Architectural Building Components


Metal, most often Galvalume steel, is consistently chosen as the roof material for projects with roof slopes of 1/2:12 or greater. There are several forms and styles of metal roofing; the most common are the vertical standing seam roof design. Standing Seam Metal Roof Panel Systems have proven to be an extremely effective and long lasting material choice when installed properly.

McElroy Metal manufactures both Hydrostatic Metal Standing Seam Roof Panel Systems as well as Hydrokinetic Roof Systems.

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There are four unique styles of metal standing seam panels:

Double Lock Seam Symmetrical Seam One Piece Interlock Two Piece Interlock
  1. Mechanically seamed Hydrostatic Panels – or Structural Standing Seam Metal Roof require that the two standing seam panels to be engaged with a mechanical seaming tool (examples below). Structural metal standing seam panel systems offer superior wind uplift resistance and can be curved or tapered.
  2. Symmetrical Mechanically Seamed – This style of SSMR is the newest, most innovative option available. It combines the weathertight benefits of the mechanical seam with the replacement options of a two-piece snap-lock panel. Unlike the typical “directional” mechanically seamed panels, the two-piece symmetrical standing seam panels, such as 238T, can be installed using fixed clips while still allowing for thermal movement. Combining the advantages and eliminating the disadvantages involved with the various metal roof standing seam options, the two-piece mechanical seam panel is the best option for almost any roof design. It can be curved and is easily tapered due to its symmetrical design. Lastly, this style of standing seam metal roofing has demonstrated an ability to withstand uplift pressures well in excess of the one-piece structural standing seam panel.
  3. One Piece Snap-Lock – This style of metal roof panel requires two panel seams to snap together. The direct attachment of the roof panels simulates the look of a mechanically seamed panel without the additional operation of seaming. These metal roofing panels, despite their various structural capabilities, are best suited for decked applications with slopes of 3:12 and greater. Snap-lock standing seam is less likely to be used in high wind uplift areas. This is due to the fact that more clips and attachment points are required to satisfy uplift pressures. In many instances, corner pressures (the most demanding) cannot be satisfied. This has frequently proven to be the location where roof failure occurs in windstorms. As the capabilities of structural standing seam increase and building code requirements become more stringent, the demand for this style of standing seam metal roofing has deteriorated.
  4. Two Piece Snap-Lock – This style of metal roof requires both a panel and a cap or batten. The cap or batten unites two panels by snapping down onto a butterfly clip (example above) While these panels offer very little structurally and require a solid deck with a premium underlayment for installation, they are easier to install on roofs with valleys and hips- due to their ability to be installed bi-directionally. The simplicity of the panel shape lends themselves to curved and tapered roof designs. As the capabilities of symmetrical structural standing seam increase, the demand for this style of metal roofing has deteriorated.

What makes a good standing seam panel?

A good standing seam panel is one that is capable of satisfying the design criteria and building codes. Consult a metal roofing manufacturer, like McElroy Metal, about the capabilities of the metal roof panel prior to specifying it. Once the proper metal roofing product has been selected, the next critical step is proper installation.

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Metal, like other roof materials, is vulnerable to thermal movement- expansion and contraction. Thermal Movement must be a central thought of “detailing” a standing seam metal roof system. The entire success of standing seam metal roofing to handle thermal movement can be negated by a single fastener going through a single panel. Consult McElroy Metal about providing shop drawings or details for your next project with standing seam.

Quality assurance measures for standing seam metal roofing:

  1. Provide continuous Length Panels (No laps)
  2. Avoid unnecessary end laps in trim, specifically valleys and transition trim.
  3. Provide a standing seam metal roof panel that offers individual panel replacement
  4. Consider alternative solutions for curb installation to ensure minimal maintenance on your standing seam roof

Metal Roofing