Metal roofing examples (C) Daniel Friedman Standing Seam Metal Roof Systems
     

  • STANDING SEAM METAL ROOF INSTALLATION - CONTENTS: Standing seam metal roof systems. Installation guide standing seam roofing. Flashings and Accessories for Standing Seam Metal Roofs. Snow guards or snow brakes on metal roofs. Best practices for standing seam metal roofs
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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 panels.

The ribs overlap and lock together, concealing the fasteners and giving the roofing its name.

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Standing-Seam Metal Roofing Installation Practices & Details

Metal roofing examples (C) Daniel FriedmanAdapted/paraphrased with permission from Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES:

The hidden 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 available.

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.

Figure 2-42: Standing seam metal roof fasteners (C) J Wiley, S Bliss

  • 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 seams.

    [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 conditions.
  • 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

Metal roofing examples (C) Daniel FriedmanOn 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 ability.

Install the felt with plastic cap nails rather than metal buttons, which can cause corrosion when in contact with the roofing panels.

See GALVANIC SCALE & METAL CORROSION.

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.

Later, the 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.

Traditional standingseam 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?

Standing seam reroof over wood shingles (C) Daniel Friedman

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

Figure 2-41: Metal Roof Flashing details (C) J Wiley, S Bliss

[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.

Temporary roof vent flashing while waiting for metal roof installation (C) Daniel Friedman Eric Galow Permanent roof vent flashing for metal roof installation (C) Daniel Friedman Eric Galow

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.

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

Resources: Roofing Materials & Equipment Suppliers

Manufacturers

Metal Roofing Suppliers

  • 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
    [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: wintexinc@yahoo.com
    • DuraLok Roofing, (239) 449-0356 Fort Myers, FL USA
  • EDCO Products, website: http://www.edcoproducts.com/ (since 1946)
  • 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 Website: www.met-tile.com 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

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

  • Metal Roofing Alliance www.metalroofing.com

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?

Reply:

Jack,

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

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.

 

Continue reading at LIFE EXPECTANCY of METAL ROOFS or select a topic from the More Reading links shown below.

Or see SNOW GUARDS on METAL ROOFS for more examples of conditions and leaks on standing seam metal roofs.

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STANDING SEAM METAL ROOF INSTALLATION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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