Metal Panel Types and Profiles
Standing seam versus through-fastened panel systems, steel versus aluminum substrates, gauge and thickness specifications, and protective coating systems including Galvalume and Kynar/PVDF.
- Compare standing seam and through-fastened panel attachment methods and state when each is appropriate
- Identify steel, aluminum, and copper as metal roofing substrates and list their properties
- Convert between gauge numbers and decimal thickness for common panel gauges (24, 26, 29)
- Describe Galvalume metallic coating and Kynar 500/PVDF fluoropolymer paint systems
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Standing Seam vs. Through-Fastened Panels
Two Fundamental Attachment Methods
Every metal roof panel system falls into one of two categories based on how the panels are secured to the structure: standing seam or through-fastened. The choice between them affects cost, performance, thermal movement capability, weather resistance, and appearance. The NRCA ProCertification exam tests your ability to distinguish between these systems and specify the correct one for a given application.
Standing Seam Panels
Standing seam panels interlock along raised seams (ribs) that stand 1 to 3 inches above the flat pan of the panel. The panels are secured to the structure using concealed clips - no fasteners penetrate the panel face. This concealed attachment is the defining feature of standing seam systems.
The raised seams are closed (seamed) using either a hand seamer or a powered roll-forming seam machine that travels along the seam length. Common seam profiles include single-lock (180-degree fold), double-lock (360-degree fold), and snap-lock (panels snap together without mechanical seaming).
Standing Seam
Attachment: Concealed clips - no exposed fasteners
Seam height: 1 to 3 inches above panel pan
Thermal movement: Floating clips allow panel expansion
Minimum slope: 1/4:12 to 3:12 (varies by profile)
Cost: Higher material and labor cost
Through-Fastened
Attachment: Exposed screws through panel face into purlins
Profile: Corrugated, ribbed, or trapezoidal
Thermal movement: Limited - screws restrict panel sliding
Minimum slope: 3:12 typical (varies by profile)
Cost: Lower material and labor cost
Standing seam advantages include superior weather resistance (no screw holes in the panel face), the ability to accommodate thermal expansion through floating clips, a cleaner appearance, and longer expected service life. Disadvantages include higher material cost, more complex installation, and the need for specialized seaming tools.
Through-Fastened Panels
Through-fastened (also called exposed-fastener) panels use self-drilling or self-tapping screws driven through the panel face and into the supporting purlins or deck below. The screws have neoprene or EPDM washers that compress against the panel surface to seal the screw penetration.
Through-fastened panels are less expensive and faster to install than standing seam. They are common on agricultural buildings, warehouses, self-storage facilities, and budget commercial structures. However, each screw hole is a potential leak point, and the neoprene washers degrade over time from UV exposure, requiring periodic maintenance.
Structural vs architectural standing seam:
Standing seam systems are further divided into structural and architectural categories:
- Structural standing seam panels span between purlins without a solid deck underneath. They carry their own weight plus live loads (snow, wind). Typically 22-24 gauge steel with deeper ribs (2-3 inches) for structural strength.
- Architectural standing seam panels require a solid deck (plywood or OSB) underneath for support. They are installed over existing roofing during re-roofing projects or on new construction with a solid substrate. Typically 24-26 gauge with lower ribs.
The exam may ask about minimum slope for each: structural standing seam can go as low as 1/4:12 (nearly flat) because the seam is watertight; architectural standing seam typically requires at least 3:12.
Standing seam panels use concealed clips with no exposed fasteners and accommodate thermal movement through floating clips. Through-fastened panels use exposed screws through the panel face and are less expensive but have limited thermal movement capacity. Structural standing seam can slope as low as 1/4:12; architectural standing seam typically requires 3:12 or greater.