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Standing seam metal roofs:
This article explains the proper installation, fastening, and flashing details for standing seam metal roofs. Standing-seam roofing consists of individual panels that
run the length of the roof with a high rib up each side of
The ribs overlap and lock together, concealing
the fasteners and giving the roofing its name.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Standing-Seam Metal Roofing Installation Practices & Details
fasteners allow thermal movement in the panels and are
less likely to leak than exposed fasteners. However, some
trim pieces are still fastened with exposed screws.
The smooth surface of a standing-seam roof provides
a cleaner appearance and is easier to keep clear of leaf debris
than tile, wood, or other textured roofing surfaces.
Also, it can be walked on when necessary. Snow slides off
easily as well, making this a popular choice in high snow
regions. The cost is generally 25% to 50% more than an
exposed-fastener roof of similar materials.
Materials Used in Standing Seam Metal Roofs
Standing-seam panels are 8 to 24 inches wide
and available in steel, copper, and aluminum with a wide
array of finishes (discussed below). Stiffening ribs may
be added to wider panels to reduce waviness (oil-canning).
Thicknesses for quality residential applications are typically
24 or 26 gauge, but lighter and heavier stock is also
Standing seam metal roof installers can form panels on-site from coil stock
with portable roll-forming equipment, or they can order
factory-made panels from a growing number of metal roofing
manufacturers. Most factory-made panels have snaptogether
seams, eliminating the need for special crimping
equipment used by site fabricators. In most cases, panels
are fabricated to run from eaves to ridge, eliminated the
need for end lap joints.
Clips vs. flange standing seam roof panel fastening methods. Standing-seam panels either have
an integral screwing flange (through-fastener panels)
or are installed with clips placed 20 to 24 inches
on-center (Figure 2-42).
Clip systems are more costly
to manufacture and to install, but they have better
wind resistance and a higher water-lock at the
[Click to enlarge any image]
Also, because the clips allow unlimited panel
movement, panels can be fabricated to any length.
The flange type should be limited to 40 feet for
steel and 20 feet for aluminum for normal climate
Site vs. factory fabrication of standing seam metal roof panels. For those with the equipment,
site fabrication provides flexibility and saves on
shipping costs, which can be high.
Site fabricators can
also produce matching flashings and accessories to
match the specific needs of the job. Factory-made
panels, on the other hand, offer consistent quality, as
well as preformed flashings and fittings that simplify
installation. Using factory-produced panels, however,
requires detailed planning since every piece of roofing
must be preordered to length.
Installation Specifications for Standing Seam Metal Roofs
On new homes, most panels are installed
over a solid plywood deck with minimum No. 30 felt
underlayment. Metal roofing manufacturers recommend
plywood rather than OSB due to plywood’s better screwholding
Install the felt with plastic cap nails rather
than metal buttons, which can cause corrosion when in
contact with the roofing panels.
After installing the drip edge, install the first panel,
making sure it is square to the bottom edge of the roof. If
the roof is not square, pull the panel away from the rake so
the first rib does not overhang the rake edge.
rake trim piece will cover any small discrepancies. If the
panels have an integral screw flange, keep the screws just
snug so the panels can move with temperature changes.
The clips are designed to allow thermal movement.
The next panel fits over the first with an overlapping
rib. Fit each panel to a line snapped up the roof, marking
the edge of each panel. Without layout lines, the panels
can build up an incremental error, throwing off the layout.
As panels are installed and secured, the joints are easily
locked together with hand pressure.
roofing required special motorized crimpers to lock
the seams. While these are still used on some low-slope
systems, most residential installations now use snap-together
panels. Unless the layout works perfectly, the last
panel will need to be cut along the opposite rake and bent
with a hand seamer to form the end rib.
Reroofing Using Standing Seam Metal Roofs Over Other Roof Coverings?
Our standing seam barn roof re-roof photo (left) demonstrates that re-roofing with standing seam metal roofs over older buildings is a very old practice.
In this case the barn roof originally was covered with wood shingles, installed when the barn was constructed in the late 19th century in upstate New York.
Many installers will not install standing-seam
roofing over existing asphalt shingles since the rough surface
will tend to bind the panels and cause “oil-canning,” as
the panels move with temperature changes.
One option is to
install the new metal roofing over 2x4 purlins nailed
through the old roofing and shimmed to form an even plane.
Follow manufacturer’s recommendations for spacing of
purlins, typically no more than 24 inches on-center.
Flashing and Sealing Details for Standing Seam Metal Roofs
[Click to enlarge any image]
Typical standing seam metal roof flashing details are similar to those found in Figure 2-41 shown at left .
Manufacturers of preformed
roofing panels provide eaves and rake flashings, ridge
caps, and sidewall flashings in matching finishes, as well
as coil stock for site fabrication.
Many flashings are
designed with hidden fasteners; others require exposed
gasketed screws. If you want to see the original installation details for the plumbing vent shown at above right, take a look at the photos and text at the bottom of our article On PLUMBING VENT DEFECTS & NOISES.
Follow manufacturers’ recommendations regarding which sealants to use for compatibility with the roofing (typically butyl tape, or gunnable terpolymer butyl or urethane sealant).
In general, avoid acid-cure silicone (the type that smells like vinegar) as it can be corrosive to many metal finishes.
