Comparing Metals Used in Metal Roof Systems
InspectAPedia^® -

Types & properties of metals used in metal roofing system
Galvanized Steel Metal Roofing System Properties
Aluminized Steel Metal Roofing System Properties
Galvalume Metal Roofing System Properties
Aluminum Metal Roofing System Properties
Copper Roof Metal Roofing System Properties
Zinc Metal Roofing System Properties

This article discusses the different types of metal used in metal roof systems, the properties of each metal, and their application, including galvanized steel roofs, aluminized steel roofs, galvalume roofing, aluminum roofs, copper roofs, and zinc metal roof systems.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.

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.

Also see A Complete List of Types & Properties of Metal Used in Roof Systems, and see our metal roofing home page, METAL ROOFING and see CORRUGATED ROOFING and COPPER ROOFING.

© Copyright 2012 InspectAPedia.com, Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

A Comparison of Metal Choices for Roofing Systems

Adapted/paraphrased with permission from Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES: [Click any table or image to see an enlarged version.]

While some companies offer roofing products in copper, zinc, and stainless steel, the vast majority are coated steel and aluminum. Coated steel products are the most common and least expensive. In its favor, steel moves relatively little with temperature changes, has good structural characteristics, and resists denting. Its high melting point gives it a Class A fire rating.

All coated steel materials, however, are vulnerable to corrosion at field-cut edges— although Galvalume® is the least affected Table 2-10 below lists the advantages, drawbacks, compatibility, and life expectancy of galvanized steel roofing, aluminized steel roofing, galvalume, aluminum, copper, and zinc metal roofing products. Also see our separate article, A Complete List of Types & Properties of Metal Used in Roof Systems.

Table 2-10: Metal Roofing Characteristics (C) J Wiley, S Bliss

Aluminized Steel Metal Roofing System Properties

Developed in the 1950s, this is similar to galvanized steel, but it uses aluminum as the coating instead of zinc. The aluminum provides a physical barrier against corrosion and creates a reflective surface that helps reduce heat transfer to attics. However, aluminum does not have the self-healing properties of zinc, so exposed edges and scratches are more susceptible to rust.

Aluminized steel generally outlasts galvanized steel but has largely been replaced in the market by Galvalume® Metal Roofing

Aluminum Metal Roofing System Properties

Details about aluminum roofing materials are at ALUMINUM ROOFING, excerpts are below.

Aluminum that is anodized or painted is highly resistant to corrosion, making it well-suited to coastal environments provided it is factory-coated with a suitable finish. (although lightweight aluminum flashings tend to pit and oxidize in salty air).

Aluminum roofing's light weight is an advantage in reroofing. Aluminum roofing also reflects heat and may thus reduce building cooling costs in hot sunny climates.

Because of its high coefficient of expansion, however, attachment systems must be designed to accommodate the movement of long aluminum roof panels.

Also see ROOF NOISE TRANSMISSION where we describe the noise transmission properties of metal roofing.

Also see A Complete List of Types & Properties of Metal Used in Roof Systems

Copper Roof Metal Roofing System Properties

This high-end material is highly resistant to corrosion and easily formed into panels. Copper roofs have been known to last for over a century and are a common sight on churches and historic buildings.

Left unfinished, the material will oxidize to the familiar green patina (photo) that protects the underlying metal. In arid areas, the color may be more reddish-purple. Special clear acrylic coatings can be applied that will help copper retain its original color.

One concern is that runoff from a copper roof can stain building components below if not managed with gutters. Also, premature failure of copper flashing and roofing has been linked to acid rain and runoff from cedar shingles (see FLASHING WOOD ROOF DETAILS under WOOD ROOF SHINGLE PROPERTIES)

Clients interested in copper should consider a newly developed proprietary sheet metal called Suscop™, which has copper plating over a stainless-steel core. The material combines the strength and durability of steel with the natural patina of real copper. Because of its greater strength, a lighter-weight sheet (0.4mm) can be used in place of 16-ounce copper, significantly reducing material costs.

