When it comes to standing seam metal roofing, the most weather-tight and durable option is the mechanically seamed panel. If you’re considering a metal roof for your next residential or commercial project, this comprehensive guide will walk you through everything you need to know about 2″ mechanically seamed standing seam roofing. From cost and performance to available options and installation tips — we’ve got you covered.
Overview of the SMI 2.0″ Mechanical Seam Profile
The SMI 2.0″ Mechanical Seam is a standing seam mechanical lock system. This means it is installed using hidden clips and fasteners on the male leg of the panel, while the female leg is seamed to lock it into place. When the panel is formed using steel, the maximum width is 18 inches. For aluminum, the maximum width is 16 inches. This profile supports materials ranging from 22 gauge to 24 gauge steel or 0.40 aluminum. Even if you opt for a heavier gauge material or narrower panel width, the engineering for this panel still holds valid. To form the panel, approximately 5 and 13/16 inches of material is used.
Applications in Steep and Low Slope Roofs
Mechanical seam profiles like this one are suitable for both steep slope and low slope applications. These are considered hydrostatic systems, which means they are designed to hold water and stay weathertight while the water drains slowly off the building. The SMI 2.0″ Mechanical Seam can be installed at slopes as low as ½:12 for steel and 2:12 for aluminum. If the panel is being installed below a 2:12 slope for steel, it must include sealants that meet ASTM E 2140 standards.
Structural Strength and Open Framing Support
One important distinction of this profile is that it is a structural panel. That means it can be used over purlins in open framing applications. Later in this post, we’ll look at specific engineering requirements for these types of installations. Engineering is a key aspect of this profile because it provides real-world data gathered through rigorous testing. When the panel is installed according to the engineering specifications, it ensures optimal performance and durability.
Engineering and Testing Standards
The SMI 2.0″ Mechanical Lock profile includes a UL 90 construction number. In addition, Sheffield Metals has performed several lab-based engineering tests for both steel and aluminum panel variants. These tests were conducted over various substrates, including plywood, B-Deck, and B-Deck with ISO. The panel has undergone UL 580 and UL 1897 uplift testing, ASTM E 1680 air infiltration testing, ASTM E 1646 water penetration testing, and ASTM E 2140 water submersion testing for steel over plywood. It also has a Class 4 impact resistance rating via UL 2218 and can be used in Class A fire-rated assemblies according to UL 790 testing.
Introduction to Mechanically Seamed Metal Panels
This article is part of the Metal Roofing Learning Channel, brought to you by Western States Metal Roofing — your source for high-quality panels available in a wide range of colors and finishes, all at factory-direct prices.
MS2 (Mechanically Seamed Panels) are among the most weather-tight and long-lasting standing seam roofing panels available. These concealed fastener panels are designed with a male and female leg that align using clips and are locked together using either a mechanical or hand seamer. The unique fastening method used with MS2 panels gives them superior leak resistance and an exceptionally secure fit.
Open Framing and Load Testing
For open framing applications, the panel has passed ASTM E 1592 uplift testing and Factory Mutual 4471 foot traffic testing. FM 4471 states that this panel can handle a 250-pound concentrated load. If your project is located in Florida or Texas, you’ll be glad to know that the panel holds both Florida Building Code (FBC) and Texas Department of Insurance (TDI) approvals. These approvals apply when the panel is used over plywood, B-Deck, B-Deck with ISO, and in some cases, even open framing.
Warranties and Future Testing Plans
This panel is eligible for weathertight warranty projects through Sheffield Metals. It also qualifies for the standard SMI 40-year PVDF paint warranty as well as Galvalume® warranties. Sheffield Metals is continually working to expand its engineering capabilities. Upcoming plans include finishing High Velocity Hurricane Zone (HVHZ) approvals for Florida, upgrading non-engineered profiles with additional testing, and enhancing current engineered profiles with even more data. Stay tuned for updates on these developments.
