Putting exposed-fastener ag panel (29 gauge) on a barn roof that's 3:12.

Screw Placement (3:12 Slope):

• Field: Fasten in the flat of the panel (valley), not the high rib. On 3:12, water can capillary-draw up the rib; flat fastening seals better.
• Spacing: 12"–18" OC in the field (check manufacturer; 12" is safer for 29ga). 6" OC at eaves, ridges, and endlaps (uplift zones).
• Fastener: #10 or #12 x 1"–1.5" pancake-head wood screw with EPDM sealing washer. Drive until washer compresses ~50%—don't overdrive (dimples panel) or underdrive (leaks).

Endlaps (Slope Direction):

• Minimum 6" overlap (IRC R905.10.3 / manufacturer spec).
• Run butyl tape sealant (3/32" x 3/8") on the lower panel's top flat, 1" from the edge, before setting upper panel.
• Stitch-screw the lap: 6" OC through both panels in the flat, 1" from the lap edge. Do not rely on main purlin screws alone here.

Sidelaps (Side-to-Side):

• One corrugation minimum (usually ~9"–12" coverage).
• Apply butyl tape on the underlap's rib shoulder.
• Stitch-screw 12"–18" OC through the sidelap rib (or flat if profile allows) to clamp the seal.

Critical Details:

• Eave: Install closure strips (vented or solid + vented ridge) + butyl tape under panel. Screw 6" OC.
• Ridge: Vented closure + ridge cap. Screw cap 12" OC into panel flats.
• Trim: All flashing (rake, valley, sidewall) requires butyl tape behind it and stitch screws 12" OC.

Code/Standard: IRC R905.10 (Metal Roof Panels), manufacturer's installation instructions (governs per R905.10.1). 29ga on 3:12 is minimum slope for lapped panels (IRC Table R905.10.3(1)).

Pro Tip: Chalk lines for screw lines. Sweep metal shavings daily—rust streaks fast. If purlins are >24" OC, use 26ga or add purlins; 29ga spans max 24" typically.

For a 29-gauge exposed-fastener AG panel on a 3:12 barn roof, follow these practical, code-aligned steps:

Screw Placement:

• Install screws through the high ribs (not the flat pan) to ensure proper sealing and structural engagement.
• Space screws 12 inches on center along each rib at the eaves, ridges, and ends.
• In the field (middle of panels), space screws 24 inches on center along each rib.
• Use #10 or #12 self-drilling screws with EPDM-bonded washers (minimum 5/8" diameter) rated for metal roofing.
• Drive screws perpendicular to the panel until the washer compresses slightly — do not over-torque (risk of washer damage or panel dimpling).
• At panel ends and laps, place screws within 1 inch of the edge to secure the overlap.

Lap Treatment:

• Side laps: Overlap panels by at least 2 inches (standard for AG panels). Fasten through both panels at the high rib of the overlap, following the screw spacing above. Apply a continuous bead of approved butyl tape sealant under the lap before fastening — this is critical for water shedding at 3:12 pitch.
• End laps: Stagger end joints by at least 24 inches. Overlap by 6–8 inches, seal with butyl tape under the lap, and fasten through both panels every 12 inches along the overlap.
• Flashings: Use compatible metal flashings at ridges, eaves, and valleys. Seal all laps and penetrations with butyl tape or approved roofing sealant.

Important Notes:

• 3:12 is the minimum slope for exposed-fastener metal roofs per IBC 1507.4 and manufacturer specs (e.g., MBCI, Fabral). Do not go lower.
• Ensure roof sheathing is solid (plywood/OSB or spaced sheathing per manufacturer) to prevent oil-canning.
• Always follow the specific panel manufacturer’s installation guide — variations exist.
• If unsure about structural capacity or flashing details, consult a licensed contractor or engineer.

This method ensures weather tightness and longevity at low slope. Over-tightening or skipping sealant is the #1 cause of leaks.