Low-Slope EPDM Roof With Ponding, Clogged Drain, and Parapet Seam Separation
An inspector is evaluating a 40-foot by 60-foot low-slope roof on a 30-year-old commercial building. The roof is covered with a 15-year-old EPDM membrane over polyisocyanurate insulation, with a stated slope of 1/8 inch per foot. Two roof drains and one scupper serve the roof. After 48 hours without rain, a 20-foot by 30-foot area of ponding remains about 2 inches deep near one drain. The drain strainer is clogged with leaves, and an 18-inch section of seam separation is visible at the parapet. The inspector also sees several blisters and loose termination-bar fasteners. The building owner wants to know whether the roof can be repaired or must be replaced.
1. Distinguish the likely causes of the ponding and seam separation. What can and cannot be concluded from a visual inspection?
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The ponding is likely influenced by the clogged drain strainer, which prevents water from leaving the roof, and possibly by insufficient slope, deck deflection, or settled insulation. The stated 1/8-inch-per-foot slope is minimal, and a 20-foot by 30-foot pond that remains 48 hours after rain is significant. The parapet seam separation is a membrane and termination issue, likely related to loose termination-bar fasteners and movement or adhesion loss at the edge; it is not necessarily caused by the ponding. A visual inspection cannot determine whether the insulation is saturated, whether the deck has deflected, or whether the drain leaders are restricted below the roof. The inspector should report the observations and limitations and recommend a roofing contractor and, if structural movement is suspected, a qualified structural professional.
2. What reporting and repair recommendations are appropriate?
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The inspector should report the ponding dimensions and depth, the clogged strainer, the separated seam, the blisters, and the loose termination-bar fasteners. The recommendation should include clearing the drains and scupper, repairing the seam and termination, and evaluating the roof for concealed moisture and insulation damage. Because the ponding is recurrent or persistent, the owner should also have the roof slope and drainage evaluated; if deck deflection is suspected, a structural evaluation is appropriate. The inspector should not declare that the entire roof must be replaced based only on this visual inspection, nor should the inspector guarantee that localized repairs will solve all ponding. The report should state that the membrane and insulation were not opened for inspection and that a roofing contractor should determine the repair scope.