By Jennifer Kirstens · 2026-08-31 · 18 min read

Standing seam metal roofs are the ideal solar substrate: 50-year membrane life, no penetrations required, and the seam itself is a load-bearing feature. The tradeoff is clamp selection — the seam profile dictates the S-5! (or S-5!-equivalent) part, and getting the wrong clamp on the wrong seam is a common cause of failed pull tests. This guide maps every common seam profile to the correct clamp and rail from the PES catalog.

Before picking a clamp, take a phone photo of the seam and measure the seam height and width. The seam profile falls into one of six categories:

Once you have the right clamp on the seam, you have two paths: a traditional rail-based install, or S-5!'s rail-less PVKIT 2.0 direct-attach system.

PVKIT 2.0 removes the rail from the equation on standing-seam roofs. Each PVKIT hardware unit (usually one per module edge) sits on top of the S-5! clamp and acts as both mid-clamp and end-clamp depending on where the module sits in the row. Install time drops to ~4 min/module for experienced crews, and the roof stays completely penetration-free.

Every S-5! install should include at least one field pull test — the AHJ often requires it, and it validates that the seam material and setscrew engagement match the manufacturer's published values.

Standing seam metal roofs are slippery — snow slides fast, and wind load distribution across the seam clamps is more concentrated than on asphalt shingle. Design tips:

'Metal roof' is a category, not a product. Different metal-roof profiles carry different structural characteristics, different water-management schemes, and very different clamp compatibility. Standing seam is the premium, most-solar-friendly profile. Trapezoidal exposed-fastener panels are common on agricultural and industrial buildings and are compatible with a smaller clamp set. Corrugated is the low-cost commodity choice and needs the specialty CorruBracket line.

Standing seam panels are formed with vertical ribs (1.5–3 inches tall) that snap or mechanically seam together at the joint. There are no exposed fasteners on the flat panel — the seam itself is where two panels meet, and the seam provides the load path for solar clamps. Water sheds along the vertical rib with no penetration. The seam is what makes standing seam premium: 40–60 year membrane life, no exposed fasteners to corrode, and the ideal solar mounting substrate.

Trapezoidal / exposed-fastener panels (R-panel, PBR, U-panel) are the workhorses of steel-building construction. They use exposed color-matched screws every ~24 inches along each rib. Solar clamps that engage the trapezoidal rib (S-5-K Grip, ProteaBracket) sit above the seam without penetrating — but the roof itself has thousands of fastener penetrations, so the roof warranty is a shorter 15–25 year period. Still excellent for solar; just be aware of the different warranty math.

Corrugated panels (sinusoidal, 5V-Crimp, some architectural corrugated) have shallow rounded ribs that spread water shedding across the corrugation curves. Clamp options are limited: the S-5! CorruBracket is the primary attachment — a butyl-back saddle bracket that spans multiple corrugation peaks.

Every S-5! product has a seam-fit range spelled out in the datasheet. Field verification is non-negotiable — even 'standard' snap-lock profiles from the same manufacturer can vary ±0.1" in seam height between production runs. The three measurements you need before ordering:

1. Seam height from the top of the flat panel to the top of the seam. Measure with a caliper on 3–5 different seams. Common: 1.0", 1.5", 1.75", 2.0".
2. Seam width at the top of the seam (the horizontal dimension the clamp bites onto). Common: 0.15–0.25".
3. Panel spacing from seam to seam (center-to-center). Determines how many clamps you need per module row and how the mid-clamp geometry works. Common: 12", 16", 18", 24".

PES accepts field photos and dimensions via the Axis portal or by email to tech@pes.supply — turnaround for a clamp-fit verification is one business day. If we can't identify the profile with certainty from photos, we'll ask for a 24" panel offcut mailed in for direct measurement.

