A standing seam metal roof is a popular roofing option for both residential and commercial buildings. It gets its name from the raised vertical seams that run down the length of the roof panels. These seams are where the metal roof panels interlock together to form a water-tight seal. But how exactly are standing seam metal roof panels attached to the roof structure?
Overview of Standing Seam Metal Roof Attachment
Standing seam metal roof panels are attached to the roof deck or substrate (typically plywood or OSB board) using concealed clips that are fastened to the roof structure. The clips fit over the male and female seams of adjoining panels to hold them in place while still allowing them to expand and contract with temperature changes. This is known as the floating clip method. An alternative is to use fixed clips that do not allow for panel movement.
There are several components involved in properly attaching a standing seam metal roof:
- Metal roof panels
- Clips – concealed floating or fixed
- Fasteners for the clips
- Sealant or tape for the seams
- Trims and flashings
The specific approach will vary slightly depending on the metal roof product being installed. But the basic concept is similar across the major standing seam metal roof types.
Standing Seam Metal Roof Panel Types
There are three main types of standing seam metal roof panels:
- Snap-Lock Seam – These have an overlapping male/female seam that snaps together.
- Mechanical Seam – The seams interlock and are crimped together by a seaming machine.
- Folding Seam – Panels are designed to be folded over one another and interlocked.
Mechanical seams are the strongest and most watertight. But any of these can be installed successfully if done properly.
Attachment Methods by Panel Type
Snap-Lock Standing Seam
Snap-lock standing seam panels are easy to align and snap together. The concealed clips fit over the seams to hold them in place. Here are the steps to attach them:
- Install any insulation, thermal blocks, or sub-framing required.
- Attach metal substrate boards (typically plywood or OSB) to the roof deck.
- Place starter clips at the eave to hold the first panel edges.
- Fit the snap-lock panel edge into the starter clips.
- Install concealed clips onto the substrate at the designated spacing.
- Align seams and press adjoining panels together to lock in place.
- Add seaming tape or sealant if needed.
- Install ridge caps and trims.
The concealed clips for snap-lock seams are available as floating or fixed attachment. Floating clips allow slight panel movement. Fixed clips hold the panels rigidly in place.
Mechanically Seamed Standing Seam
Mechanically seamed panels take more skill to install. The process is:
- Install any insulation, thermal blocks, or sub-framing required.
- Attach metal substrate boards to the roof deck.
- Place starter clips at the eave to hold the first panel edges.
- Fit the panel edge into the starter clips.
- Temporarily clamp panels at the seams.
- Install concealed clips onto the substrate at the designated spacing.
- Remove clamps and interlock panel seams.
- Use a powered seaming machine to crimp the seams together and create a watertight closure.
- Add sealant if needed.
- Install ridge caps and trims.
The seaming machine applies pressure and folds the seam over itself. This creates a very strong and weather-resistant joint. Floating clips are typically used with mechanical seams.
Folding Seam Standing Seam
Folding seam panels are designed to be folded over one another. The installation process is:
- Install any insulation, thermal blocks, or sub-framing required.
- Attach metal substrate boards to the roof deck.
- Place starter clips at the eave to hold the first panel edges.
- Fit the panel edge into the starter clips.
- Install concealed clips onto the substrate at the designated spacing.
- Fold over the seam, locking the panels together.
- Install ridge caps and trims.
The folding action creates a tight seam. Floating or fixed clips can be used with folding seam panels. The folding process may be done by hand or with a manual folding tool for a more consistent seam.
Standing Seam Metal Roof Clip Types
There are two main categories of clips used to attach standing seam metal roof panels – fixed and floating. Floating clips are more common for allowing panel expansion and contraction. But fixed clips provide a rigid attachment.
Floating Clips
Floating clips, as the name implies, allow the roof panels to float and move slightly. The ability to expand and contract with temperature changes reduces stress on the panels and fasteners. This helps prevent oil canning and noise from thermal movements. There are two main types of floating clips:
- Anchor Clips – Attached at the top edge of panels to anchor them in place while allowing movement at the seam. Often used at eaves, ridges, and ends.
