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Posted by McElroy Metal ● Jul 15, 2021 3:00 PM

R-Panel Roofing vs. Standing Seam Roofing

There are many options available to building owners faced with choosing a new roof. Consequently, it is essential to find the right roofing system to meet the building’s longevity, durability, and aesthetic goals. Two options available to building owners for new construction and retrofits are R-Panel roofing and standing seam roofing.

What is R-Panel Roofing?

R-Panel is a generic industry term used for a metal roof or wall panel. Initially, R-Panels were used almost exclusively in the pre-engineered metal building industry.  Over time, however, R-Panel has also become quite popular for residential roofing, especially in the southwest. 

R-Panel sheets are 3’ wide with major ribs 12" on center. Installation involves penetrating the panel with a fastener into the substrate or structural members below.

It is important to realize that tens if not hundreds of different companies manufacture R-Panel. While they all produce a product that matches the basic specifications above, the quality levels are anything but similar.  

Two common differences to consider are panel gauge and paint system.  At McElroy Metal, we’re proud to offer our R-Panel in both 26 & 24 gauge and two different paint systems. We recommend our Kynar 500 paint system for projects with long-term performance requirements; however, we also provide a silicone-modified polyester system (SMP) for cost-sensitive projects.  If you aren’t familiar with the differences, you can learn more about the paint systems here.

Beyond paint systems and panel gauges, the quality of the actual roll-forming equipment can vary greatly.  While it might not seem obvious, tooling quality affects everything from panel appearance to ease of installation, and ultimately performance.  

Some smaller roll-formers (often called regional roll-formers) produce R-Panel from tooling that simply doesn’t offer the necessary panel length and width control.  Still, others struggle to match the crispness of the panel ribs that other more high-end manufacturers offer.  

Bottom line:  Unfortunately, not all R-Panels are created equal.  Consequently, it’s essential to ask questions regarding panel thickness, paint systems, and tooling quality before selecting a manufacturer for R-Panel products.

What is Standing Seam Roofing?


Standing seam metal roofs are typically installed vertically and run from eave to ridge. Standing seam systems typically feature a raised interlocking seam that connects adjoining panels together and is popular in commercial, residential, and industrial settings.

Standing seam systems are installed with hidden clips and fasteners, eliminating visible fasteners which are more prone to leaking over time. As a result, some standing seam systems often offer what is called a weathertightness warranty.  These warranties are designed to assure building owners that their building will remain leak-free for a specified period, often 20 years. 

Learn more about standing seam roofing.

R-Panel Roofing vs. Standing Seam Roofing

Cost Comparison

In comparing the two systems, it’s important to realize that R-Panel is widely available, often offers a shorter lead-time, and is more economical to purchase and install than standing seam systems. Part of the difference lies in the design differences between the panels. 

R-Panel covers 3’ where standing seam products more often cover 16-18”, which means that it takes two standing seam panels to cover the same square footage as one R-Panel.  Two panels vs. one affect everything from panel production at the manufacturer to packaging, transportation, and even crew installation, so the difference in panel width is significant. 

Additionally, R-Panels use exposed fasteners for attachment, where standing seam panels utilize clips and hidden fasteners.  While that difference might seem minimal, it definitely impacts cost.  The clip is an additional cost to standing seam systems, for starters, but clipped systems also install more slowly than an exposed fastener panel like R-Panel.

Durability Comparison

Given the higher product and installation costs,  you might be wondering why any owner would ever choose standing seam products over an R-Panel style. The downside of R-Panels is that expansion and contraction can cause the fasteners to “slot” over time and wear away a bit of the metal.  When this occurs, water can enter the building.  Once this happens, owners then choose to either replace the screws with an oversized fastener to cover the elongated hole or remove and replace the panels.  

slotted fastener

While that isn’t an ideal situation from either a cost or maintenance perspective, it is important to realize that expansion and contraction are functions of thermal cycling.  Consequently, the phenomenon is worse in areas of the country that experience large temperature swings.  It’s also noteworthy that panels under 40’ long aren’t typically affected by thermal cycling. So for building owners with panels below 40’ or those located in areas where temperature changes are minimal, it can be a non-issue.