The rail-less install with PVKIT 2.0 is the fastest metal-roof solar install path — a well-drilled 3-person crew can hit 4–5 min/module on standing seam. Here is the sequence, from chalk to energized:

1. Layout and chalk. Measure the roof plane, mark seams, and chalk module row locations. Standing seam is dimensionally exact — no rafter locate is needed. Layout goes 3–5× faster than shingle install.
2. Deploy S-5! clamps. One clamp per seam per module column position. For portrait modules with a 40" width and 18" seam spacing, you need 3 clamps per module width. Torque setscrews per the S-5! spec (typically 130–160 in-lb for round-point on standing seam, 180 in-lb for dimple-point on trapezoidal).
3. Install PVKIT 2.0 mini-rails. Each PVKIT unit is a short aluminum bridge that spans between two adjacent S-5! clamps. Bolt PVKIT to the clamp top using the supplied bolt and t-slot fastener.
4. Mount first module. Set the module in place on top of the PVKIT units and slide the pre-installed module clamp inward against the module frame. Torque to 12 ft-lb.
5. Repeat for row. Each subsequent module slides in against the previous module's PVKIT clamp — this is where install speed comes from, since the mid clamp is already positioned by the previous module's end clamp.
6. Ground the array. S-5! clamps provide the module-to-module bonding via listed PVKIT hardware. One EGC from a designated rack lug to the array's AC junction or main service ground.
7. Perform pull test. After the first row is installed, pull-test one clamp to validate seam engagement (see the pull-test HowTo section).

While S-5! is the dominant clamp brand, PES stocks alternatives that fit specific use cases:

SnapNrack MetalMount is SnapNrack's answer to the standing-seam market — a proprietary seam clamp that mates directly with SnapNrack Series 100 rails via a slide-in geometry. Best for crews already standardized on SnapNrack for their asphalt-shingle jobs; skipping the S-5! interface saves an SKU line.

IronRidge Halo UltraGrip is a rail-less module clamp compatible with a limited set of standing-seam profiles. Attaches modules directly to a compatible seam clamp (typically S-5! or a Halo-branded clamp). Newer product line — expect more profile coverage over the next 12 months.

Unirac SolaHook Metal is Unirac's standing-seam clamp that interfaces with SolarMount rail. Similar functional envelope to the S-5! + XR100 combination but keeps the entire BOM inside the Unirac ecosystem.

For 90%+ of metal-roof jobs, S-5! remains the safe default — the widest seam-compatibility library, the largest pull-test dataset, and the deepest manufacturer relationships (every major panel OEM has issued a written S-5! compatibility letter).

Standing-seam solar has a different cost profile than shingle solar:

• No flashing. The single biggest cost savings — flashing on shingle is $8–$20 per attachment. Standing-seam has zero flashing.
• Fewer clamps than rail-based installs. A 24-module PVKIT install typically uses ~72 S-5! clamps (3 per module width). Same 24 modules on a rail-based install would use ~28 flashings + ~28 L-feet + 8 rails + 48 mid clamps + 24 end clamps.
• Higher clamp unit cost. S-5! clamps run $13–$17 each vs $2–$5 for an aluminum mid clamp on a rail system.
• Net cost. For a standard 8-kW system, the S-5! PVKIT approach is typically 10–20% cheaper on materials than a shingle equivalent, and 25–40% faster on install labor. The install-labor savings dominate.

Freight: S-5! clamps ship parcel-eligible in quantities up to about 200 clamps per carton. Above that, we ship LTL. PVKIT 2.0 kits ship parcel for a residential job. Total pallet count for a 24-module PVKIT install is typically zero — everything fits in 2–3 UPS boxes.

Every standing-seam roof manufacturer publishes an authorized-clamp list. Before ordering clamps for a specific job, get the current version of the manufacturer's letter — some brands limit acceptable clamps to only round-point setscrews (banning dimple-point on their profile).

Top-4 standing-seam manufacturers and their default S-5! authorization:

• AEP Span — approves S-5! S-5-U, S-5-U Mini, S-5-N, S-5-K Grip with round-point setscrews.
• McElroy Metal — approves S-5! S-5-U, S-5-N on Meridian; specifies torque range explicitly.
• PAC-CLAD (Petersen) — approves S-5! S-5-N and CorruBracket 100T on specified panel lines; authorizations by panel.
• Berridge Manufacturing — approves S-5-U, S-5-U Mini on Tee-Panel and Zee-Lock; check current spec for other lines.

