Standing Seam Metal Roofing Products

What is Standing Seam Metal Roofing?

Standing seam metal roofing panels are a product family of metal roofing. In the purest form, they are panels with male and female legs that are engaged and installed with clips to the roofing substructure. As panel options have grown however, it is common to see clipless panels included in this product family as well.

Regardless of the attachment method, it can consistently be maintained that standing seam panels do not use exposed fasteners in the plane of the panel during panel installation. Depending on project specifics, exposed fasteners may or may not be utilized for trim applications.

McElroy Metal offers five distinct standing seam systems that can be curved on the job site, lowering transportation costs and ensuring a proper fit.

138T & 238T Standing Seam System on Church

Standing Seam Metal Roofing Systems Overview

There are many nuances within the product family of standing seam. Click through the buttons below to learn more about the differences between panels and system types.

Product Families


These systems are typically for use on lower sloped roofs, often down to ¼:12. They are considered Hydrostatic, which means they can keep buildings water tight even when they are submerged under water for brief periods of time. Originally these types of products were designed for use over open framed purlins in pre-engineered building applications.  In recent years however, many designers  have begun using these types of products over plywood in a more architectural application.   


These systems are commonly used on slopes of 3:12 or greater. They are considered Hydrokinetic which means that they can keep buildings water tight while water is flowing over them as opposed to the Structural systems which can accomodate water submersion. Some panel styles in this family have load carrying capability, others do not. As the name implies, these types of products are used most commonly when the roof is intended to serve the dual purpose of enclosing the building envelope and serving as an aesthetic element of the building.

Engagement Method


Snapped panel systems consist of a male and female leg. Once the legs are properly engaged, pressure is applied and the panels snap together to complete the installation sequence.

Mechanically Seamed

This family of panels may also have a male and female leg that are “hooked” during installation; however, in T Style systems, the panels are connected only through the clip and a seam cap is applied over the connection. Once the job is complete a powered seaming machine is run along the entire length of the seam to make the system weather tight and complete the installation.

Attachment Method


Clipless standing systems are fastened through a pre-punched nailing flange. These flanges typically have repeating slots every 2-4” to facilitate attachment to the roofing deck, most often plywood.


Clipped systems consist of a clip that is integrated into the male/female panel legs and is then attached to the deck or purlins.

Panel Styles


These panels were the original standing seam panels in the industry.  As the name implies, when they are installed there is a trapezoidal opening at the eave and ridge.  The trapezoidal opening receives an inside closure and tape sealant to make the condition water tight. These panels are the most cost effective standing seam option; however, due to the trapezoidal area after installation, they aren’t widely used in architectural applications nor those with high visibility.  Instead, trapezoidal systems are best suited for simple buildings such as those without valleys.  They are often available in both snap and machine seamed versions and generally install from left to right.

Vertical Leg - Non Symmetrical

As the name implies, vertical leg panels have a vertical leg at the connection of the male/female leg, normally close to 90 degree. The systems typically install from left to right and often require the use of a seaming machine.

T Panel - Symmetrical Standing Seam

T style panels are one of the newer industry advancements. They combine the look and functionality of a vertical leg and have a batten cap that is then mechanically seamed in place. These panels allow for the easy removal and replacement of a panel in the field of the roof. This is a huge benefit that has been sorely needed in the industry. Consequently, they are quickly gaining favor as the preferred panel style.

Installation Approach


As the name implies, symmetrical panels look the same on both sides of the panel legs. While this might seem a minor difference, the impact is major. Symmetrical panels do not require left to right or right to left install. Instead installers can start at any (or multiple) points on the roof. Challenging areas can be skipped and returned to later. Symmetrical systems also allow for individual panel replaceability and in many cases allow for the original panels to be re-installed once the building modifications are completed. This feature is long overdue in the industry and carries obvious benefits to repair panels damaged by storms or to address issues common during building expansion or re-purpose.


The legs on the left and right of the panel are different for non-symmetrical panels. This requires that non-symmetrical panels always be installed in a progressive fashion, typically left to right. While not a huge differentiator during initial construction, should the roof ever require modification for new HVAC venting etc. or repairs, non-symmetrical systems can require that panels be removed from the roof back to the affected area. The original panels cannot be reinstalled so new panels must be purchased and installed to complete the remediation.

Curved Roofing

Curved Metal Panels

Curves are in! Design professionals appreciate curved metal roofing and the way curves transform the curb-appeal of structures. Curved metal roofing is popular as design accents or entire roofs. McElroy Metal offers five distinct standing seam systems that can be curved right on the job site, which lowers transportation cost and ensures a proper fit. McElroy's standing seam systems that can be curved are Maxima 1.5, Maxima ADV, 138T, 238T, and Medallion I.

Standing Seam Roofing Systems

Standing seam systems are used for a wide range of applications and projects. These systems feature interlocking seams that connect panels, giving the roof a distinct, and attractive, appearance. Furthermore, standing seam systems are manufactured from high-end steel or aluminum offering years of low-maintenance service life.

