Roofing fasteners: exposed or concealed

Metal roofing is typically installed in either a standing seam or exposed fastener configuration. Although both systems provide the advantages of a metal roof, each respective system has distinct pros and cons

Exposed fastener versus standing seam roofing

As the name implies, exposed fastener systems will feature fasteners exposed to the external environment after installation. The heads will be clearly visible to viewers of the completed building. However, these are often painted to match the color of the roofing panels. SFS has a color-matching tool that helps customers ensure their exposed fasteners blend in perfectly with whichever panel they use.

In contrast, standing seam roof systems have no exposed fasteners after installation. Instead, metal clips are utilized to attach the roofing panels to the deck. No products are installed into the physical panels, and this results in a less intrusive appearance.

Pros and cons of exposed fastener systems

Advantages	Disadvantages
Least expensive option Minimal labor required Easy installation Less difficult to repair Fasteners can be applied universally	Prone to leaks Subject to damage from panel movement Larger risk of corrosion damage from rusting fasteners Less favorable appearance More required maintenance Cannot be installed on a roof with lower than 3:12 pitch Performance issues on longer panel runs

Pros and cons of standing seam systems

Advantages	Disadvantages
Low risk of corrosive damage Less intrusive appearance Limited risk of leaks if properly installed Typically allows for more panel movement before failure Less Required Maintenance Suitable for low sloped applications below 3:12 Better suited for longer panel runs	Most expensive option Labor intensive Clips are panel specific and cannot be utilized with different profiles More difficult to repair

Cost and labor: standing seam versus exposed fastener

Exposed fastener systems will almost always be a less expensive option when compared to standing seam systems. This is due to both the reduced material costs and simplified labor requirements.

Exposed systems only require metal panel and fastener components for installation into the roof-deck. However, standing seam systems require metal panels, panel specific clips, and appropriate clip screws. This results in additional material costs and complexity.

Standing seam systems are installed by clamping metal panels to the roof deck with specialized clips. Installers will need to lay out the panels, attach clips to the panels, install the clips into the deck, and, for some systems, seam the metal panels together. In contrast, exposed systems only require the installation of the metal panels directly to the deck. This results in a large reduction in labor complexity for exposed systems. Installers will require less training, and installation will typically require less time for these systems.

Appearance: standing seam versus exposed fastener

One of the major downsides to exposed fastener systems is the appearance of fastener heads on the roofing panel. There have been many improvements in both color matching technology and low profile head design to ensure the least obtrusive appearance for these systems. However, most observers agree that standing seam systems, which feature no external fasteners, provide a smoother and more appealing profile.

Corrosion performance: standing seam versus exposed fastener

Due to the lack of external parts on standing seam systems, there is a lower probability of corrosive damage occurring. However, exposed fasteners are susceptible to external environmental conditions. If these fasteners have a lower corrosion rating than the metal panels used, rust will begin to appear earlier. Additionally, due to potential differences in fastener material and panel material, some systems may be damaged by galvanic corrosion, which occurs when two separate metals are in contact and moisture is applied. In contrast, standing seam systems will not be susceptible to these types of issues.

Applications: standing seam versus exposed fastener

Certain applications are better suited for each respective roofing system.

Exposed systems have a number of limitations that will restrict usage on some jobs. For instance, due to thermal movement, exposed systems typically should not be used for long panel runs. This is because changes in roof temperature will cause slotting in the panels. This type of damage increases the size of holes created during fastener installation and may lead to leaks and structural damage. In addition, damage may occur when used on low slope roof pitches (smaller than 3:12).

In contrast, some standing seam systems are rated lower than exposed systems for wind uplift. This is a value utilized to determine the wind pressure that a roof can sustain before permanent deformation occurs. A designer should ensure the uplift rating of the system used is acceptable for the required application.

Maintenance: standing seam versus exposed fastener

Standing seam systems typically require less maintenance than exposed fastener systems but are much more difficult to repair.

Maintenance on exposed systems typically consists of replacing damaged fasteners. The damaged fastener is removed and replaced with a larger diameter fastener. As a result, the metal panels are usually still acceptable after failure of exposed fasteners. In contrast, failures on standing seam systems are exceptionally difficult to repair and may require extensive replacement of panels, clips, and fasteners. This requires additional labor and materials.

Exposed system fastener selection guide

For exposed fastener systems, SFS offers products for a variety of different applications. The Woodgrip metal to wood fasteners are ideal for exposed systems installed into wood, plywood, and OSB decks. The Impax self-drilling or self-tapping lines are ideal for metal deck applications. The SFS website features a number of selection guides in the education hub to help determine the correct fastener.

In addition, the SFS Fastener Color Selection Tool allows users to select the appropriate fastener color based on the panel manufacturer, panel color, and panel color code. This tool makes the selection process considerably easier for customers, and ensures the least intrusive appearance for exposed systems.

Standing seam fastener and clip selection guide

SFS offers both fasteners and clips for standing seam systems. The Panel Clip Finder Tool provides an easy method to ensure the proper clip is selected for each specific metal panel. The selection is based on the manufacturer, machine type, and panel type. There are also a number of clip screws available, which are selected based on compatibility with the material of the roof deck. The SFS education hub has a number of useful resources to ensure customers select the correct fastener.

Have additional questions about choosing screw length or depth requirements? Members of the SFS team are ready to help. Call 610 376 5751 to consult with a specialist.