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26. Weatherproofing & Flashing

Learning objectives

  • Flash penetrations correctly by roof type.
  • Use sealants as a supplement, not a substitute.
  • Lay out arrays to satisfy fire-code access and setbacks.

26.1 Flashing is the leak defense

Flashing: sheet-metal (or formed aluminum) integrated into the roof covering at a penetration point so water sheds over the metal rather than into the hole. It is a mechanical water barrier, not a sealant.

Roof penetrations are the leading source of post-installation leaks (Ch 7.2), so flashing is craft-critical. The method depends on the roof covering:

  • Shingle: a metal flashing slides under the shingle course above the penetration and over the course below, so water sheds over it; the attachment bolt is sealed within.
  • Tile: tile-replacement flashings or properly sealed tile hooks maintain the water course.
  • Metal/standing-seam: non-penetrating clamps avoid the problem; penetrating types use butyl/sealing washers.

Sealant (polyurethane/butyl) supplements flashing: it never replaces it. A bead of caulk over an unflashed hole is a future leak, not a seal.

26.2 Fire-code layout (IFC access and setbacks)

AHJ (Authority Having Jurisdiction): the governmental body or official responsible for enforcing a given code in a specific locality. The AHJ interprets requirements and may grant waivers.

The International Fire Code (IFC) dictates array layout for firefighter access, independent of the electrical design:

  • Access pathways (commonly 36 inches / 3 ft) and ridge setbacks to allow ventilation operations and roof movement.
  • Clear routes to emergency escape and rescue openings.
  • Exemptions: detached non-habitable structures (garages, carports, solar trellises), roofs at ≤2:12 slope, and cases where the AHJ waives requirements because rooftop operations won’t be used.

⚠️ These setbacks reduce usable roof area and must be factored into array sizing (Part IV). Discovering them at plan review forces a redesign.

26.3 Flashing and fire setbacks, drawn

 SHINGLE FLASHING (side view)        IFC ROOF LAYOUT (top view)
                                     ┌───────── ridge ─────────┐
  shingle above ─┐                   │ ▒▒▒setback▒▒▒(to ridge) │
       ══════════╪═════              │  ┌───────────────────┐  │
  flashing ►  ▓▓▓│▓▓▓  ◄ slides      │  │      ARRAY        │  │
       ══════════╪═════    UNDER     │  │                   │  │
  shingle below ─┘  bolt sealed      │  └───────────────────┘  │
                    within           │ ▒▒▒ 3 ft access path ▒▒ │
  water sheds OVER the flashing      └─────────────────────────┘

Flashing slides under the upslope course so water sheds over it; sealant only supplements. The IFC reserves ~3 ft access pathways and ridge setbacks for firefighters, and that area comes off your usable roof in sizing (Part IV).

Chapter 26 summary

Flash every penetration by the covering’s method (under-course on shingle, replacement flashing on tile, clamps on metal), with sealant only as a supplement. Lay arrays to the IFC’s access pathways (~3 ft), ridge setbacks, and escape-opening routes (accounting for the lost roof area in sizing), unless an exemption or AHJ waiver applies.

  • Flashing: sheet-metal barrier integrated into roof covering at penetrations so water sheds over it rather than into the hole.
  • IFC (International Fire Code): the model fire code governing array layout, access pathways, and ridge setbacks for firefighter operations.
  • AHJ (Authority Having Jurisdiction): the local official who enforces code and may grant waivers to standard requirements.
  • Access pathway: the ~36-inch-wide clear corridor the IFC requires around and between array sections for firefighter roof access.
  • Ridge setback: the required clear distance between the uppermost array edge and the roof ridge.
  • Tile-replacement flashing: a dedicated flashing unit that replaces a tile at a mounting point, maintaining the roof’s water course.

Full definitions: Appendix A (glossary).

Practice Problems: Chapter 26

  1. On a shingle roof, which way does flashing route relative to the shingle courses, and why?
  2. True or false: a generous bead of sealant over a roof bolt is an acceptable substitute for flashing.
  3. Roughly how wide are typical IFC firefighter access pathways?
  4. Name two situations that exempt a project from IFC access/setback requirements.
  5. Why must fire-code setbacks be considered during array sizing, not just at install?

Solutions: Chapter 26

  1. The flashing tucks under the upslope (higher) course and over the lower one, so water sheds over it rather than into the penetration.
  2. False. Sealant supplements but never replaces mechanical flashing; caulk over an unflashed hole is a future leak.
  3. About 36 inches (3 ft).
  4. Any two of: detached non-habitable structures (garages/carports/trellises), roofs at ≤2:12 slope, or an AHJ waiver when rooftop firefighting won’t be used.
  5. Setbacks reduce usable roof area, so the achievable array size (Part IV) shrinks; discovering them at plan review forces a redesign.

PART V & VI: CONSOLIDATION

You can now make a design legal and buildable: apply the electrical theory and service types (Ch 20), navigate the NEC by adopted edition and its key Article 690/705/706 sections (Ch 21), execute grounding, bonding, and rapid shutdown correctly (Ch 22), place overcurrent protection, wiring methods, disconnects, and labels (Ch 23), attach to any roof type (Ch 24), satisfy ASCE 7 structural loading (Ch 25), and keep the building weather-tight and fire-code compliant (Ch 26). The design is now installable, inspectable, and safe.

Part VII turns to the human side of safety (the OSHA, electrical, and battery-fire practices that keep installers alive) before Part VIII walks the physical installation itself from site survey through commissioning.

Solar is dangerous work: heights, live electricity that can’t be switched off, and increasingly batteries that can burn. This part is the one where mistakes cost lives, not redlines. Safety thresholds here were verified against OSHA and NFPA sources in mid-2026; OSHA standards are federal but state-plan states may add requirements, so confirm yours.