Flashing & Sealing Specifications for Exposed Fastener Metal Roof Systems
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How to install flashing on barn roofing
How to seal barn roofing
Exposed fastener metal roof systems
Installation guide for agricultural building roofing or "metal barn roofing"
Flashings and Accessories for Exposed-Fastener Metal Roofs
Characteristics of metal roofing materials
Best practices for roofing material installation, flashing, ventilation, nailing, underlayment

This article describes metal roof flashing and sealing products and installation details for exposed-fastener metal roof systems: barn roofing, or agricultural building roofing 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 METAL ROOF EXPOSED FASTENER SYSTEM and METAL ROOF COATINGS & PAINTS and GALVANIC SCALE & METAL CORROSION. See our metal roofing home page, METAL ROOFING and see CORRUGATED ROOFING and COPPER ROOFING.

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Flashings and Accessories for Exposed-Fastener Metal Roofs

Adapted/paraphrased with permission from Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:

Most manufacturers supply preformed flashings, drip edges, rake moldings, and ridge caps color-matched to their roofing panels, as well as color-matched coil stock for fabricating custom pieces onsite. They also provide rubber closure strips or expandable foam tapes to seal panel ends against water and insect intrusion at eaves, valleys, ridges, and other terminations.

Figure 2-38: metal roof panel end treatment (C) J Wiley, S Bliss

Pay particular attention to panel ends at metal roof valleys. Some manufacturers supply special closures for the angled cuts through ribs, but closures may need to be fashioned by cutting up standard closure strips.

Some manufacturers also provide an expandable foam sealant tape that conforms to the rib pattern for a tight seal up the valley.

Depending on the panel profile, the end treatment will vary, but ends should be fully sealed. Remember to place screws in flat sections and to use extra screws up the valley (Figure 2-38).

Figure 2-39: metal roof panel ridge vent (C) J Wiley, S Bliss

For a metal roof vented ridge, place short sections of a matrix-type ridge vent between the ribs and secure with a preformed metal cap (Figure 2-39).

Also see ROOF VENTILATION SPECIFICATIONS.

Figure 2-40: metal roof panel plumbing vent flashing (C) J Wiley, S Bliss

For plumbing vents, most manufacturers recommend a moldable aluminum jack bent to conform to the profile of the roofing (Figure 2-40).

Rectangular openings, such as skylights and chimneys, typically require both base and counterflashing so roof panels are free to move with changes in temperature.

Depending on the panel profile, either use a pan flashing or an L-flashing sealed to the top surface of the roofing panel with sheet metal screws and butyl tape.

On large openings in metal roofs, a cricket is needed on the up slope to divert water around the penetration. Custom-made, one-piece curbs with built-in diverters simplify this type of installation. All flashing joints should be sealed with butyl tape or a manufacturer- recommended sealant.

Sealing Details for Exposed-Fastener Metal Roofs

For the watertight performance required on homes (as opposed to barns), metal roofs need careful sealing around all penetrations, side laps, and end laps. On side seams and lap joints, the sealant should always go on the uphill, or “dry,” side of any fasteners (Figure 2-41). Sealant should also be used at ridge caps, valleys, and wherever flashings lap over or under the metal roofing.

Figure 2-41: metal roof panel flashing (C) J Wiley, S Bliss

The preferred sealant for most concealed seams in metal roof panels is butyl tape, which absorbs movement and will not shrink. Gunnable terpolymer butyl or urethane caulk can also be used, as specified by the manufacturer. But never use acid-cure silicone caulking (the common type with vinegar odor) or asphalt roofing cement, as they will damage most metal coatings.

How to Allow for Panel Movement in Exposed Fastener Metal Roof Systems

Metal roof panels were originally designed for installation on purlins that can absorb the normal movement as the panels expand and contract from temperature changes. The thermal movement of a long panel installed over solid plywood, however, can cause problems.

Typically, either the hole in the metal roofing elongates—creating a potential leak—or the screw becomes loosened, making the roof vulnerable to blow-off. The problems are greatest with aluminum, which has 70% more thermal movement than steel and less tensile strength. To avoid problems, experts recommend the following:

With exposed-fastener panels, avoid lengths over 40 feet for steel or 16 feet for aluminum—less for climates subject to wide temperature swings. Break the run into two panels.
On long runs of painted roofing, choose lighter shades, preferably white.
Use screws in the flat part of the panel, not on the ribs. Screws should penetrate the sheathing fully, plus 1/4 to 1/2 inch.
Where leak-free performance is critical, fasten the roofing to Z-shaped metal purlins screwed horizontally across the plywood sheathing. Or switch to a concealed fastener system.