Beyond seam profile, metal-roof substrates come in four material families, each with different S-5! clamp compatibility considerations:

Steel (Galvanized or Galvalume). By far the most common — 95%+ of standing-seam commercial roofs. G-90 galvanized or AZ-50 Galvalume coating provides 40–60 year corrosion protection. S-5! clamps are compatible with all steel substrates; setscrew torque follows the standard round-point spec.

Aluminum. Common on coastal buildings (salt-spray corrosion resistance) and premium architectural applications. Softer than steel — setscrew torque is typically reduced 10–15% to prevent dimpling the panel. S-5! publishes aluminum-specific spec sheets; always follow those instead of steel defaults.

Copper. High-end architectural (churches, historic restorations). Very soft — S-5! clamps typically use anti-crush pads. Torque reduced 25–30% vs steel. Verify with copper-panel manufacturer before install.

Zinc. European-heritage, growing in U.S. luxury architectural market. Similar softness profile to copper. VMZINC and RHEINZINK are the dominant brands. S-5! ProteaBracket is the primary clamp for European zinc trapezoidal profiles.

Standing-seam metal roofs shed snow fast — an entire winter's accumulation can avalanche off in one afternoon. Solar arrays on standing seam without snow retention above them face two risks: physical impact damage from sliding snow, and ice-dam pressure on the array edges.

S-5! sells a full snow-retention product line that integrates directly with PVKIT 2.0 installs:

• S-5! SnoBar. Aluminum crossbar mounted on S-5! clamps above the array. Retains snow load until it melts and drains through the array. Standard for snow-belt commercial installs.
• S-5! ColorGard. Color-matched aluminum snow retention panel system. Aesthetic-first, popular on high-end residential.
• S-5! DualGard. Two-bar system for extreme snow loads. Recommended for Pg ≥ 60 psf sites in the Rockies, upper Midwest, and northern New England.

Snow retention is designed by ground snow load and array orientation:

• P_g < 30 psf: snow retention optional, recommended only for foot traffic below
• P_g 30–60 psf: SnoBar single-bar above the array
• P_g 60–90 psf: SnoBar or ColorGard, verify with S-5! design tool
• P_g ≥ 90 psf: DualGard double-bar recommended

Real metal roofs aren't the flat rectangles that clamp-fit datasheets assume. Hips, valleys, and dormers create panel-layout wrinkles that need clamp-layout adjustments.

Hip roofs. Panels are cut at an angle where they meet the hip line. Clamps must sit at least 3" from the hip-cut edge to avoid clamp-to-cut-edge conflicts. On steep hips, this can reduce module count in the affected row. Design tool: hand-mark the hip on a scaled roof plan before layout.

Valleys. Panels drain toward the valley, and the valley itself is typically a formed metal channel. Never mount clamps on or immediately adjacent to a valley — the water flow will erode the setscrew coating. Set clamps at least 18" from valley centerlines.

Dormers, skylights, chimneys. Any rooftop feature that penetrates the standing seam needs 24" of clear space around it. Fire-code setback under IFC-2021 § 1204 will typically drive this dimension anyway.

Ridge caps. Modern standing seam usually has a ridge cap attached over the seam terminals. Clamps cannot sit on the ridge cap — set them in the last full-height seam below the cap.

Occasionally a pull test comes in below the S-5! published value. Diagnostic steps to identify the failure mode:

1. Verify setscrew torque. Re-torque the setscrews with a calibrated wrench. Loose setscrew is the single most common cause of below-spec pull test.
2. Check for seam material yielding. If the seam material has yielded (visible dimpling next to the setscrew), the seam is thinner or softer than the S-5! datasheet assumed. Options: switch to anti-crush setscrews (round-point with pad), reduce torque, or switch to a different clamp model.
3. Check clamp fit. Measure seam height and width; verify the clamp datasheet lists this profile as within range. Some seams (particularly hand-formed field seams) are outside standard range and require a custom-fit clamp.
4. Check panel gauge. Thin-gauge panels (24 gauge or thinner) may not develop full pull-test capacity even with a correctly-fit clamp. This is rare on modern commercial standing seam but common on legacy residential.
5. Escalate to S-5! engineering. For persistent below-spec pulls, S-5! provides free tech support and can specify a custom clamp or alternate attachment strategy.

