Exposed Fastener Metal Roof Panel Systems
- METAL ROOF EXPOSED FASTENER SYSTEM - CONTENTS: 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
- POST a QUESTION or READ FAQs about exposed fastener metal roof systems: installation, troubleshooting, repair
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Metal roof installation:
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. 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.
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Exposed-Fastener Panels for Metal Roof Installations
Adapted/paraphrased with permission from Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:
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
[Click to enlarge any image] At left is an exposed metal faster roof on a barn in Dutchess County, New York, in the U.S.
The metal roofing 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
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.
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.]
[Click to enlarge any image]
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
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
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
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.
-- Above material on exposed metal fastener roofing installation procedures was adapted with permission from Best Practices Guide to Residential Construction.
Exposed Fastener Metal Roofing Fastener Spacing Schedule
Roofing manufacturers (such as Fabral in the U.S. and Dimond in New Zealand) give installation specifications for their product including screw fastener spacing schedules (and other data such as unsupported spans, unsupported overhang, and different fastener types).
Typically the fastener spacing is specified as number of fasteners per square (say 75 or 80 fasteners) but an allowance must be made for more fasteners when installing exposed fastener metal roofs in high wind zones.
Details of metal roof fastener spacing distances or schedules along with photo examples are provided in a the next article in this series, found at
METAL ROOF EXPOSED FASTENER SPACING
Resources: Roofing Materials & Equipment Suppliers
[Bold faced roofing suppliers in the list below provided technical information quoted or adapted in the article above - Ed.]
- Atas International
Modular metal shingle, tile, and standing-seam panels
- Classic Products
Modular metal shingle panels and standing seam panels
- Custom-Bilt Metals
Modular metal shakes and standing seam panels
- Dimond Roofing Systems, Tel: 0800 DIMOND, Website: http://www.dimond.co.nz The company has offices throughout both North Island and the South Island of New Zealand, of which we give just a few
Dimond Roofing Systems, Auckland,
48 Victoria St, Onehunga,
New Zealand, Ph: 09 634 0575 Fax: 09 634 6231
Dimond is New Zealand's largest manufacturer of steel roofing, cladding, structural and rainwater goods.
Dimond Roofing Systems, Christchurch,
89 Buchanans Rd, Hornby,
Ph: 03 336 0045 Fax: 03 342 3670
Dimond Roofing Systems, Whangarei,
33 Rewarewa Rd,
Ph: 09 438 1539 Fax: 09 438 6525
- Decra Roofing Systems
Modular metal shingle, tile, and shake panels
- Dura-Lok Roofing Systems
Modular metal roofing shingles with granular coating
- Fabral Corporation:
Lancaster PA, USA, www.fabral.com
Tel: 800-477-2741, Exposed fastener and concealed clip metal roofing
- Gerard Roofing Technologies
Modular metal shake and tile panels with granular
Modular metal roof-tile 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
Cedar Breather, a
3/8 -in.-thick matrix-type underlayment
designed to provide ventilation and drainage space under
Metal Roofing Materials, Methods, Standards
Metal Roofing Alliance
Continue reading at METAL ROOF EXPOSED FASTENER SPACING or select a topic from the More Reading links shown below.
Or see SNOW GUARDS on METAL ROOFS
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Technical Reviewers & References
Publisher's Google+ Page by Daniel Friedman
Click to Show or Hide Citations & References
- Fitzmons, Tom, "How windy is Wellington, really?", (2011), retrieved 9/25/14, original source http://www.stuff.co.nz/dominion-post/capital-life/6111069/How-windy-is-Wellington-really
- 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.
- "Choosing Roofing," Jefferson Kolle, January 1995, No. 92, Fine Homebuilding, Taunton Press, 63 S. Main St., PO Box 5506, Newton CT 06470 - 800-888-8286 - see http://www.taunton.com/FineHomebuilding/ for the magazine's website and for subscription information.
-  Follansbee Roofing, Follansbee WV 26037, Tel: 800-624-6906, website: www.follansbeeroofing.com and http://www.follansbeeroofing.com/products/TerneII.aspx Quoting Follansbee on TerneII properties:
Follansbee Steel is the only manufacturer of a pre-painted or natural Terne roof and is a leading supplier of metal roofs for new and retrofit commercial, institutional, residential and historic preservation projects.
