Standing seam comparisons: Snap lock vs mechanically seamed roofing

Mechanically seamed and snap-lock roofing share a number of similarities but their key differences make them best for different scenarios. This article will explore common standing seam systems, snap-lock vs mechanical. We will divulge their individual pros and cons, optimal scenarios for installation, and other factors to consider when making roofing decisions. 

Snap-lock vs. Mechanically seamed roofing: when is each type optimal?

Both snap-lock and mechanically seamed metal roofs are designed for commercial use. Snap-lock metal roofing is recommended in projects with short panel runs and slopes greater than or equal to 3:12. Snap-lock roofing should also be used in environments without extreme weather conditions. 

Meanwhile, mechanically seamed roofs can be used on low slopes (0 to 3:12) and on slopes above 3:12. When used on low-sloped roofs, it’s recommended to double-lock seams. Additionally, mechanically seamed roofs are optimal under harsh weather conditions and can be used on both longer and shorter length panels. Shorter length panels typically use a fixed clip. Which means exactly what it says: the clip is fastened at the fixed points and does not allow for thermal expansion and contraction. Contrast to this, the longer length panels require movement and as such require the use of the float clip version. 

Options beyond standing seam

An alternative to standing seam metal roofing is a through-fastened, otherwise referred to as "screw down" roof system. While this is the most economical option, it is not recommended for commercial applications due to it being the least-weather-tight.  We discuss this more thoroughly in our guide to exposed or concealed roofing fasteners.  

One of the main differences between standing seam and screw down roof systems is the lifespan. In fact, through-fastened (screw down) metal roof is not designed to last as long as standing seam roofs. A through-fastened roof's life span is about 20-30 years, while standing seam roofs can last 50+ years. It is important to note that this long life span is dependent on proper installation.

What should be considered when selecting a roof type?

Cost, installation time, roof slope, and weather conditions are key factors when comparing mechanical seam to snap lock roofs.

Which roof type is more affordable?

Snap-lock metal roofing tends to cost less as they don’t need a seamer to install. Meanwhile, mechanically seamed roofing costs more due to the extra time it takes to install and the required seaming equipment.

Which type of metal roofing is optimal for harsh weather conditions?

Mechanically seamed metal roofing is the most weather-resistant metal roofing option on the market. Snap-lock metal roofing is less weather tight when compared to mechanically seamed options but is a better option than a through-fastened roof.

How do the seam types compare when it comes to thermal movement?

Mechanical seam fasteners should only be used where there is minimal differential movement of the roof panels. Meanwhile, snap-lock roofs allow unlimited thermal movement.

Which roof type can be installed fastest?

Snap-lock metal roofing can be installed faster as it requires less tooling. Mechanically seamed roofs take longer to install as they require the use of a seamer. Double-lock mechanically seamed roofs will take even longer to install than their single-lock counterparts.