Materials & Technical Execution Standards

In Accordance with The Wildfire Trades Guild (WTG) Certification Framework

To achieve Guild Accreditation, all structural retrofits, land management practices, and site installations must strictly comply with the following material specifications and operational standards. These benchmarks exceed standard WUI (Wildland-Urban Interface) municipal codes to ensure maximum structural survival and ecosystem resilience.

1. Flashing & Corrosion-Resistant Metal Assemblies

• Material Composition: Minimum 26-gauge galvanized steel, 16 oz/sq ft cold-rolled copper, or 0.032-inch thick corrosion-resistant aluminum. Bare or un-coated mild steel is strictly prohibited.

• Deck-to-Wall Flashing: Continuous L-flashing paired with a self-adhering high-temperature ice/water membrane extending at least 6 inches vertically behind cladding and 6 inches horizontally across deck ledgers.

• Drip Edge Flashing: Metal drip edges installed along all eaves and gables, extending into the gutter to prevent ember intrusion into the fascia and sub-fascia gaps.

• Valley Flashing: Minimum 24-inch wide W-bend or V-bend metal valley flashing lined with high-temperature underlayment across all roof intersections.

• Chimney & Vent Step Flashing: Individual metal step flashings interwoven with roofing courses at all vertical wall/chimney penetrations, sealed with non-combustible elastomeric sealant.

2. Mesh & Ember-Proof Barrier Systems

• Aperture & Wire Size: Corrosion-resistant mesh with openings no larger than $1/8\text{ inch}$ ($3.2\text{ mm}$), constructed from minimum 20-gauge wire. Standard $1/4\text{ inch}$ hardware cloth is prohibited for ember defense.

• Alloy Requirements: Grade 304 or 316 stainless steel, heavy-gauge copper, or coated expanded metal. Uncoated steel and aluminum mesh (susceptible to low-melting-point failure) are banned in high-heat exposure zones.

• Foundation & Crawlspace Vents: Direct replacement or retrofit using Guild-approved dual-stage ember vents (e.g., baffle/intumescent-mesh hybrid systems) that seal automatically under direct thermal radiation.

• Deck Sub-Structure Screening: Continuous mesh enclosure along all open deck undersides, joist bays, and low-clearance perimeter foundations.

• Gutter Guards: Heavy-duty, micro-mesh stainless steel gutter covers engineered to shed dry debris while preventing ember ignition of accumulated needle cast.

3. Cement Boards & Non-Combustible Fiber Cladding

• Standard Compliance: All fiber-cement panels, lap siding, and soffits must comply with ASTM C1186 (Grade VIII) and pass ASTM E1354 cone calorimeter testing with zero flame propagation.

• Thickness & Profile Requirements: Minimum $5/16\text{ inch}$ thickness for lap siding and panel assemblies; minimum $7/16\text{ inch}$ for heavy-duty structural trim and corner boards.

• Ground-to-Cladding Clearance: Mandatory $6\text{-inch}$ vertical clearance between the bottom edge of fiber-cement cladding and exposed earth/hardscape to create a non-combustible splash zone.

• Joint Sealing & Backing: All vertical and horizontal butt joints must be backed with flashing or non-combustible joint covers and sealed with fire-rated elastomeric joint sealant.

4. Fire-Retardant-Treated (FRT) & Fire-Resistant Timber

• FRT Pressure-Treated Wood: Must meet AWPA (American Wood Protection Association) U1 and C20/C27 standards for exterior applications (marked as "Exterior Type FR-S"), exhibiting a flame spread index of 25 or less under ASTM E84 testing.

• Heavy Timber / Mass Timber Assembly: Heavy timber construction with minimum nominal dimensions of $6\times 6$ for posts and $4\times 8$ for beams, leveraging inherent char-layer thermal resistance where solid timber is specified.

• Ignition-Resistant Hardwoods: Naturally dense hardwoods (e.g., Ipe, Cumaru, Massaranduba) certified under ASTM E84 Class A criteria, pre-approved for exposed decking and framing.

• Prohibited Lumbers: Un-treated cedar, redwood, pine shake, and standard pressure-treated SYP (Southern Yellow Pine) within Zone 0 ($0\text{–}5\text{ ft}$) and Zone 1 ($5\text{–}30\text{ ft}$).

5. Perimeter Fencing, Gates & Attached Structures

• Non-Combustible Zone 0 Attachment: The final 5 feet ($1.5\text{ m}$) of any fence or gate attaching directly to a structure must be constructed entirely of non-combustible materials (e.g., wrought iron, powder-coated steel, aluminum, or masonry).

• Gate Hardware & Latching: Self-closing, heavy-duty metal hardware designed to maintain structural closure during wind-driven ember storms.

• Metal Mesh Infill Gates: Heavy-gauge steel framing with stainless steel or expanded metal mesh infill for perimeter gates requiring air flow without compromising ember resistance.

• Post Foundation Anchor: All posts within 30 feet of a primary structure must be anchored into concrete piers with steel standoff brackets to isolate timber from soil moisture and leaf litter accumulation.

