Details" chapter. Here the manual departs considerably from the 1926 edition, and is more akin to construction manuals such as Copper and Common Sense (Revere Copper Products, Inc., 2005) and the Architectural Sheet Metal Manual (Sheet Metal Manufacturers Association, 2012).

While readers are cautioned to use the manual as a guide, accommodating the climate and specific design needs of each project, more than 100 detail drawings are provided. Included are common details, such as various methods for constructing eave, valley, ridge and hip flashings, to the less common slate roof expansion joint and eyebrow dormer flashing. In addition to the Table of Contents, this chapter opens with a drawing of a generic building with roof elements and relevant details identified, a handy way of easing the manual user's ability to hone in on a specific roof condition. Each flashing detail, for which there may be up to five options, is preceded by an explanation of the detail, the materials used, and related aspects of roof construction, such as underlayments and potential code requirements.

The final chapters are devoted to "Roof Repair" and "Specialty Systems," where snow retention systems and fire, wind, seismic and vapor considerations for slate roof design are addressed. Nine appendices include a glossary, roof slope conversion table, ASTM Standards related to slate roofing, and relevant roof framing information, focusing on rafters, hips and valleys.

Slate Roofs: Design and Installation Manual was recognized with a Gold Circle Award from the National Roofing Contractors Association in 2011. The group continues to develop content for its website (www.slateassociation.org) as a resource for the industry. Slate Roofs is available in hardcover, softcover and as a CD from the National Slate Association's website.

Suzanna Barucco is President of sbk + partners, LLC, a historic preservation consulting firm in Ardmore, PA. She has designed slate and other roofing installations for residential and institutional buildings, often as a part of comprehensive exterior restoration projects. Barucco received an MA in Historic Preservation Planning from Cornell University and is a lecturer in the Historic Preservation Program at the University of Pennsylvania, and an adjunct professor and consultant for the Historic Preservation curriculum at Philadelphia University.