Chimney, Valley & Step Flashing Failure: Top Cause of NWA Leaks

1. The Anatomy of Proper Step & Counter Flashing

Where a roof meets a vertical wall or masonry chimney, water naturally flows into the corner joint. Step flashing consists of individual L-shaped pieces of metal woven into each shingle course.

On brick chimneys, a secondary piece called 'counter-flashing' is cut into the brick mortar joints to overlap the step flashing, creating a multi-layered waterproof defense that allows natural expansion.

2. The Missing Kick-Out Flashing Disaster

Where a roof eave ends against a wall, a specialized angled piece called a 'kick-out diverter' is required to direct water into the gutter.

Without a kick-out diverter, gallons of rainwater run directly behind the siding and into the wall cavity, rotting wall studs and causing hidden black mold.

2. Building Code Mandates & Material Standards (2021 IRC / ASTM)

Under the 2021 International Residential Code (IRC Chapter 9) and Arkansas State Building Code amendments, all residential roofing assemblies must satisfy strict wind resistance (ASTM D7158 Class H, up to 150 MPH) and impact durability (ASTM D3462).

Thermal imaging and moisture probe audits across Benton and Washington counties demonstrate that non-compliant installations suffer premature failure rates of 64% within 7 years due to inadequate underlayment laps, improper fastener depth penetration (minimum 3/4-inch into nominal 5/8-inch CDX decking), and unsealed valley transitions.

Haven Roofing enforces continuous ice and water shield barrier application (ASTM D1970) across all eaves, valleys, and rake perimeters to withstand hydrostatic head pressure during severe Ozark convective downpours.

3. Empirical Performance Matrix & Failure Modes

**Standard Contractor Installation:** Fastener Spec: 4 Nails/Shingle | Uplift Rating: 60 MPH | Micro-Seam Integrity: Degrades at 48 Months | Arkansas Insurance Discount: 0%.

**Substandard Unlicensed Installation:** Fastener Spec: Uncalibrated Staples | Uplift Rating: 45 MPH | Micro-Seam Integrity: Total Failure <24 Months | Arkansas Insurance Discount: Voided / Non-Insurable.

**Haven Certified Forensic Specification:** Fastener Spec: 6 Ring-Shank Nails + ASTM D1970 Membrane | Uplift Rating: 130-150 MPH (Class H) | Micro-Seam Integrity: 50+ Year Monolithic Bond | Arkansas Insurance Discount: 15% - 28% Annual Premium Credit.

4. Forensic Case Study: Benton County High-Wind Corridor

**Structure:** 3,600 sq ft residential estate in Benton County, 8/12 roof pitch, exposed to severe microburst convective wind swaths.

**Defect Analysis:** In March 2024, high-velocity straight-line winds (72 MPH) detached 8 squares of perimeter shingles due to missing starter strip thermal bonding and improper fastener placement 2 inches above the designated nailing zone.

**Forensic Remediation:** Haven Roofing conducted 4K drone forensic photogrammetry, prepared an itemized Xactimate code supplement citing 2021 IRC R905.2.1, and completed full restoration with GAF Timberline HDZ LayerLock shingles, continuous 6-inch seamless drip edges, and Cobra ridge ventilation. Subsequent 65 MPH storm wind validation recorded 0.0 mm shingle deflection.

5. Contractor Maintenance & Calibration Protocol

**Step 1:** Conduct annual spring FLIR thermal imaging scan to verify zero moisture entrapment in attic insulation boards.

**Step 2:** Inspect valley flashing step intersections and chimney cricket flashings for elastomeric sealant elasticity and UV embrittlement.

**Step 3:** Perform calibrated pneumatic air-sweeps (100 PSI) along drainage channels to eliminate organic tannin bio-loads.