Pole barn, 2:12 slope, 29-gauge exposed-fastener panels on 2x4 purlins at 24 inches.

This roof will leak, blow off, and rot the purlins. It violates the panel manufacturer’s instructions and IBC/IRC requirements for low-slope metal roofing.

1. Wrong Screw Location (Critical) Exposed-fastener panels (typically R-Panel/PBR) must be fastened in the flat of the pan (low rib), not the high rib.

• Rib screws: The panel cannot compress the washer against the steel; the rib flexes, the washer gaps, and water pumps in under the head. Wind uplift peels the panel off the screw shank.
• Code: IBC 1504.3.2 / IRC R905.10.5 require fasteners per the approved manufacturer’s instructions. No major manufacturer allows rib screws for primary attachment.

2. Insufficient Fastener Pattern 24" OC in the field is inadequate for 2:12 slope on 24" purlin spacing.

• Standard pattern: 12" OC at eaves/ridges/endlaps, 18"–24" OC in field (check specific panel ESR report).
• Low slope = higher uplift pressures (ASCE 7). Edge zones need tighter spacing.

3. Missing Side-Lap Stitch Screws

• Result: Capillary draw and wind-driven rain migrate between sheets. Panels "chatter" and fatigue at the lap.
• Fix: Stitch screws (typically #12 x 3/4") 12"–18" OC per manufacturer.

4. Unsealed End Laps (4" Lap)

• On 2:12, a 4" lap requires butyl tape/sealant between sheets. Without it, water capillaries uphill 4"+.
• Code: IBC 1507.4.3 / IRC R905.10.3 require sealant at endlaps for slopes < 3:12.

5. No Eave Closures

• Result: Wind-driven rain/blowing snow enters the building envelope. Birds/rodents nest in ribs. Panel ends flap and tear off.
• Fix: Solid outside closures (vented if unconditioned) + butyl tape.

6. 2:12 Slope Limitation

• Most exposed-fastener panels require minimum 3:12 (some 2.5:12 with sealant). At 2:12, you are likely outside the panel’s listing/ESR. You need a standing-seam system rated for low slope or a different roof assembly.

Immediate Action: Stop. Remove rib screws. Verify panel minimum slope. Re-install per manufacturer’s printed instructions (pan screws, stitch screws, sealant, closures) or switch to a listed low-slope system. This is not a "cosmetic" issue; it is a structural/weather barrier failure.

This installation is non-compliant and will likely fail prematurely due to multiple critical errors:

1. Screw Placement on Ribs (Top of Ribs): Exposed-fastener panels must be fastened through the flat of the panel, not the rib. Fastening on the rib compresses the panel, distorts the seal, and creates a direct path for water intrusion. This violates manufacturer instructions and IBC Section 1507.4 (metal roofing), which requires adherence to approved installation details.

1. No Stitch Screws at Side Laps: Side laps require stitch screws (typically every 12–24 in. o.c.) to prevent uplift and water infiltration. Without them, wind-driven rain will enter laps, especially at 2:12 slope (minimum for exposed-fastener panels is usually 3:12; 2:12 is below code minimum per IBC 1507.4.2 and most manufacturer specs). This slope is unsuitable for exposed-fastener systems without additional underlayment or sealant — which is absent here.

1. End Laps Only 4 Inches with No Underlayment or Sealant: End laps need a minimum of 6–8 inches (per IBC and manufacturers like MBCI, ASC Building Products) and must be sealed with butyl tape or sealant. Four inches is insufficient, and no sealant guarantees leaks.

1. No Closures at Eave: Eave closures (foam or metal) are required to prevent wind uplift, water intrusion, and pest entry. Missing closures violate IBC 1507.4.3 and invite catastrophic failure.

Result:

• Immediate and chronic leaks at laps and fasteners.
• Panel distortion and fastener withdrawal due to improper screw placement.
• Uplift failure in moderate wind (especially at low slope).
• Corrosion from trapped moisture at unsealed laps.
• This roof will leak within the first rain event and likely fail structurally within 1–2 years.

Corrective Action: Remove and reinstall per manufacturer’s ICC-ES report and IBC 1507.4. Use correct fastener placement, minimum 3:12 slope (or add ice/water shield underlayment if 2:12 is unavoidable), proper lap sealant, stitch screws, and eave closures. This is not a DIY fix — consult a licensed roofing contractor or engineer.

Note: 29-gauge is thin; improper fastening accelerates fatigue. Do not proceed as installed.