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Book Review: Aluminum Sheet Metal Work in Building Construction
12-26-02
Publisher: The Aluminum Association
Aluminum is often a material of choice in roofing and flashing applications. Why? Certainly aluminum is economical, readily available, easy to fabricate, highly resistant to corrosion, and can be left to weather in its natural state or painted or anodized for decorative purposes. Which aluminum alloys are applied for these applications, and what are best practices for their design and installation? These questions are addressed in the recently reissued Aluminum Association publication entitled Aluminum Sheet Metal Work in Building Construction. This publication, which is also part of the more extensive Aluminum Design Manual 2000, has been prepared for use by architects, contractors, building officials, and students.
The publication starts with an overview section describing the primary characteristics of aluminum sheet for building construction. These topics include corrosion resistance, workability, joining and sealing, and finishing. It's noted that while aluminum has good inherent corrosion resistance as a result of the naturally-occurring oxide film, dissimilar metal or galvanic corrosion must be kept in mind when and addressed in design and installation. Workability as well as the light weight of aluminum sheet provide benefits both in the shop as well as at the job site. Joining and sealing using mechanical seams and other joints are the same for aluminum as for other sheet metals. Finally, finishing, including embossing, painting, and anodizing, are used effectively for both decorative and corrosion resistance functions.
Following this introductory section is a description of the aluminum sheet alloys and tempers that are primarily utilized in sheet metal work. A brief discussion of the alloy and temper designation system is provided to orient the reader. 3004-H14 is the sheet product generally used in this area, with a number of acceptable alternative alloys in the 1xxx, 3xxx, and 5xxx non-heat treatable alloy systems listed as well. Typical mechanical properties of these alloy/temper combinations are provided in tabular format for comparison.
The bulk of the publication focuses on the specifications themselves. The scope statement states "these specifications shall apply to the proper use of aluminum in roofing, flashing, and other sheet metal work in building construction. They are not intended to cover the details or specifications or proprietary or pre-formed sheet metal systems or products such as horizontal siding fascia and soffit systems, curtain wall systems, corrugated or ribbed roofing and siding, etc." The specification reviews the materials aspects, including not only the aluminum alloys but also the building paper or roofing felt, sealants, elastic cement, fasteners, and paint. Regarding surface preparation, the specification discusses issues related to dissimilar metals, wood sheathing, and concrete and masonry. The section on dissimilar metals is especially helpful as it discusses under what circumstances and with which metals galvanic corrosion could be anticipated. A section on joining covers the various methods such as mechanical seams and joints, brazing, and welding. It is noted that soldering of aluminum is not permitted by this specification. A table of filler alloys for fusion welding the various base sheet metal alloys is given as an aid to selection.
The remainder of the publication focuses on specifications for various sheet metal constructions, and covers standing seam roofing, batten seam roofing, aluminum roof shingles, flashing, valleys, gravel stops, coping covers, and rainwater goods. A final section deals with aluminum composite materials used in sheet metal construction. All of these sections are presented with illustrative drawings of the relevant construction details.
Aluminum Sheet Metal Work in Building Construction as well as Aluminum Design Manual 2000 is available from the Aluminum Association online at www.aluminum.org.
Article provided courtesy of The Aluminum Association - www.aluminum.org
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