Ideal Use Cases for the SMI 2.0″ Mechanical Seam
The SMI 2.0″ Mechanical Seam panel is an excellent option for both steep and low slope roofing projects. It is most commonly used in commercial applications, especially when installed over open framing. The panel carries a UL 90 rating with purlin spacing up to four feet. It’s also a solid choice if you need an engineered system, want to benefit from a commercial weathertight warranty, or have a structure that requires a hydrostatic roof condition.
When This Panel May Not Be the Best Fit
This panel may not be the right choice if your roof has enough slope to accommodate a snap-lock profile. Snap-lock panels are easier and quicker to install because they don’t require the additional labor associated with seaming. Also, the two-inch rib on the mechanical seam panel is quite large, which might not be visually suitable for all designs. This profile is not recommended for DIY projects either, due to the technical requirements involved in its installation.
Installation Process Over Solid Decking
When installing this panel over solid decking, always follow the engineering guidelines. These include approved deck substrates, correct clip spacing, approved accessories, and other required details. For this demonstration, the panels were pre-fabricated with a one-inch bend at the eave and a one-inch box at the top. If you’re interested in fabricating these panels yourself, links to helpful tutorials are available in the video description.
The panel hooks onto the eave and is pinned at the top with a couple of fasteners. Then, engineered clips appropriate to the material and substrate are attached to the male leg. The specific engineering requirements for your project will determine which type of clip you should use. A bead of sealant is applied at the end of the panel to prevent water siphoning. Afterward, the next panel is installed by hooking onto the eave, placing the female leg over the male leg, and seaming the two together
Seaming the Panels: Manual vs Robotic
There are two types of seams: a 90-degree seam and a 180-degree seam. Most of the time, engineering specifications require a 180-degree seam. Typically, seaming is done using a robotic seamer, which ensures a clean and consistent result. In this demonstration, a hand seamer is used to show the process, but it is labor-intensive and not practical for full-scale roofing jobs unless you’re working in tight or hard-to-reach spaces.
Hand seamers are useful for applying a 90-degree bend over clip locations. This creates a fixed point while laying panels, allowing you to return later with a robotic seamer to complete the 180-degree seam. Adding a 90-degree seam first makes it easier for the robotic seamer to finish the job. In this example, the panel is finished using a 180-degree hand seamer, though this is not the standard approach. Robotic seamers provide a more consistent finish and are much easier on the installer.
Thermal Expansion and Movement
Because the panel is only pinned at the top and uses butterfly clips that move freely, it can expand and contract as needed at the eave. Sheffield Metals provides an installation guide with a Thermal Movement Chart. This chart shows how much space to leave at the eave based on the metal used, the deck material, and the panel length. It’s important to follow these specifications to prevent damage due to thermal expansion and contraction.
Installation Over Open Framing
When installing over open framing, a different set of clips is used. These clips are designed to float the panel off the purlins by approximately half an inch, which helps reduce purlin chatter. Installation details for this profile, both for commercial and residential projects, can be found at sheffieldmetals.com. These details are highly recommended for ensuring a high-quality and long-lasting installation.
Why Choose Mechanically Seamed Panels?
The way MS2 panels lock together makes them ideal for areas with harsh weather, including snow, heavy rainfall, and extreme wind. Their exceptional weather-tightness makes them a preferred option for low-sloped roofs and demanding climate conditions. They are suitable for both residential and commercial applications, offering not only high performance but also modern style.
When installed correctly, MS2 panels have a projected lifespan of 40 to 60+ years. In other words, they are considered a lifetime roof — built to last for decades with minimal maintenance.
What This Guide Covers
This buyer’s guide will give you insights into several important aspects of mechanically seamed panels, including:
- Cost breakdown
- Available panel options
- Locking system types
- Advantages and drawbacks
- Ideal use cases
By the end of this guide, you’ll be able to determine whether mechanically seamed panels are the right choice for your project.