6. Intumescent Paints, Fire-Retardant Coatings & Sealants

• ASTM E84 / Class A Intumescent Paint: Water-based or solvent-based intumescent coatings tested to yield a Class A flame spread rating on structural wood substrate, expanding into an insulating char layer upon heat exposure.

• Clear Exterior Retardant Sprays: Non-toxic, leaching-resistant clear retardants certified for exterior siding and structural timber treatment (must undergo 168-hour accelerated weathering tests).

• Firestop Caulks & Elastomeric Sealants: High-velocity ember-blocking sealants complying with ASTM E814 / UL 1479 for sealing siding gaps, utility wall penetrations, and soffit-to-wall interfaces.

7. Wildfire-Resilient Landscaping & Zone 0–1 Planting

• Zone 0 ($0\text{–}5\text{ ft}$) Hardscape Mandate: Total prohibition of organic mulches, bark, dry peat, or flammable shrubs. Only non-combustible materials (decomposed granite, river rock, gravel, pavers, or concrete) are permitted.

• Fire-Defensive Plant Selection: High-moisture content, broadleaf species with low resin/volatile oil content, non-pyrophytic root systems, and low leaf-litter dropping characteristics.

• Plant Spacing & Clustering: Isolated planting islands in Zone 1 ($5\text{–}30\text{ ft}$) separated by horizontal gaps of at least 2 to 3 times the height of the mature plant canopy.

• Organic Mulch Restrictions: Shredded cedar ("gorilla hair") and pine bark mulches are strictly banned within 30 feet of any structure. Coarse wood chips permitted only in Zone 2 if separated by gravel firebreaks.

8. Tree Care, Canopy Management & Wildland Forestry

• Vertical Crown Ladder Clearance: Lower branch pruning to a minimum height of 6 to 10 feet from the ground (or $1/3$ the total tree height for younger trees) to eliminate ladder fuels.

• Horizontal Canopy Separation: Minimum 10 to 15 feet of clearance between mature crowns in Zone 1, scaling up to 20+ feet on steep slopes (>20% gradient).

• Roofline Canopy Separation: Mandatory 10-foot minimum physical clearance between any tree branch/canopy and roof structures or chimney outlets.

• Snag & Hazardous Tree Removal: Removal of all dead, dying, or diseased standing trees (snags) within striking distance of structures, power lines, or access routes.

• Biomass Utilization: Mandated on-site mastication, chipping, biochar conversion, or off-site biomass hauling. Unprocessed slash piles left on-site are prohibited.

9. Dedicated Fire Suppression Cisterns & Water Infrastructure

• Storage Capacity Metrics: Minimum 2,500-gallon dedicated draft tank for single-family residential properties; 5,000 to 10,000+ gallons for rural/off-grid parcels.

• Tank Construction Materials: Heavy-gauge subterranean or above-ground steel tanks, cast-in-place concrete, or UV-stabilized heavy-duty polyethylene wrapped in thermal heat shields.

• National Standard Fitting & Hydrant Valves: Mandatory 4.5-inch or 2.5-inch NH/NST brass or stainless steel draft valves (dry hydrants) positioned for easy access by local fire apparatus.

• Dedicated Standalone Pumps: High-pressure gas-powered pump systems ($200+\text{ GPM}$ at $100\text{ PSI}$) isolated from municipal power grids, complete with heat-shielded fuel delivery and auto-start features.

10. Fire-Rated Roofing Assemblies & Underlayment

• Class A Roof Coverings: Universal requirement for Class A assemblies, including concrete tile, slate, metal standing seam, fiber-cement shingles, or Class A asphalt composition shingles.

• Non-Combustible Underlayments: Secondary protective layer consisting of high-temperature synthetic underlayments or fiberglass cap sheets complying with ASTM E108 Class A standards.

• Bird-Stop Cap Installations: Mandatory installation of non-combustible metal, mortar, or continuous eave closures ("bird stops") at the eave edges of barrel tile or corrugated metal roofs to block ember entry.

• Valley & Chimney Metal Linings: Double-underlaid valley channels reinforced with continuous metal valley caps.

11. Exterior Rooftop Sprinklers & Active Foam Systems

• Nozzle & Hardware Construction: Corrosion-resistant brass, bronze, or stainless steel impact/rotary impact sprinkler heads capable of full 360-degree coverage across roof planes and surrounding Zone 0 defensible space.

• Thermal Sensors & Automated Activation: Dual-stage triggering mechanism utilizing ambient thermal sensors, rate-of-rise heat detectors, or cloud-activated remote controllers with manual overrides.

• Supply Piping Lines: Rigid copper, stainless steel, or schedule 80 steel exterior piping runs. Exposed PVC, CPVC, or flexible plastic piping is strictly prohibited on exterior surfaces.

• Class A Compressed Air Foam (CAFS) Integration: Optional automated injection systems delivering Class A fire-retardant foam, providing an insulated thermal gel layer over roof and deck surfaces prior to ember arrival.