Roofing Moisture Intrusion Diagnosis
A contractor completed a low-slope roof (1/4:12) on a commercial building using a single-ply EPDM membrane over a new lightweight concrete deck. Within a year, the building owner reports water stains on the ceiling inside, particularly near the perimeter. The contractor inspects and finds: 1) ponding water in several areas, 2) some seams appear to be lifting, 3) no visible tears. The roof area is 10,000 sq ft. The contractor must determine the cause and remedy the issue without replacing the entire roof. The warranty is still active.
1. What are the likely causes of the leaks, and what diagnostic steps should the contractor take?
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Likely causes: 1) Ponding water due to inadequate slope or deflection of the lightweight concrete deck; ponding can lead to membrane deterioration and seam failure. 2) Seam failures from improper application (e.g., insufficient pressure, contamination) or from ponding stress. 3) Perimeter issues: insufficient termination or flashing details. Diagnostic steps: 1) Conduct a visual inspection of the entire roof, focusing on seams, flashings, and ponding areas. 2) Use infrared thermography to detect wet insulation. 3) Perform a water test (flood test) in suspect areas. 4) Check seam integrity with a seam probe. 5) Review installation records and material warranties. 6) Verify deck slope and deflection; if ponding is due to structural deflection, that is a design issue.
2. What repair methods should the contractor use, and how can they prevent recurrence?
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Repairs: 1) For ponding, add tapered insulation or crickets to improve drainage; ensure drains are clear. 2) For seam failures, clean and re-seal seams with splice adhesive or seam tape per manufacturer instructions. 3) Replace wet insulation if detected. 4) Repair flashings as needed. Prevention: 1) Ensure positive drainage (slope minimum 1/4:12). 2) Install additional drains if necessary. 3) Use proper seam application techniques and inspect seams. 4) Consider a maintenance program. Since warranty is active, coordinate with manufacturer to avoid voiding. Document all repairs.