- Slider Clips – Fit over the seams between panels and slide horizontally over the seam. Allow for expansion and contraction movement.
Floating clips are typically attached with fasteners that allow slight movement as well, such as slotted or oversized holes.
Fixed Clips
Fixed clips hold the standing seam metal panels rigidly in place. They do not allow the panels to move and expand/contract freely. The main types of fixed clips include:
- Single Fixed Clips – Attach at one point on the panel seam.
- Two-Piece Fixed Clips – Use two pieces to lock the seam in place.
- Stiffened Clips – Have a rigid back that resists panel movement.
Fixed clips can put more stress on panels and fasteners due to restricted movement. But they provide a very rigid attachment. Fasteners are typically installed tight with no movement allowed.
Standing Seam Metal Roof Fastener Types
Choosing the right fasteners is critical for properly attaching standing seam metal roof clips and trims. The most common fastener options include:
Screws
Screws are commonly used to attach both clips and trims. They can have special coatings or be made of stainless steel for corrosion resistance. For floating clip systems, they may have oversized or slotted holes to allow movement.
Rivets
Rivets provide a very secure fastener option. Roofing rivets are available with sealant fill for weather-tightness. They allow little or no movement so are used with fixed clips or trims.
Nails
Ring shank or spiral nails are an economical option for attaching some types of clips or trims, especially in non-coastal areas. They provide less holding power than screws or rivets though.
In coastal or high-wind regions, stronger fasteners like screws or rivets are recommended. The clip manufacturer will often specify the type, material, and spacing of fasteners to use.
Standing Seam Metal Roof Seam Sealants
Sealants or tapes can be used to waterproof the seams and prevent leakage. Options include:
- Tube Sealants – Applied manually to the seams after interlocking the panels. Caulking grade butyl sealant is common.
- Pressure Sensitive Tapes – Special waterproofing tapes can be applied to the seams.
- Factory-Applied Seals – Some panels have sealants applied in the factory.
Sealants and tapes are an optional added measure on most standing seam metal roofs. But they are required on some low-slope applications. The sealant adds redundancy if any moisture gets past the interlocked seams.
Standing Seam Metal Roof Ridge Caps
Ridge caps provide a finished look and waterproofing at the roof peak. Metal ridge caps match the panels and utilize similar attachment methods. They often overlap the panel seams and get fastened through the panels into the deck. Endwalls and hips also often use metal caps.
Standing Seam Metal Roof Valley Flashings
Valley flashings help waterproof and reinforce the valleys where roof planes come together. Open valleys are typically lined with a continuous metal flashing that the abutting roof panels get attached over. Closed valleys have panels tightly seamed over the valley.
Standing Seam Metal Roof Eave Trims
Eave trims provide an enhanced look at the lower roof edge. More importantly, they secure the panel edges. The trim gets installed first and the roof panels fit into it to anchor them. Fascias may also be installed for appearance.
Standing Seam Metal Roof Gable Trims
The ends of gable roofs are trimmed out with metal pieces attached over the panel edges. These match the roof panels and provide a neat finished appearance.
Standing Seam Metal Roof Penetration Flashing
Pre-formed flashings are used any time the roof is penetrated, such as around vent pipes. These sealants prevent leaks where panels are cut.
Special Considerations for Coastal and High Wind Areas
In coastal or high wind regions, some special precautions should be taken when attaching standing seam metal roofs:
- Reduce clip spacing for added holding strength.
- Use fixed clips instead of floating clips to resist wind uplift forces.
- Install tape or sealant on all seams and trims for added leak protection from wind-driven rain.
- Use stainless steel or corrosion-resistant fasteners.
With proper design and installation suited for the conditions, standing seam roofs can still perform very well near the ocean or in windy areas.
Conclusion
Attaching a standing seam metal roof properly involves several components working together. The panels are overlapped or folded and interconnected. Clips then fit over the seams to hold panels in place while allowing expansion and contraction. Sealants can be added for increased weather-tightness. With quality materials and correct installation, a standing seam metal roof can provide many years of trouble-free service.