Modular metal shingle, tile, and standing-seam panels
Modular metal shingle panels and standing seam panels
Modular metal shakes and standing seam panels
Decra Roofing Systems
Modular metal shingle, tile, and shake panels
Dura-Lok Roofing Systems
Modular metal roofing shingles with granular coating
[Reader comment suggests this company may no longer be in business - Ed. Somewhat curious remark as we found the contact information listed below in January 2015]
Dura-Lok Roofing Systems, Wintex Industries, 17221 Alico Center Road
Fort Myers, FL 33967, (since 1986), Website: duralocroofingsystems.com/and Email: firstname.lastname@example.org
DuraLok Roofing, (239) 449-0356 Fort Myers, FL USA
Exposed fastener and concealed clip metal roofing
Gerard Roofing Technologies
Modular metal shake and tile panels with granular
Modular metal roof-tile panels
Metro Roof Products, Website: http://www.metroroofproducts.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
Cedar Breather, a
3/8 -in.-thick matrix-type underlayment
designed to provide ventilation and drainage space under
More Information about Roofing Materials, Methods, Standards
Metal Roofing Alliance
Standing Seam Metal Roof Seam Heights
Reader Question: 20 January 2015 Jack said:
What should be the minimum height of the standing seam for a 1.5"/12 roof?
The flange system metal roof is typically made with a seam height of 1 1/4" - also referred to as "Eco" seam by some manufacturers.
Flat or "Dutch" or locking type standing seams range in height from a low of about 1" to 2 3/8" with taller seams generally used on lower slopes.
For relatively low slopes like the 3:12 you cite you may need to go to the higher seam height to protect against leakage, especially in a snow-climate. For roofs you describe that are as low slope as 1.5 in 12, in a snow climate where there is risk of ice dams I I question if a standing seam roof would be recommended by some manufacturers.
But Atlas Roofing describes standing seam roofing products used for low slope roofs described as sloped to 2:12 or less over solid substrate. These roofs are covered with a locking type standing seam that is 2 3/8" in height.
OPINION: Watch out: even with a tight, tall locking standing seam roof, if your low -slope roof is subject to ice dams, snow blockage or any other condition that could cause water backup-s on the roof such that the water depth can ever exceed the seam height you can expect leak trouble.
You can contact Atlas International, an Allentown PA USA company at (610) 395-8445 or at www.atlas.com
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(Feb 3, 2012) New Metal Suppliers - Update said:
Hi, You ought to consider updating your metal roofing suppliers. I think DuraLoc is out of business. Players not included are Metro Roof Products and EDCO Products....both good, well distributed firms.
Question: underlayment for metal roofs installed atop existing roof surfaces?
AUTHOR:Anonymous (no email)
COMMENT:We have a project which has a steel truss roof system with a structural metal deck diaphragm (B deck type for seismic requirements)installed over the steel trusses.
We want to provide a standing seam roof over the structural metal deck. Slope is 3:12 and the attic is a cold attic. Do we have to provide any underlayment between the structural deck and the standing seam roof? Or can we just install the standing seam roofing directly over the structural deck. (The structural deck grooves are running perpendicular to the slop of the roof). Any assistance for the best installation procedures will be appreciated. You can reply to this e-mail: email@example.com.
You will probably need to install underlayment - being safer against galvanic or other corrosive problems and you might need more. Here are some example specifications from Best Buy Metals - bestbuymetals.com but you will want to check the installation specifications for the specific brand you are buying.
Also check standing seam height alternatives. For relatively low slopes like the 3:12 you cite you may need to go to the higher seam height to protect against leakage, especially in a snow-climate.
Standing Seam is designed to be installed over solid decking.
Make sure any existing decking is smooth, level and in good condition. Replace any decking not meeting those requirements.
In most cases Standing Seam can be installed over existing shingles. Check local building codes to confirm this is possible in your area.
If installing over existing shingles, we recommend the use of 30 lb felt or synthetic
underlayment over the shingles first to keep the rough side off the shingles off the backside of
Here is another example specification from the Summit Pacific metal sales standing seam roof installation guide:
After verifying that the roof is true and square, the roof deck is ready for underlayments. A 30#
asphalt saturated felt underlayment is recommended, and should be used in conjunction with rubberized ice and water
shield type membranes as necessary.
Apply underlayments starting at the eave of the roof, and continue upwards to the top of the roof, and over the ridge or nosing, or up the endwall.
Do not allow underlayments to be exposed for prolonged periods of time, as they may wrinkle and warp, creating an uneven substrate that may telegraph through the metal roofing panels.
Question: can I add just partial snow guards on my metal roof?
(Oct 31, 2014) Mary said:
I've had a standing seam metal roof for about 3 years, without any snow guards, on my ranch-style home in central NY. Now, with my nearly deaf mother living with me, I want to add the guards over the porch to protect her when she takes her dog out. Is there a problem with just doing the limited application rather than full coverage? Thank you.
We see lots of metal roofs on which installers provided snow guards ONLY over entrances or other spots where there is extra risk. As long as snow falling off of other sections of the roof are not going to cause trouble, your approach is fine.
"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: firstname.lastname@example.org,
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 email@example.com 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.
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:
"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
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