McElroy Metal standing seam systems are durable and weathertight, making them ideal for most any application.

Our standing seam systems include:

Medallion Architectural Standing Seam Roof Panel Rendering
  • 138T & 238T – These are symmetrical standing seam systems that are ideal for new or retrofit applications. McElroy Metal offers patented 138T and 238T recover systems that are designed to retrofit over existing metal or shingle roofs.
  • Instaloc – Offers a snap-together standing seam system that can be used with solid decking. It features a low-profile seam that makes Instaloc a wonderful choice for light commercial and residential applications.
  • MasterLok-90/MasterLok-FS – Trapezoidal systems designed for simple sloped roofs without dormers, hips or valleys.
  • Maxima – These vertical leg standing seam systems are available in a wide variety of options that enable customers to select a Maxima panel to match individual style and performance needs.
  • Medallion I/Medallion II – feature separate batten caps that are installed over adjoining roofing panels.
  • Medallion-Lok – Boasts a narrow, 1.75"-tall standing seam, giving the seam a clean, modern look and feel.
  • Meridian – Requires no clips and features a snap-together standing seam roof panel that is simple to install.
  • Mirage II – is a concealed fastener roofing panel that is commonly used in the mini-storage industry.

Discover the Benefits of Standing Seam Metal Roof Panels

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3D Cover 18 Ways To Reduce Risk Standing Seam Metal Roof Panels


Standing Seam Retrofit Systems

McElroy Metal is the industry leader when it comes to retrofit systems. McElroy’s retrofit offerings include flat-to-steep slope, Metal-over-Metal and Metal-over-Shingle solutions. We'll ensure you can find a cost-effective and viable metal retrofit system to fit individual needs.

Our retrofit system offerings include:

  • 138T Shingle Recover – Can be installed directly over existing shingles and delivers energy-saving Above Sheathing Ventilation (ASV), making the system a terrific choice for both commercial and residential projects.
  • 238T Metal-Over-Metal Recover – As the name implies, the existing roof panels remain in place for metal over metal recover systems.  Skipping the tear off step not only saves building owners time and money but perhaps more importantly, their daily business operations aren't impacted.  These systems feature a symmetrical 238T standing seam panel and are proven to last two to four times longer than single-ply recover.
  • Low Slope to Steep Slope – We offer retrofit assemblies that are easy to erect and are a great way to convert worn out flat roofs into functional and highly attractive steep slope roofs.
Standing Seam Retrofit Systems

Our retrofit systems offer customers and building owners viable and cost effective solutions for worn out existing roofs. McElroy Metal’s experience technical staff is available to help customize retrofit solutions, so give us a call. We are always happy to help develop creative and functional solutions with metal!

Advantages of Standing Seam Metal Roofing


Concealed Fasteners

Concealed fasteners are one of the biggest advantages of standing seam roofing systems. In exposed fastener systems, the washer around the screw is made of neoprene material. Over time, sun can degrade the washer material and cause shrinking or cracking. When this phenomenon occurs, water can penetrate the building around the fastener/washer. The only correction for this is to back out all the screws and insert new oversized screws. Since there are no exposed screws with standing seam panel systems, they are considered a much more weather tight system.


Expansion/Contraction through Clip or Slotted Flange System

Standing seam systems allow for expansion/contraction through either a clip or slotted flange system. Steel expands in heat and contracts in cool temperatures and will literally move on the roof. Exposed fastener systems, while less expensive to install, do not allow for expansion and contraction. In longer panel runs, the screws can wallow out on exposed fastener systems and allow water to penetrate the building around the fastener. The clip in standing seam systems allows the panel to float from eave to ridge to accommodate the phenomena of expansion and contraction. Check this out to learn more.


On-Site Panel Production For Long Lengths

While not available with every manufacturer, some of the major manufacturers (McElroy Metal included) have the ability to produce some standing seam panels on-site in lengths up to 250’. Single piece panels are quicker to install because the lap details required to join multiple shorter length panels are generally very time consuming for installation crews. In addition lapped systems often require additional parts and pieces which can further drive up the cost over continuous jobsite produced panels. Lastly, the weakest link in any roofing system is a lap so when one can be avoided it’s generally preferred.



Aesthetics. Standing seam panels typically offer a taller and distinct vertical leg and fewer (if any) minor ribs in the center of the panel. This tall vertical leg can offer a nice shadow effect and the illusion of a flat pan in between the major ribs which many architects and building owners prefer.


Extensive Testing

In order to meet demands of the architectural community, building codes and life safety issues, standing seam panels are subjected to more testing than exposed fastened type systems. Common tests include those for uplift, air and water, impact and fire resistance.


Availability of Weather Tightness Warranties

While certainly not required, some building owners want assurance that their building will be leak free for perhaps up to 20 years. While there are additional charges and criteria to be met, standing seam systems can often offer Weather Tightness Warranties where exposed fastener panel systems cannot.