Cost of Mechanically Seamed Metal Roofing
There are several components that influence the total cost of a mechanically seamed roof system. On average, mechanically seamed panels cost between $2.50 and $5.00 per square foot. However, that’s not the complete picture. Additional elements like accessories, trim, and underlayment will add to the total expense.
Each roofing project is unique and will require different quantities and types of trim. Western States Metal Roofing can provide an estimate once a materials list has been generated by you or your contractor.
It’s important to note that Western States Metal Roofing does not offer installation services. However, if you need help finding a qualified installer in your area, you can email them with your project details to receive a referral.
Available Panel Options and Specifications
Mechanically seamed panels are available in a 2-inch seam height. The standard gauge thickness is 24 gauge, although 22 gauge is available for custom orders.
Panel widths are typically offered in 12-inch, 16-inch, and 18-inch options, but can be custom-made from 12 inches to 24 inches. The maximum factory-made panel length is 52 feet, due to shipping limitations. For panels longer than 52 feet, on-site roll forming is available for contractors in Arizona working on projects with over 5,000 square feet of material.
Benefits of Mechanically Seamed Roofing Panels
Mechanically seamed panels come with all the general benefits of metal roofing but also bring additional unique advantages.
Superior Weather Tightness
One of the most significant advantages is their double-lock system, which makes them the most secure and weather-tight standing seam panel on the market. This feature is particularly important in snow-prone regions, where roofs are exposed to heavy and prolonged snowfall.
Higher Quality Performance
Mechanically seamed panels create an extra-tight fit that drastically reduces the chances of seam failure. They are strong enough to remain in place under extreme conditions and are suitable for roofs with a pitch of 1:12 or greater.
Locking System Types: Single vs. Double Lock
Mechanically seamed roofing panels can be installed using two types of locking systems:
Single Lock System
In a single lock system, the seams are folded once at a 90-degree angle. This method is easier to install and typically used in milder climates where extreme weather tightness is not as critical. However, this method is less common and not recommended for areas with heavy rain or snow.
Double Lock System
The double lock system is the standard for mechanically seamed panels. In this method, the seams are folded twice at a 180-degree angle, creating an extremely tight seal. Though it requires more labor and comes with higher installation costs, the double lock system provides maximum weather resistance and long-term durability. It’s the better choice for locations that experience frequent storms, heavy rainfall, or snow accumulation.
Drawbacks to Consider
Despite its strengths, mechanically seamed roofing also has some drawbacks.
Labor-Intensive Installation
One of the primary concerns is the labor intensity. Before actual seaming begins, every clip on each panel must be prepared and seamed by hand. This process increases both labor time and installation costs compared to simpler standing seam systems.
Not Ideal for Everyone
Mechanically seamed panels may not be the right choice if:
- You’re on a tight budget
- You want a simpler installation
- You live in a mild climate
- Your roof has a steep pitch (greater than 3:12), where extra weather tightness isn’t necessary
Aesthetic Options and Color Variety
Mechanically seamed panels are available in a premium Kynar® paint system, which is known for long-lasting color retention and protection. You can choose from over 100 colors, including:
- Standard Kynar colors
- Matte finishes
- Gray zinc tones
- Rusted finishes
- Copper-inspired shades
This wide variety allows you to match your roofing to virtually any exterior design preference.
Is Mechanically Seamed Roofing Right for You?
To summarize everything we’ve covered: a mechanically seamed roof is a great fit for your project if:
- You live in snow country or a region with extreme weather
- You need a roof that’s extra weather-tight and secure
- Your roof slope is less than 3:12, where extra protection is essential
Request a Free Quote or Color Chip
Interested in moving forward with mechanically seamed roofing? You can request a free quote or color sample by filling out the request form on the page.
And if you’re still curious about standing seam roofing systems, check out our other educational videos released weekly. Be sure to check our offcial website Standseamroofing