Types of Metal Roofs – Snap Lock vs Mechanical Lock vs Exposed Fastener

Types of Metal Roofs

Metal roofing systems continue to get more and more popular because they are rated to last 50+ years, look great, and are environmentally friendly. Metal roofing systems are built with metal panels cut to precise lengths to fit your roof’s profile. They are highly-rated roof materials for either commercial or residential buildings.

The primary types of metal roofs are:

  • Standing Seam – Snap Lock
  • Standing Seam – Mechanical Lock
  • Exposed Fastener

Each of these types of metal roofs have their own installation techniques. Which type of metal roof is best for your structure? Let’s explore…

Standing Seam Metal Roof – Snap Lock System

Snap lock metal roof systems consist of metal panels that have a male and a female seam that snap together. The panel is fastened to the roof deck with clips that connect to the panel underneath the rib. That means the screw is out of sight and not exposed to weather. Snap lock metal roofs are a great choice for roofs with a steeper pitch (3:12 or greater). This makes them a top choice for residential roofs. Many of the Evergreen, CO metal roofs and Golden, CO metal roofs built in recent years have snap-lock systems.

Advantages of snap lock metal roofs

Snap lock metal roof systems bring a simpler and quicker installation technique because the metal panels quickly snap together using mild pressure with a rubber mallet. This makes it a lower-cost metal roof option as compared to mechanical lock standing seam systems.

Disadvantages of snap lock metal roofs

Snap lock roofs are not recommended for low-slope metal roofs with a pitch under 3:12. Snow, ice, and water can accumulate more on low-slope roofs. This creates higher risk that water could infiltrate the seams. Snap-lock seams are designed to keep all water out, but with too much water accumulation they run the risk of leaks when installed on low-slope roofs.

Standing Seam Metal Roof Snap Lock
Snap Lock Metal Roof Profile

Standing Seam Metal Roof – Mechanical Lock System

Mechanical lock metal roof systems are similar to snap lock in that they both have a male and female seam to connect parallel panels. They are also both fastened to the roof deck with concealed fasteners underneath the panels. The key difference is while snap lock panels snap together, mechanical lock systems are locked together using either a mechanical or hand seaming tool. There are two type of mechanical seam locks:

  • Single lock – the panel seams are folded once at 90 degrees.
  • Double lock – the panel seams are folded once as noted above in single lock. But then they’re folded down again to create a full 180 degree seam lock. Nearly all mechanically seamed metal roofs in Denver are built using the double-lock process.

Advantages of mechanical seam metal roofs

Mechanically seamed roof systems are known to be more watertight than snap lock panels. With the seams being folded-over, water has a longer path to fight against gravity at the seam in order to get under the metal. This is why mechanical seam metal roofs are frequently found on commercial structures in the Denver area.

Disadvantages of mechanical seam metal roofs

Standing seam metal roofs build with mechanical seams require more manual time and effort during installation. That takes more labor, and results in higher overall cost. These systems are also more difficult to perform repairs on because of the need to “undo” the locked seam and get underneath the metal panels.

Metal Single Lock vs Double Lock
Mechanical Lock Metal Profiles

Exposed Fastener Metal Roof System

Exposed fastener metal roofs are different from standing seam systems in that the panels are fastened from the exterior. The fastener screws are visible from the outside. These screws have special washers designed to ensure no water seeps in through the fastener locations. Types of exposed fastener systems include Pro-Panel II, which are common on Colorado mountain cabin roofs, as well as Type-R panels, which are common on Denver industrial metal roofs.

Advantages of exposed fastener metal roofs

Exposed fastener metal roofs typically have wider panel coverage than standing seam, resulting in fewer panels needed to cover the same area. These roofs also are simpler to install as there is no seam-locking required other than fastening the panels using fastener screws. Both of these can result in a lower labor cost as compared to some standing seam roofs.

Disadvantages of exposed fastener metal roofs

Because exposed fastener metal roof systems are fastened with screws from outside the roof, a hole is created for the fastener screw. While the specialized fasteners do an excellent job of keeping water out (usually for decades), they do have higher risk of allowing water to seep in (especially under heavy snow or ice).

Pro Panel Roofing Denver
Exposed Fastener Panel Profile


What type of metal roof is right for your property? There are many benefits of choosing a metal roof, and the project managers at Sol Vista Roofing can help you determine the right system for you.