Installing solar panels on a pitched roof requires a mix of precision, safety awareness, and understanding of both structural and electrical requirements. Let’s break down the process step by step, focusing on practical details that often get overlooked in generic guides.
**Pre-Installation Prep**
Start by assessing the roof’s condition. Check for rot, loose shingles, or weak spots—these must be repaired *before* mounting anything. Use a moisture meter if you suspect water damage. Next, confirm the roof’s load-bearing capacity. Most pitched roofs can handle solar arrays, but older homes might need reinforcement. A structural engineer can provide clarity here.
For tools, you’ll need a torque wrench (calibrated to manufacturer specs), roofing anchors rated for your climate, lag bolts, sealant compatible with your roofing material (e.g., polyurethane for asphalt shingles), and a tilt-and-swivel mounting system. Don’t skimp on safety gear: harnesses with dual lanyards, toe boards, and a stable scaffold system are non-negotiable.
**Mounting Hardware Placement**
Layout is critical. Use a chalk line to mark rafter locations—stud finders often fail here, so a thermal imaging camera or drilling small pilot holes to confirm rafter spacing (typically 16″ or 24″ on-center) works better. Align rails parallel to the roof ridge, maintaining a 6-12″ gap from edges to prevent wind uplift issues.
When attaching flashing mounts, apply sealant *under and around* the base to prevent leaks. Tighten bolts to the manufacturer’s torque settings—over-tightening cracks tiles, while under-tightening risks loosening over time. For tile roofs, use specialized hooks that slide under tiles without breaking them; for metal roofs, clamp-based systems avoid penetrations.
**Rail and Panel Installation**
Secure rails to mounts using stainless steel clamps, ensuring they’re level with a laser or water level tool. Even a 1° tilt mismatch can cause uneven weight distribution. Slide panels onto the rails, starting from the lower edge and working upward. Leave a ¼” gap between panels for thermal expansion—tight fits lead to microcracks during temperature swings.
Use mid-clamps and end-clamps specific to your PV module frame thickness. Misaligned clamps stress the frame and void warranties. For steep roofs (over 30°), temporary brackets or suction handles help hold panels in place during mounting.
**Electrical Wiring and Grounding**
Run conduit along rails, securing it with UV-resistant zip ties. Keep DC wiring 12″ away from roof edges to meet NEC 690.31 code. Use polarity-checked MC4 connectors—reverse polarity can fry inverters. Ground all rails and panels with copper wire (6 AWG minimum), bonding them to the home’s main grounding system.
Label every wire at both ends (e.g., “String 1, Panel 3”) for future troubleshooting. If using optimizers or microinverters, test each unit with a voltage meter before closing the circuit—defective units often show 0V output even if LEDs appear normal.
**Final Checks and Compliance**
After mounting, perform a tug test—gentle pressure on panels to confirm no movement. Inspect seals for gaps; reapply sealant if you spot hairline cracks. Check local codes for fire setbacks (often 18″ from ridges and valleys) and emergency access pathways.
Document every step with photos—timestamps and geotags help if inspectors request proof. Finally, schedule a thermal scan within 48 hours of installation; hotspots indicate loose connections or faulty panels that need immediate replacement.
This process isn’t just about bolting panels to a roof. It’s a systematic blend of structural integrity, electrical precision, and proactive problem-solving—keys to a system that lasts 25+ years without hiccups.