Mechanically Seamed vs Snap Lock Metal Roofing

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Jun 14, 2022

Mechanically Seamed vs Snap Lock Metal Roofing

Standing seam metal roofs are becoming increasingly popular due to their stylish appearance, durability, and longevity. Standing seam metal roofing systems are a premium roofing solution, but there are a number of products and installation methods available that can affect your roof’s performance and price.

Two of the most common styles used in both residential and commercial standing seam metal roofing systems are mechanically seamed and snap lock. Differences in appearance after a standing seam metal roof’s installation are nearly undetectable so it’s important to understand the functional differences between these types of standing seam roofing systems so that you know which profile is the best fit for your next metal roofing project.

What is a Mechanically Seamed Roofing System?

In a mechanically seamed roofing system, the metal panels have vertical legs that line up with each other. During the installation process, these vertical legs are seamed together with a hand seamer or an electric seamer. The mechanically seamed panels are connected to the roof substrate using a concealed clip system. There are two types of mechanical seams that are used in standing seam metal roofing systems: single lock or double lock.

Mechanically seamed panels are especially great for low-slope roofs where there is a chance of heavy rain runoff, pooling water, or snow buildup. This is because the panel’s tightly sealed seams close any space where water has the potential to collect and lowers the inherent risk of water leaking between the seams.

Single Lock vs Double Lock

Both single lock and double lock seams create a very weather tight seal for a metal roofing system. Determining which type of seam will perform best for your roof application depends on several factors including environment and the slope of your roof. Commercial roofing systems tend to be low to no slope and can definitely benefit from mechanically seamed metal roofing systems. An added benefit is that years down the road, a roof coating can be applied to a well maintained commercial metal roof, extending its functional life for many years.

In a single lock mechanically seamed roofing system, there’s only one fold of the seam. This 90 degree seam performs well in more mild environments. Since a single lock system is only folded once, it can take less labor to install and can be easier to repair than a double lock system.

In a double lock mechanically seamed roofing system, seams are folded twice, or 180 degrees. The additional lock keeps the panels from coming undone. Double lock panels are best for low slope metal roofing applications that need to be extra weathertight. Double lock seams perform well and are much stronger in the face of wind uplift, foot traffic, rainwater runoff, and even snow buildup.

Why Choose a Mechanically Seamed Metal Roof

Low slope roofs have the potential for pooling water. This is problematic for any roofing system. Mechanical lock panels can be used on low slope roofs because the panels are seamed together, allowing for a more watertight seal. The seaming tool used during the metal roof’s installation keeps the seam closed tightly. This reduces the chance of moisture penetrating the roof structure. To further waterproof the roof, a sealant can be added to the panel’s legs.

Because single and double lock standing seam profiles are seamed mechanically in the field, their seam heights can vary. Higher seams have the potential to make the roofing system’s structure more stable, but a lot of people prefer to have a thinner, narrower seam to create a low profile look. Metal roofing panels that have been mechanically seamed together have a more rigid structure, making them even stronger. Expansion clips can be used in order to account for regular expansion and contraction and make it so the roof can tolerate greater temperature changes.

Mechanically seamed roofs can be more labor intensive and take more time to install than other types of metal roofing systems due to the use of hand crimpers or electric seamers. An important consideration when deciding between single lock and double lock seams is that double lock seams can be more difficult to repair if they are damaged. The extra secure fit that a double seamed panel provides is exactly what makes repairs more time consuming. Mechanically seamed panels need to be unseamed for repairs.

What is Snap Lock?

Another common type of standing seam metal roofing panels are snap lock panels. Snap lock panels are roll formed into shape and have a male and female leg that snap together. The roofing system employs a hidden fastener system where clips are used to attach the panels to the roof deck. The clips fasten on the underside of the panel and out of view to preserve the sleek look of the metal roof.

Why Choose a Snap Lock Standing Seam Metal Roof?

A snap lock standing seam metal roofing system consists of panels that snap together, no mechanical seams necessary. This makes the installation process faster. Also, less labor and tools are needed than a mechanically seamed metal roofing system, which has the potential to reduce the cost of your metal roof’s installation.

Standing seam metal roofs are known for being very weathertight and are widely used. This is because the hidden fasteners do not penetrate the metal panels so there’s less chance for water penetration than with an exposed fastener system. Exposed fasteners penetrate the metal panels to adhere to the roof deck. Every point of penetration in an exposed fastener metal roofing system is a possible point of moisture intrusion.

Although snap lock metal roofing systems are more weathertight than some other types of metal roofs, mechanical seams do provide the most weathertight metal roofing options. Snap lock metal roofs are great for most roofs with a 3:12 pitch and greater but are not the right choice for a very low sloped roof that is less than a 3:12 pitch due to the possibility of pooling water. Snap Lock standing seam roofing is commonly used for both commercial and residential buildings.

Since the metal panels snap together and no seaming is required for a snap lock metal roof, roof repair or replacement is easier. Rather than having to unseam each panel, damaged panels can be unsnapped, and the new panels snapped together. This work is best performed by a metal roofing company, but it is much less time consuming than repairing a mechanically seamed roof.

There are some important things to consider when choosing a snap lock profile. If you live in an area that experiences extended cold weather, the buildup of snow or ice that freezes and thaws over time can potentially disengage the panel seam. This is not a common occurrence but something to be aware of. Also, areas that experience extreme weather and high winds are better suited to mechanically seamed metal roofs.

The slope of the roof is another consideration when choosing a snap lock roof. We mentioned earlier that snap lock panels perform best for roofs that have a 3:12 pitch and greater. This slope is known as a hydro-kinetic roof application. This is because snap lock panels are designed to shed water, not hold water. Sealant can be added to snap lock panel seams to improve waterproofing capabilities, but even with sealant these panels should not be used for low slope applications.

Hiring a Local Metal Roofing Company

It’s important when choosing roofing company to install your metal roof, that you choose an experienced, local metal roofing company that specializes in metal roofing. A metal roof installation varies greatly from a shingle roof installation. A metal roofing company will be familiar with and prepared for the potential issues that can arise during a metal roof installation.

When it comes to installing mechanically seamed metal roofing systems, seaming devices take experience and mechanical knowledge to use properly and not damage the seam during the installation process.

Although the term snap lock makes it sound like a snap lock metal roof installation is easy, it takes training and experience to install properly. Snap lock panels need to be tightly snapped to engage the panel seams for the most effective weather resistance and so that they don’t disengage over time.

Another reason to hire a local metal roofing company is that each metal roof needs to be specifically designed and customized for the building where it is being installed. A lot of industry experience, installation experience, training, and product knowledge goes into choosing the right installation design and method based on a building’s location, roof pitch, use, environment, timeline, and budget.

A metal roofing company will be more experienced in metal roofing and have more product knowledge as well. Not all metal panels are manufactured the same way. It’s important that your roofing company understands all aspects of the materials they are using as well as the advantages of some materials over others. They need to know the different characteristics of each profile type and how they perform in different conditions over time so that you can make the right choices for your metal roof.

Even after you choose your panel profile, there are many other more detailed decisions to be made. For example, some choices that need to be made are leg panel height as taller leg panel heights can add to the metal panel’s strength and water resistance, whether you should use expansion clips in your metal roof application, which paint system will perform best in your region, and many more.

At Gravity Metal Roofing, we specialize in metal roofing. We give every project the time and consideration it deserves and we strive to help every client make the best choices for their style and budget. We have the best installers in the industry, customize every project for our client’s needs, and warranty our work so you can rest assured that your roof will protect your home for many years.

Final Thoughts

Both mechanically seamed and snap lock profiles are excellent options for standing seam metal roofing. The profile that you choose really depends on your expectations for your metal roof. At Gravity Metal Roofing, we’ll meet with you to discuss your priorities for your metal roof’s performance and take all the factors that will affect the longevity of your metal roof into consideration to help you make the best choices for your home or business.

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