Exposed Fastener Metal Roof Panel Systems InspectAPedia® -
Exposed fastener metal roof systems
Designs of panels used in exposed-fastener metal roofs
Set proper metal roof panel length to avoid buckling with exposed fastener systems
Proper metal roof exposed fastener type and location for exposed-fastener metal roof panels
Installation guide for agricultural building roofing or "metal barn roofing"
Characteristics of metal roofing materials: exposed fasteners, barn roofing, other exposed fastener roof systems
Best practices for exposed fastener metal roofing material installation, flashing, ventilation, nailing, underlayment
Questions & answers about exposed fastener metal roof systems: installation, troubleshooting, repair
This article explains the selection, applicability, and installation specifications for exposed fastener metal roof systems, also referred to as barn roofing, or agricultural building roof systems.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.
Because this roofing material is also sometimes used on residential buildings, homeowners and home inspectors should also review this material when diagnosing roof problems. 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 an exposed fastener roof on a utility building at the Summerblue Arts Camp, Two Harbors, MN.
Steel and aluminum panel roofing with exposed fasteners
has been a popular choice on agricultural buildings for
decades. In recent years, these “ag panels” have grown increasingly
popular for rural homes as well, since they can
provide a long-lasting roof at a cost comparable to asphalt
shingles. The products installed on homes, while essentially
the same material as the agricultural panels, generally use
better metal coatings, and installers pay more attention to
sealing and watertight detailing.
While a carefully installed exposed-fastener roof
should be free of leaks upon completion, small installation
errors can result in leakage later as the metal panels
undergo normal thermal movement that places stress on the
fasteners. With so many exposed holes in the panels, periodic
inspections are recommended. Also, the exposed
fastener heads, in addition to lending a rural look to the
building, tend to catch leaf debris and restrain sliding snow.
Materials used in Exposed-Fastener Metal Roofs
Exposed-fastener panels are typically 26 to
29 gauge, compared to the heavier 22 to 26 gauge used in
standing-seam roofing.
The ribs in exposed fastener roofing
are also lower and closer together than in standingseam
roofing and may be squared, rounded, or v-shaped
(see Figure 2-36).
Most exposed fastener or "barn roofing" panels are 2 to 3 feet wide and
formed with galvanized steel, Galvalume®, or aluminum.
Panel length. While some stock sizes are available,
ordering panels factory-cut to exact lengths simplifies
installation and reduces corrosion at field cuts.
Panels
can be ordered in any shippable length, although
excessive thermal movement can be a problem for steel
panels longer than 40 feet or for aluminum panels
longer than 16 feet.
Reduce Metal Roof Panel Lengths To Avoid Buckling
In regions with very wide temperature
swings, contractors should use shorter lengths - see “Thermal Expansion” in Table 2-10, shown just below. [Click any image or table to see an enlarged view.]
Installation Methods for Exposed-Fastener Metal Roofs
While traditionally installed over battens,
most panels in residential installations are now installed
over a solid plywood deck with minimum No. 30 felt underlayment.
Metal roofing manufacturers recommend plywood
over oriented-strand board (OSB) due to plywood’s
better screw-holding ability. Roofing felt should be installed
with plastic cap nails rather than metal buttons,
which can deteriorate the metal roofing by galvanic action
(see GALVANIC SCALE & METAL CORROSION).
Our exposed-fastener metal roof installation shown at above-left is located in Molde, Norway.
Align the metal roof panel to eaves. After installing drip edges and valley
flashing, the first panel is fit along one rake, square to
the bottom edge of the roof. If the roof is not square,
the first panel may need to be cut at a bevel along the
rake. Start at the downwind end of the roof, so the
edge of each overlapping panel faces away from the
prevailing winds.
Cutting exposed fastener metal roof panels. Where panels need to be cut, use snips
or shears rather than an abrasive blade, which overheats
the steel coatings and leaves a rough edge prone
to rust. Abrasive blades also produce hot metal filings
that can embed in the paint and cause rust on the face
of the panels.
Side and end laps on exposed fastener metal roofs. After the first panel is screwed
down, the next panel is set in place, lapping over the
first. Side laps are typically sealed with butyl tape and
held together with gasketed sheet-metal screws.
Where more than one panel is used up the run of the
roof, the upper panel laps the lower by 6 inches and is
sealed with butyl tape.
Fasteners used on exposed-fastener metal roofs.
Fasteners are typically special wood
screws with integral EPDM or neoprene gaskets that
compress under the screw head to seal the hole.
Fasteners should be driven at a right angle to the roof
plane and should be snug but not so tight as to deform
the washer (see Figure 2-37 above). Nearly all manufacturers
recommend placing screws in the flat sections
between ribs.
Although making holes in the flat section
may seem unwise, placing screws in the ribs is
discouraged for two reasons - check out our photo at left.
First, the long exposed
screw shaft passing through the rib is prone to snap
over time due to thermal movement of the panels.
Second, it is easy to overdrive the screws and crush
the panels.
Higher-cost EPDM washers are less likely
to leak than neoprene.
Take a closer look [click to enlarge] at fastener location and the "too-tight" bolting on the exposed fastener metal roof on this Minnesota building. Compare this roof installation to the Norway metal roof shown above.
Reroofing Using Exposed Fastener Metal Roof Panels
Panels can go directly over a single layer of
asphalt shingles in good condition. If the shingles are
curled or uneven, install 2x horizontal purlins at 16 inches
on-center. In either case, put down a new layer of No. 30
underlayment before installing the panels.
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
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.
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.
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.
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.
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
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).
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
"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
Mobile View