Details about copper roofing are found at COPPER ROOFING.

Galvanized Steel Metal Roofing System Properties

To protect against corrosion, the steel is bonded to a layer of zinc, which works as a sacrificial coating on the surface and also offers some protection to cut edges and nicks by flowing to these areas. The heavier the zinc coating, the longer the protection. The Metal Roofing Alliance recommends G-90 galvanized steel for roofing, which has 90 ounces of zinc per square foot.

Details about galvanized metal roofing are at Galvanized Steel Roofing.

Also see A Complete List of Types & Properties of Metal Used in Roof Systems for more about galvanized steel roofing.

Galvalume® Metal Roofing System Properties

Also sold under the trade names Zincalume ® and Galval®, Galvalume® was developed in the early 1970s. The underlying steel is coated with a zinc aluminum alloy that combines the long-lasting protection of aluminum with the self-healing properties of zinc.

Details about Galvalume® are at Galvalume Metal Roofing

Also see A Complete List of Types & Properties of Metal Used in Roof Systems for more about Galvalume.

Stainless Steel Roofing System Properties

Stainless steel is generally a rust-resistant material but it's corrosion resistance to salt depends on the stainless steel alloy or grade. Also, stainless steel roofing durability depends on installation and ventilation details. Stainless steel grade 316) work well is suitable for salt-spray areas.

Terne coated stainless steel roof panels (Terne coating is a a zinc-tin alloy metal coating process that gives extra corrosion resistance. Other terne coatings using lead can present an environmental contamination worry from lead leachate found in roof runoff.)[1]

Because it is harder than aluminum metal roofing, stainless steel roof panels will be more resistant to impact damage from hail, and the metal also has less thermal expansion/contraction movement than either aluminum or copper roofs.

Watch out: other grades of stainless steel (SS 304) are not recommended for use near areas of salt spray such as close to oceans. And to avoid pitting-corrosion, stainless steel roof panels are installed using methods to provide panel ventilation on both the exposed and down-facing sides.

Details about terne metal roofing are at TERNE METAL ROOFING

Sources of Stainless Steel Roofing Products

Corrugated Metal Roofing and Paneling, Stainless Steel, 82 Walker Lane, Newton PA 18940, Tel: 215-860-3600, http://www.corrugatedmetal.com/ including Stainless steel 303 machinable and corrosion resistant steel.
Euro Inox, European Stainless Steel Development Association, http://www.euro-inox.org/ publishes a Technical Guide to Stainless Steel Roofing at http://www.euro-inox.org/htm/p_5_EN.html - Quoting

Reasons for Stainless Steel in Roofing In architectural applications, stainless steel is often used because of its attractive appearance. Facades, interior cladding, lifts and escalators, handrails and parapets are some of the most typical areas of stainless steel use. The family of stainless steels, however, has more to offer than just good looks. Its technical properties make it an ideal choice for many other building applications, in which additional durability requirements are essential.

Stainless steel is an alloy containing at least 10.5 % chromium 1). This gives the steel an inherent ability to protect itself from corrosion. Chromium in the steel reacts with oxygen in the air and/or water to which the steel surface is exposed, and forms an invisible protective film of a chromium-rich oxide. If this layer is damaged, mechanically or chemically, it is spontaneously rebuilt if oxygen is present. Corrosion resistance is increased with higher chromium levels and, additionally, by adding molybdenum to the alloy. The presence of nickel improves formability and weldability. Nickel-containing stainless steels work-harden on cold forming and can thus give the fabricated part an additional structural function. The most commonly used stainless steels have a chromium content of around 17 - 18% and a nickel content of 8 – 10.5%. This is why they are known as "18/8" or "18/10". These chromium-nickel grades are called “austenitic stainless steels” Another family of stainless steels are mainly alloyed with chromium and possibly other elements like Titanium. These are called “ferritic” grades. For roofing purposes, 12 - 17% chromium grades with organic or metallic coatings can be used.