Terne II - Classic Terne-Coated Steel
... is a new and improved version of historic Terne metal, ... Terne II has improved capability for resisting corrosion in all environments ... also has excellent formability, solderability, and affinity for paint ... without compromising mechanical characteristics. It can be used in flatlock, standing seam, vertical wall designs and virtually any other application in which original Terne has been used. It is strong and ductile, having high yield and tensile strengths as well as workability. This new material can easily be formed with conventional roofing tools.
With Terne II roofing, it is advisable to paint the material as soon as conditions permit. Oxide formation is slower than with the original Terne and the wait for proper painting conditions provides substantially less risk. The new material is coated with Follansbee's new ZT® alloy, a combination of zinc and tin. This coating is designed not only as a barrier but also to be anodic to the steel substrate and reduce the potential for oxidation before painting.
The traditional oil-based paints long required on original Terne are not recommended for application on Terne II. Follansbee's Rapidri paint with its faster drying time and ease of application is much superior to the old painting system. The Rapidri acrylic paints are aesthetically pleasing while offering enhanced durability and color retention. ...
- Metal Roofing Alliance, E. 4142 Hwy 302, Belfair, WA 98528, Telephone:(360) 275-6164, Customer Support 410-534-6900, Email: email@example.com,
Website: www.metalroofing.com. Quoting:
The Metal Roofing Alliance was formed in 1998 by a small group of forward-thinking metal roofing manufacturers with the main goal of educating consumers about the many benefits of metal roofing. Since our inception, we've shown millions of people just how beautiful, durable and money-saving metal roofing can be for them. Over the years, our membership has grown to include paint companies, material suppliers, industry publications and more. Be sure to take advantage of all of the great resources our members offer.
- The Metal Initiative, 4700 W. Lake Ave., Glenview, IL 60025, P:847.375.4785 Website: www.themetalinitiative.com/, Email: Louise Ristau firstname.lastname@example.org Quoting:
The Metal Initiative is a coalition of manufacturers, individuals and associations that have come together to provide information on the features and benefits of metal in construction. Carrying its message of metal primarily to the professional building owner community, The Metal Initiative seeks to gather and disseminate useful information for decision-makers.
- Metal Roofing, an Illustrated Guide, R.A. Knowlton , [metal shingle roofs],
- 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
- Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used)
- Grapevine Design Guidelines - Web Search 07/12/2010
- "Copy on file as - /roof/Asbestos-to-Zinc_Metal_Roofing_NPS.pdf - From Asbestos to Zinc, Roofing for Historic buildings, Metals - ", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
- "Copy on file as - /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_3.pdf - From Asbestos to Zinc, Roofing for Historic buildings, Metals-part II, Coated Ferrous Metals: Iron, Lead, Zinc, Tin, Terne, Galvanized, Enameled Roofs - ", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
- "On file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_2.pdf - From Asbestos to Zinc, Roofing for Historic buildings, Metals- Roofing Today - ", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
- "Copy on file as - /roof/Roofing_Historic_NPS.pdf">Roofing for Historic buildings - ", Sarah M. Sweetser, Preservation Brief 4, Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
- "Copy on file as - /exterior/NPS_Preserv_Brief_16_Subs_Mtls.pdf">The Use of Substitute Materials on Historic Building Exteriors - ",
Sharon C. Park, AIA, Preservation Brief 16, Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
- 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
- "Metal Roofing: 'Fixing' for Thermal Movement [ copy on file as /roof/Metal_Roof_Movement_NRCA.pdf ] - ", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 72, NRCA
- "Metal Roof Systems: Design Considerations for Snow and Ice [ copy on file as /roof/Metal_Roof_Snow_Ice_NRCA.pdf ] - ", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 74, NRCA
- "Steel [Roof] Decks: Issues for the 1990's [ copy on file as /roof/ Steel_Roof_Deck_Corrosion1_NRCA.pdf ] - ", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 74, NRCA
- "Steel [Roof] Deck Corrosion Bulletin, NRCA [ copy on file as /roof/Steel_Roof_Deck_Corrosion_NRCA.pdf ] - ", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] p. 58, NRCA
- "The Many Aspects of Metal [Roof] Shingles [copy on file as Metal_shingles_NRCA.pdf ] - ", Thomas L. Smith, AIA, CRC., Professional Roofing, [date pending] NRCA
- 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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