Phronesis-Online

Wildfire Deck Mitigation — Commission Briefing Slide

The Three Principles

1. No direct fuel contact with the house (flashing, separations, breaks)
2. No ember entry points (mesh, enclosure, clearance, cleanliness)
3. No combustible mass within the 0–5 ft zone

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Critical Fixes for Decks

1. Deck-to-Wall Flashing

• Continuous metal flashing
• 2” vertical rise
• 1” horizontal overhang
• Eliminates wood-to-siding ignition path

2. Underside Enclosure (<4 ft)

• 1/8” metal mesh or non-combustible paneling
• Prevents embers collecting under deck
• Removes hidden ignition zone

3. Railing & Stair Interfaces

• 1” clearance OR flashing
• Stops fire travel along attached components

4. Fence Connection

• Metal flashing OR non-combustible break
• Wood fences act as fuse-lines unless interrupted

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Why This Matters

• 0–5 ft zone accounts for 80–90% of home ignition risk
• Embers travel miles; decks catch before vegetation
• These fixes collectively reduce deck ignition probability by >70% (IBHS WPH)

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What We Are Asking

Adopt or endorse this unified standard for deck mitigation:

• Flashing: 2” rise / 1” overhang
• 1/8” mesh for decks <4 ft
• 1” separation or metal break at all connections
• 6” ground clearance
• 0–5 ft non-combustible zone

This aligns Allstate + IBHS + NFPA + CalFire and provides a workable, local standard.