Flexospan Stainless Steel roofing and siding,PO Box 515, 253 Railroad St., Sandy Lake PA 16145, 800-245-0396, http://www.flexospan.com/ products: Flexbeam, Flexrib, Ventarib stainless steeel roofing panels.
Follansbee Stainless Steel Roofing, see http://www.follansbeeroofing.com/ and Follansbee's description of their ZT Alloy steel roofing
James River Steel, PO Box 11498, Richmond VA 23230, 800-825-0717, Email: info@jamesriversteel.com - Corrugated Stainless Steel Roof Panels, http://www.jamesriversteel.com/ - corrugated panels in stainless steel, flooring, aluminum, galvanized steel and fiberglass for industrial and architectural roofing, siding and decking.
Stainless Steel Information Center, Specialty Steel Industry of North America, SSINA, 3050 K Street, N.W., Washington, DC 20007 Tel: (202) 342-8630 (800) 982-0355 http://www.ssina.com/

Zinc Metal Roofing System Properties

Zinc roofs are similar to copper in their durability and also similar to copper roofs in their installation procedures. But unlike copper, zinc roofs weather to a bluish-white color rather than green. Zinc roofing material, widely used in Europe, is very malleable and can be formed into intricate patterns for metal shingles.

Details about zinc metal roofing are at Zinc Metal Roofing

Also see A Complete List of Types & Properties of Metal Used in Roof Systems

-- Adapted with permission from Best Practices Guide to Residential Construction.

Resources: Roofing Materials & Equipment Suppliers

Where to Buy Metal Roofing: Manufacturers & Metal Roofing Sources, Associations

Metal Roofing

Atas International www.atas.com Modular metal shingle, tile, and standing-seam panels
Classic Products www.classicroof.com Modular metal shingle panels and standing seam panels
Custom-Bilt Metals www.custombiltmetals.com Modular metal shakes and standing seam panels
Decra Roofing Systems www.decra.com Modular metal shingle, tile, and shake panels
Dura-Lok Roofing Systems www.duraloc.com Modular metal roofing shingles with granular coating
Fabral www.fabral.com Exposed fastener and concealed clip metal roofing panels
[1] Follansbee Steel Roofing, Follansbee WV 26037, Tel: 304-527-1260 800-624-6906, ZT Alloy (corrosion resistant terne-coated stainless steel roofing) - http://www.follansbeeroofing.com/
Gerard Roofing Technologies www.gerardusa.com Modular metal shake and tile panels with granular coating
Met-Tile www.met-tile.com Modular metal roof-tile panels
Millenium Roof Tiles,550 East Centralia Street Elkhorn, WI 53121,Tel: 262-723-7778, produces stainless steel roofing tiles, 50-year warranty, http://www.millenniumtiles.com
Zappone Manufacturing, website www.zappone.com/
Zappone Manufacturing, 2928 North Pittsburg St. Spokane, WA 99207 1-800-285-2677, Washington State Copper Roofing Supplier of Copper scallop shingles, copper shingles, copper bay windows, vertical walls, aluminum roof shingles

Venting Underlayments

Benjamin Obdyke www.benjaminobdyke.com Cedar Breather, a 3/8 -in.-thick matrix-type underlayment designed to provide ventilation and drainage space under wood roofing

More Information about Roofing Materials, Methods, Standards

Asphalt Roofing Manufacturers Association (ARMA) www.asphaltroofing.org

Cedar Shake and Shingle Bureau www.cedarbureau.org

Metal Roofing Alliance www.metalroofing.com

Tile Roofing Institute www.tileroofing.org

-- Adapted with permission from Best Practices Guide to Residential Construction.

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

HTML Comment Box is loading comments...

Recommend / Share this Article

...