The S-5! PVKIT 2.0 released in 2020 replaced the original PVKIT (2013–2020). Installers still occasionally encounter the original PVKIT on retrofit jobs or in old inventory. The two are functionally similar but incompatible — a PVKIT 2.0 rail bridge does not fit an original PVKIT clamp, and vice versa.

The 2020 refresh added:

• Wider module-frame compatibility (30–46 mm vs original 32–40 mm)
• Universal mid/end clamp geometry — the same clamp acts as mid or end depending on module position, cutting SKU inventory by 40%
• Improved UL 2703 grounding path via redesigned WEEB-style contact points
• Setscrew torque range narrowed for more consistent field results
• Powder-coat black finish added as a standard offering

PES stocks only PVKIT 2.0 as of 2024. Original PVKIT is no longer available new from S-5!. If you inherit an install with the original PVKIT and need to expand it, you have three options: (1) replace the existing clamps with PVKIT 2.0 (labor-intensive), (2) source original PVKIT from S-5! spare-parts service (limited stock, premium price), or (3) build the addition on a separate PVKIT 2.0 row and bond the two arrays through the electrical grounding system rather than via mechanical continuity.

Standing-seam roofs shed snow, but the array itself catches and holds snow until melting begins. The snow load ends up transferred through the module frames, through the mid clamps, through the rail (or PVKIT bridge), and into the S-5! clamps at the seam. From the seam, the load transfers into the roof panel and down through the roof structure.

The snow-load design chain has four checkpoints, and any one can be the limiting factor:

• Module frame — most modern modules are rated to at least 5400 Pa (113 psf) snow load, so this is rarely the limit.
• Mid clamp / rail (or PVKIT bridge) — spans between S-5! clamps must handle the distributed load. XR100 with S-5! clamps at 6 ft spacing handles 90 psf; tighter clamp spacing extends this to 120+ psf.
• S-5! clamp — the pull-out capacity at the seam is typically 1,200–2,100 lb depending on clamp model. Divide the peak uplift + snow drift force by clamp count to verify.
• Roof structure — the underlying trusses or purlins must accept the point loads at each clamp location. Structural PE review required.

For heavy-snow regions (P_g ≥ 60 psf), design typically ends up with:

• S-5! clamp spacing at 4 ft on the seam (from typical 6 ft interior)
• S-5-U or S-5-K Grip clamps rather than smaller Mini variants
• XR1000 rails rather than XR100 (or ProSolar R-184XD for the deepest section)
• Snow retention above the array (SnoBar or DualGard) to prevent avalanche onto modules

Roofing contractors have historically been cautious about solar on their standing-seam installs — a legitimate concern given the 40–60 year warranty period they're on the hook for. Coordination best practices:

Before installation, submit to the roofing contractor:

• Roof panel manufacturer's clamp approval letter (from S-5! datasheet cross-reference)
• Complete BOM with clamp part numbers and torque specs
• Array layout drawing showing every clamp location
• Pull-test plan (or pull-test results if pre-install pulls were performed)
• IFC-2021 § 1204 fire-code setback compliance drawing

Some roofing contractors will want to observe or perform the initial pull test themselves. This is legitimate and worth accommodating — a roofer who personally witnessed a 2,000-lb pull test on the specific seam is far more supportive of the array's presence over the next 40 years.

Post-install, provide the roofing contractor with:

• Photos of every clamp installed
• Signed torque log (clamp location, torque value, date, installer initials)
• As-built drawing showing final clamp locations

This documentation supports the roof warranty preservation and gives all parties a clean record if a leak or wear claim emerges years later. PES has a template torque log available through the Axis portal.