Conversely, fasteners don’t pierce standing seam panels during installation.  Instead, a clip is commonly attached to the substructure, and the panels then engage with the clip. This clip allows for much greater expansion and contraction than what an R-Panel or any other exposed fastener panel can accommodate. Since there are no exposed fasteners in a standing seam roof system, thermal cycling (or expansion and contraction of the panels) doesn’t limit the system’s life expectancy.

Maxima Curved Metal Roof on High SchoolSummary

While standing seam systems cost more to purchase and install, many owners find the enhanced durability, reduced likelihood of leaks, and minimal maintenance worth the extra cost.

Standing Seam Systems

Throughout this article, we’ve referred to R-Panel and standing seam panels as two similar but different things.  But that’s really an unfair comparison.  R-Panel is a specific panel type where standing seam represents an entire product family.  

While standing seam products are similar in their attachment method, there are numerous different profiles and applications for standing seam panels. Although the different panel types can work on virtually any building that meets the required roof slope, there are certainly some more common products by industry segment.

Popular Residential/Light Commercial Products

Meridian Standing Seam Roof Panels RenderingMeridian:  Meridian is our most economically priced standing seam panel for projects with a solid deck and a minimum 3:12 slope.  The system is less expensive because fasteners attach the panel to the substrate through a pre-punched flange instead of clips. This product is also more economical since it’s produced from 26 gauge material instead of the heavier 24 gauge thicknesses typical for standing seam systems. Consequently, the Meridian product is popular for both residential and light commercial projects.

Medallion-Lok Roofing Panel RenderingMedallion Lok:  With a 1 ¾” rib height and in-seam sealant in the male/female leg, our Medallion Lok profile is also a favored product for residential and light commercial buildings.  Medallion Lok, produced in 24 gauge, offers purlin spanning capabilities, widths ranging from 12-18”, and in many cases, a weathertightness warranty.

Popular Commercial/Industrial Products

2_800x400238T: Our 238T panel is a symmetrical panel which means that the panel looks the same on both the right and the left side.  This design allows panel installation from either direction, which helps reduce installation costs and minimize scrap.  But perhaps the most significant advantage of a symmetrical panel system is that it offers individual panel replacement in the field of the roof.  Consequently, it is a top choice for owners who anticipate future building repairs, modifications such as curbs, or building expansions due to its symmetrical design and individual panel replaceability. Our 238T mechanically seamed system is available in various pan widths. Weathertightness warranties are commonly available for this panel type as well.

McElroy Metal Maxima Striated Standing Seam System RenderingMaxima:  Our Maxima series offers a wide variety of options, including 1.5, 2, and 3” seam heights.  Two of the heights (1.5” & 2”) can also be curved for radius applications. All of the various panel heights are mechanically seamed, and weathertightness warranties are commonly available.  With the vertical leg design, this panel offers an improved aesthetic appearance over trapezoidal panels like our ML90/MasterLok FS.  Consequently, it’s a favorite choice for architects and designers.

2ML90/MasterLok FS: With a 24” panel cover width and an option to snap or mechanically seam, our ML90 and MasterLok FS trapezoidal panels represent our most competitively priced standing seam panels that can span purlins up to 5’ OC.  ML90 and MasterLok FS system use are common in less visual, low slope applications.

Consequently, this product type has been a mainstay in the commercial/industrial and PEMB markets since the early 1960s.  Given its trapezoidal shape, it is better suited to straight panel runs and projects without valley conditions. Consequently, weathertightness warranties may not be available for all projects with this panel type.  


So which is the right product for your roof?  Only you can decide that, but it’s important to consider your appetite for ongoing maintenance vs. cost in your decision-making process.  If cost is your predominant criteria, then R-Panels may be your best option.  

If, however, you’re interested in a longer-term solution with a lower likelihood of leaks, then standing seam systems may be your best choice. If you’d like to discuss your specific project, contact us, we’re always here to help!

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About McElroy Metal

Since 1963, McElroy Metal has served the construction industry with quality products and excellent customer service. The family-owned components manufacturer is headquartered in Bossier City, La., and has 14 manufacturing facilities across the United States. Quality, service and performance have been the cornerstone of McElroy Metal’s business philosophy and have contributed to the success of the company through the years. As a preferred service provider, these values will continue to be at the forefront of McElroy Metal’s model along with a strong focus on the customer.

Topics: Standing Seam Systems, Commercial, R-Panel, Maxima

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