Technical Reviewers & References

InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

BEST PRACTICES GUIDE to Residential Construction
BEST ROOFING PRACTICES

METAL ROOFING
  ALUMINUM ROOFING
  Aluminized Steel Roofs
  Barn Roofing, Metal
  COPPER ROOFING
  Corrugated Metal Roofing
  Enameled steel roofing
  Galvalume Metal Roofing
  GALVANIC SCALE & METAL CORROSION
  Galvanized Steel Roofing
  LEAD in ROOFING, EFFECTS
  LIFE EXPECTANCY of METAL ROOFS
  METAL ROOF COATINGS & PAINTS
  METAL ROOF EXPOSED FASTENER SYSTEM
  METAL ROOF EXPOSED FASTENER FLASHING
  Metal Shingle Roofs, Embossed, Antique
  Metal Roofing Sources & Manufacturers
  METALS USED IN ROOFING
  MODULAR METAL ROOF SHINGLE SYSTEM
  NOISE TRANSMISSION in ROOFS
  SNOW GUARDS on SLATE & METAL ROOFS
  Soldered Flat Shingle and Flat Copper Metal Roofs
  Stainless Steel Roofing
  STANDING SEAM METAL ROOF INSTALLATION
  TERNE METAL ROOFING
  Zinc Metal Roofing

ARMA - Asphalt Roofing Manufacturer's Association - http://www.asphaltroofing.org/
750 National Press Building, 529 14th Street, NW, Washington, DC 20045, Tel: 202 / 207-0917
ASTM - ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA, 19428-2959 USA The ASTM standards listed below can be purchased in fulltext directly from http://www.astm.org/
Cedar Shake & Shingle Bureau, CSSB, U.S.: Sumas, WA 98295-1178, Tel: 604-820-7700, In Canada: Cedar Shake and Shingle Bureau #2 - 7101 Horne Street, Mission, BC V2V 7A2 Tel: (604) 820-7700, E-mail: info@cedarbureau.com , website: http://www.cedarbureau.org/
Forest Products Laboratory, US FPL, One Gifford Pinchot Drive, Madison, WI 53726, Tel: (608) 231-9200, Email: mailroom_forest_products_laboratory@fs.fed.us608-231-9200, website: http://www.fpl.fs.fed.us/
NRCA - National Roofing Contractors Association - http://www.nrca.net/, 10255 W. Higgins Road, Suite 600, Rosemont, IL 60018-5607, Tel: (847) 299-9070
UL - Underwriters Laboratories - http://www.ul.com/
2600 N.W. Lake Rd.
Camas, WA 98607-8542
Tel: 1.877.854.3577 / Fax: 1.360.817.6278 E-mail: cec.us@us.ul.com

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, and from the InspectAPedia bookstore. The 2010 edition of 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.

Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for this article. All rights and contents are ©Journal of Light Construction and may not be reproduced in any form.
Copper Roofing, by CDA
Copper Roofing, Master specifications for copper roofing and sheet metal work in building construction: Institutional, commercial, industrial, I.E. Anderson, 1961 (hard to find)
Corrugated Iron, Building on the Frontier, Simon Holloway
Low Slope Roofing, Manual of, 4th Ed., C.W. Griffin, Richard Fricklas, McGraw-Hill Professional; 4 edition, 2006, ISBN-10: 007145828X, ISBN-13: 978-0071458283
- Roof failure causes in depth (and specific methods for avoiding them)
- Roof design fundamentals and flourishes, based on voluminous industry research and experience
- New technologies and materials -- using them safely and correctly
- Comprehensive coverage of all major roofing systems pecifications, inspection, and maintenance tools for roofing work
Metal Roofing, an Illustrated Guide, R.A. Knowlton , [metal shingle roofs],
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
...

Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

A Comparison of Metal Choices for Roofing Systems

Aluminized Steel Metal Roofing System Properties

Aluminum Metal Roofing System Properties

Copper Roof Metal Roofing System Properties

Galvanized Steel Metal Roofing System Properties

Galvalume® Metal Roofing System Properties

Stainless Steel Roofing System Properties

Sources of Stainless Steel Roofing Products

Zinc Metal Roofing System Properties

Resources: Roofing Materials & Equipment Suppliers

Where to Buy Metal Roofing: Manufacturers & Metal Roofing Sources, Associations

Metal Roofing

Venting Underlayments

More Information about Roofing Materials, Methods, Standards

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair