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Mechanical Lock vs. Snap-lock Metal Roof Profiles: Which Is Better?

Snap-lock and mechanical lock profiles are great options for standing seam metal roofs. However, there are certain features, advantages, and disadvantages to using each profile you should know before you make a choice.

Katie BowlesOctober 28, 2020

Mechanical lock and snap-lock profiles are the two most common styles used in standing seam metal roof systems for residential and commercial building applications. If you’re considering using one of these styles of metal roof profiles, do you know the differences between them? When should you use a mechanical lock profile as opposed to a snap-lock profile and vice versa?

At New Tech Machinery (NTM), we manufacture various portable roof panel machines designed to produce standing seam panel profiles. We also understand the importance of researching what makes each of these profiles unique and when to utilize each profile style can make your decisions and projects easier.

Understanding the characteristics, advantages, and disadvantages of these types of panel profiles can help you decide what profile is the best option to use on your next metal roofing project.

In this article, we’ll cover:

  • The characteristics of mechanical lock profiles and snap-lock profiles
  • Advantages and disadvantages of using mechanical lock and snap-lock profiles
  • What to consider to help you figure out which profile to use on your project
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What Is a Mechanical Lock Profile?

Mechanically seamed roofing systems have vertical legs that line up with each other and are seamed together with a hand or electric seamer. Using an electric seaming tool can allow for a tighter and more consistent seam than just hand forming them. The concealed clips are then a part of the mechanical lock system.

Mechanically seamed panels utilize clips to connect the panels to the substrate. For low-slope roofs, especially where there’s a chance of a heavy build-up of snow or rain runoff, mechanically seamed panels are the best choice since the two panel’s seam closes any space water may collect and lowers the risk of leaking between seams.

Two types of mechanical seams used on standing seam metal roofs are single lock or double lock.

A single lock seam refers to the fact that there’s only one fold of the seam. It’s a 90-degree seam, and although this style won’t perform as well as a double lock profile, it does well in mild environments. You will need to check with the manufacturer to ensure the roof system’s engineering will allow for the use of a single lock profile. Some of the benefits of using a single lock profile are that they take less labor to install and are easier to replace should damage occur than the double lock alternative.

Double lock seams are those that have been folded over twice (or 180 degrees). They are best for low-slope building applications that may need to be extra weathertight. Double lock seams are much stronger for wind uplift and foot traffic and hold up better in extremely cold-weather regions. One consideration to make when using this type of panel is that they are more labor-intensive to install and replace.

(article) Mechanical Lock vs. Snap-lock Metal Roof Profiles: Which Is Better?

Advantages of Using Mechanical Lock Profiles

Can be used for lower slope roofs – One advantage of using mechanical lock panel profiles is that you can use them on low slope buildings (those of 2/12 pitch and less) unless otherwise dictated by the project specifications or panel design limitations. Usually, a seam sealant will be required when going below a 2/12 pitch. Please check with the manufacturer for the minimum pitch they recommend.

Varying seam heights – Since this type of standing seam profile is seamed mechanically in the field, they can have varying seam heights. Higher seams may add more stability to the roofing system’s structure. However, if you don’t want your seam to be “bulky”, they can have a thinner seam that is narrow and low-profile.Better watertight capabilities – On low slope roofs, especially, the potential for water remaining on the roof can be problematic. In this instance, using a mechanical lock profile would be best since the way that these panels are seamed together allows for more watertight and waterproofing capabilities.

Using a seaming tool for installing mechanical lock profiles keeps the seam tightly closed, and thus closes the spaces where water might collect and reduces the chance of leaking into the roof structure. A sealant can also be added to the panels’ legs to further assist in waterproofing the roof.

Durable and strong profile – The way these panels are mechanically seamed together adds rigidity to the structure and makes them even stronger against high winds and hazardous weather. In this instance, expansion clips may be used to tolerate greater temperature changes when the standing seam metal roof system contracts or expands.

Disadvantages of Using Mechanical Lock Profiles

More labor-intensive and costly – Due to the hand crimper or electric seamer needed to connect the mechanical lock panels, this style can be more labor-intensive to install and more expensive. While some companies might want to purchase their own seamer, you can also look into renting one, saving you from a large upfront investment. When renting a mechanical roof seaming device, you also don’t have to worry about keeping the machine serviced or in proper working order.

More difficult to repair – One of the best things about a standing seam metal roof system is the minimal maintenance it takes to keep it in good shape. However, some profiles are more difficult to repair should they become damaged. Mechanical lock profiles, especially those with double lock seams, need to be unseamed, a more time-consuming and challenging process.

Potential problems while seaming or unseaming panels – Problems can happen at any time. One possible issue with using a seaming device is that the seamer may jump and damage the seam. If the seaming device is misused or out of adjustment, it can cause costly damage to the seam or metal panel. It’s all preference on whether installers like to use hand seamers or electric, but knowing how to use the tool properly is the first step to avoiding potential problems. 

Another potential issue is the “telegraphing” of the clips through the panel seams, showing where each clip is placed within the panel structure. Should you ever need to unseam a panel, there’s also the potential risk of cracking the material when unseaming the panel legs or while seaming them back together.

Metal Roofing Rollforming Glossary

What Is a Snap-lock Profile?

(article) Mechanical Lock vs. Snap-lock Metal Roof Profiles: Which Is Better?

Snap-lock panel profiles are another very common type of standing seam panel profile. They are also rollformed into shape, either using an in-plant or portable rollformer, with a male and female leg which snap together. Unlike mechanical lock profiles, this type doesn’t utilize a seaming tool to connect the panel legs. 

This profile is typically used on a roof slope of 3:12 and greater unless otherwise specified by the manufacturer. Snap-lock profiles are widely used on both commercial and residential buildings.

As is stated in the Metal Construction Association’s (MCA) Metal Roof Installation Manual, snap-lock profiles use fasteners or clips to attach the metal panel to the roof deck, but the seams are snapped into place. However, it is crucial that the whole panel seam is securely snapped into place and fully engaged.

Advantages of Using Snap-lock Profiles

No seaming tools necessary – This profile style has a male and female leg that just gets snapped together, so you don’t need any seaming tools to connect the panels. This method of installation saves you time and money. 

Easier and faster to install – Since snap-lock profiles don’t require any mechanical seaming, this system typically requires less labor to install and is generally cheaper. Not only are these profiles easier to install, but should you need to replace or repair them for any reason, you unsnap the panels and snap the fixed or new panels back together. It’s not as easy as it sounds, but it’s easier than replacing a mechanically-seamed panel. 

Disadvantages of Using Snap-lock Profiles

Design considerations for cold areas – For buildings in regions with cold weather, snap-lock profiles could be a concern depending on the building design and snap-lock panel style you choose. Build up of snow or ice freezing and thawing over time can expand the ice, potentially disengaging the panel seam. While this is not a common occurrence, it is something to consider as not all snap-lock panels perform the same.

Must be securely snapped into place – Again, according to the MCA Metal Roof Installation Guide, it’s critical that you tightly snap and engage the panel seams for the most effective weather resistance and so that they don’t disengage over time.

Restricted to steep slope (hydro-kinetic) roof applications – Snap-lock profiles are mainly used only on steep slope architectural building applications, those of 3/12 roof pitch and greater. The reason for restricting their use on steep slopes is because these style panels are designed to shed water, not hold water. Again, you can add sealant into the legs of the snap-lock panels to assist in waterproofing the panel legs.

Considerations to Make When Deciding to Use Mechanical Lock vs. Snap-lock Profiles

Does the roof have a steep slope or low slope?

If you know whether the roof is a steep or low slope, that will help you decide which profile to use. 

As we said before, mechanical lock profiles work best on low slopes since they are more water-resistant and less likely to leak between the seams. Use snap-lock profiles as a more cost-effective option on steep slopes where there’s less likely to be water ponding on the roof. Taller panel leg heights can also contribute to panel strength and the ability to resist water.

How difficult would it be to perform maintenance or repairs on the panel?

Chances are, during the lifetime of the standing seam metal roof, repairs or some form of maintenance will need to happen. Just as you would perform regular maintenance to take care of your car, you’ll also need to maintain your standing seam metal roof system, and the kind of profile you use may make this process more difficult. Mechanical lock profiles need to be unseamed before you can make any repairs or replace the panel —a more complicated process than un-snapping the panels as you would with a snap-lock profile.

(article) Mechanical Lock vs. Snap-lock Metal Roof Profiles: Which Is Better?

How labor-intensive and costly is the installation? 

You should also consider how labor-intensive the process will be to install the panels onto the roof system and how much time it will take. The panel installation process for snap-lock profiles is relatively straightforward: attach the metal panel to the roof deck using fasteners or clips, and snap the panel seams together. However, with mechanical lock profiles, it requires a hand or electric seamer to bend the panel legs over each other. Not only is this process more time-consuming, but it is generally more expensive.

What is the weather and temperature like in the area?

Lastly, you need to think about what the weather is typically like in the region you’ll be working on the metal roof system. If the area gets a lot of harsh weather, high winds, cold and freezing temperatures, utilizing a mechanical lock profile is your best bet. 

Final Thoughts

Both mechanical lock and snap-lock profiles are great options for standing seam metal roofing, but there are certain factors to consider when deciding which one to use. 

After understanding the different characteristics of each profile type, advantages, and disadvantages, you’ll be better able to make the right decision for your metal roof. Also, refer to the manufacturer for their recommendations as panels aren’t all made the same way.

With 29 years of manufacturing portable roofing rollformers and equipment, New Tech Machinery knows how important it is to be an educated customer. We strive to provide our customers with the educational and informative resources that can help them feel more confident in their metal roofing decisions. 

If you have additional questions regarding standing seam panel profiles, portable roof panel machines, and equipment, feel free to contact us. And be sure to check out our learning center for more in-depth articles, videos, and downloadable resources.

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