Also see "Metal Roofing: 'Fixing' for Thermal Movement", Thomas L. Smith, AIA, CRC

Wavy Metal Panels or Oil-Canning Problems on Metal Roofs: Thermal Expansion

Thermal expansion in light-gauge metal panels can cause a wavy appearance called “oil-canning” in the flat areas. In general, this does not signal a performance problem, but it may be visually objectionable.

Oilcanning tends to be most visible in bright light from a close distance, and it is generally more noticeable on shiny metals, such as Galvalume®, than on colored metal panels.

Oilcanning on metal roofs is primarily a problem in profiles with few ridges to stiffen the panels. To reduce the metal roof rippling or oilcanning effect, some manufacturers provide self-adhesive foam strips that are attached lengthwise to the bottom of metal panels.

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

Resources: Roofing Materials & Equipment Suppliers

Manufacturers

Metal Roofing

Classic Products www.classicroof.com Modular metal shingle panels 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
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
Atas International www.atas.com Modular metal shingle, tile, and standing-seam panels
Custom-Bilt Metals www.custombiltmetals.com Modular metal shakes and standing seam panels
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

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

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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.
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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 ROOF COATINGS & PAINTS
  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

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/
"Metal Roofing: 'Fixing' for Thermal Movement", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 72, NRCA
"Metal Roof Systems: Design Considerations for Snow and Ice", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 74, NRCA
"Steel [Roof] Decks: Issues for the 1990's", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 74, NRCA
"Steel [Roof] Deck Corrosion Bulletin, NRCA", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 58, NRCA
"The Many Aspects of Metal [Roof] Shingles", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] NRCA
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

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

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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.
Architectural elements: the technological revolution: Galvanized iron roof plates and corrugated sheets; cast iron facades, columns, door and window caps, ... (American historical catalog collection), Diana S Waite, available used out of Amazon.
Asphalt Roofing Residential Manual,
Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
Built-Up Roof Systems, Manual, C.W. Griffin, Mcgraw-Hill (Tx); 2nd edition (July 1982), ISBN-10: 0070247838, ISBN-13: 978-0070247833
Concrete Folded Plate Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author), Butterworth-Heinemann, 1998, ISBN-10: 0340662662, ISBN-13: 978-0340662663
Concrete Shell Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author),
Concrete Dome Roofs (Longman Concrete Design and Construction Series),
Concrete Roofing Tile, History of the, Batsford, 1959, AISN B000HLLOUC (availble used)
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
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
Handbook of Building Crafts in Conservation, Jack Bower, Ed., Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of Congress Catalog Card Nr. 81-50643.
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
Historic Slate Roofs : With How-to Info and Specifications, Tina Skinner (Ed), Schiffer Publishing, 2008, ISBN-10: 0764330012 , ISBN-13: 978-0764330018
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],
Patio Roofs, how to build, Sunset Books
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.)
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).
Slate Roofing in Canada (Studi4es in archaeology, architecture, and history),
Smart Guide: Roofing: Step-by-Step Projects, Creative Homeowner (Ed), 2004, ISBN-10: 1580111491, ISBN-13: 978-1580111492
Solar heating, radiative cooling and thermal movement: Their effects on built-up roofing (United States. National Bureau of Standards. Technical note), William C Cullen, Superintendent of Documents, U.S. Govt. Print. Off (1963), ASIN: B0007FTV2Q
Tile Roofs of Alfred: A Clay Tradition in Alfred NY
"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
Wood Shingle Roofs, Care and Maintenance of wood shingle and shake roofs (EC), Stanley S. Niemiec (out of print)
...

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Flashings and Accessories for Exposed-Fastener Metal Roofs

Sealing Details for Exposed-Fastener Metal Roofs

How to Allow for Panel Movement in Exposed Fastener Metal Roof Systems

Wavy Metal Panels or Oil-Canning Problems on Metal Roofs: Thermal Expansion

Resources: Roofing Materials & Equipment Suppliers

Manufacturers

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