Warranty Call After Ventilation and Deck Deficiencies
Eighteen months after your firm installed a new asphalt shingle roof on a 1,800-square-foot ranch house, the homeowner reports that shingles are curling, granules are collecting in gutters, and ceiling stains appear near two bathroom exhaust fans. Your contract included a 10-year workmanship warranty and the manufacturer's 30-year limited shingle warranty. The attic has two gable-end vents but no soffit or ridge vents. Both bathroom fans discharge directly into the attic, and the attic insulation is blown up to the roof sheathing at the eaves. The roof was installed over the existing 1x6 skip sheathing with new 7/16-inch OSB, 15-pound felt, and no ice barrier at the eaves. The manufacturer's installation instructions require a minimum net free ventilation of 1 square foot per 150 square feet of attic floor area and prohibit nailing over skip sheathing without an approved deck. The homeowner says the prior roofer told him ventilation was 'not required for an old house.'
1. Diagnose the likely causes of the curling and leaks and allocate responsibility.
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The pattern points to moisture and ventilation problems, not a simple shingle defect. Two bathroom fans discharging into the attic add warm, moist air; the attic has only gable vents and no soffit or ridge vents, so it likely has poor cross-ventilation. Insulation blown against the roof sheathing at the eaves blocks any eave airflow and can cause condensation. Curling shingles, granule loss, and ceiling stains near the fans are consistent with trapped moisture and overheating.
The installation over skip sheathing is also a concern: the manufacturer prohibits it without an approved deck, and nail depth and deck movement may contribute. The 10-year workmanship warranty may cover installation defects, but the manufacturer's 30-year warranty may be denied because ventilation and deck requirements were not met. Responsibility may be shared among the original installer, the HVAC work, and the homeowner's lack of maintenance.
2. What code and manufacturer requirements apply, and what repair scope do you propose?
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Applicable requirements include the manufacturer's written instructions, which call for at least 1 square foot of net free ventilation per 150 square feet of attic floor area, and the building code's ventilation and exhaust provisions. Bathroom exhaust must discharge outdoors, not into the attic. The code also requires an ice barrier at the eaves in areas subject to ice damming; if the local jurisdiction adopted that requirement, the missing ice barrier is a code deficiency.
The repair scope should include: route both fans to the exterior with insulated duct, add ridge and soffit vents, install baffles to keep insulation away from the eave vents, correct any damaged sheathing or shingles, and add ice barrier at the eaves if required. Because these are code and ventilation upgrades, they should be presented as a separate change order, not as warranty work.
3. How should you communicate and document to protect the warranty position?
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Send a written inspection report with photos, attic temperature and moisture readings, ventilation calculations, and the manufacturer's installation instructions. Separate the findings into three categories: workmanship issues under your warranty, code-required upgrades, and homeowner/HVAC issues. State what the firm will repair under warranty and what is a chargeable upgrade.
Do not admit that the shingles failed or promise a full replacement before the manufacturer inspects. Invite the manufacturer's representative to inspect if a warranty claim is made. Keep a record of the homeowner's reports and your responses. Offering a clear, documented repair plan protects the firm's position and gives the homeowner a practical path forward.