Ponding, Seam Lift, and Interior Stains on a TPO Roof
At an 18,000 sq ft two-story office building, you inspect a 60-mil mechanically attached TPO roof installed in 2017. The last rain ended 36 hours before your 8 a.m. inspection. You observe standing water about 1.5 in deep in two areas totaling roughly 600 sq ft near the north drains. One drain strainer is clogged with leaves; the other drain is clear. Along the north parapet, several TPO seams have lifted about 1/2 in and show dark contamination under the edge. Inside, ceiling tiles in suite 210 are stained and one tile is sagging. The building owner says the roof "passed inspection" when installed and has a 15-year membrane warranty. No roof drawings or maintenance records are available. The buyer is a prospective purchaser and asks whether the roof needs replacement.
1. How should you evaluate and report the ponding?
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Separate the two ponding areas and consider both drainage maintenance and roof structure. Standing water 1.5 in deep 36 hours after rain is significant; many roofing standards and manufacturers treat ponding that persists beyond 48 hours as a concern, and 600 sq ft is not a small isolated depression. Start with the obvious: one strainer is clogged, which can explain ponding near that drain. The second area is more informative because its drain is clear, suggesting inadequate slope, a local deflection, or a membrane depression. Report the measured depth, approximate area, time since rainfall, drain condition, and whether the ponding appears to be against seams or at penetrations. Do not declare structural failure or roof replacement from visual evidence alone. Recommend clearing drains immediately and observing whether water dissipates; if ponding persists at the clear drain, recommend evaluation of roof slope and framing deflection by a qualified roofer and, if structural movement is suspected, a structural engineer.
2. How should you evaluate the lifted seams and the stained ceiling tiles?
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Treat the lifted seams and interior stains as separate findings until a moisture path is established. A 1/2 in seam lift with dark contamination under the edge indicates a workmanship or adhesion problem, not normal weathering on a roof installed in 2017. It may be covered by the membrane warranty, but warranty coverage is a contract question, not an inspection conclusion. The stained and sagging ceiling tile confirms moisture intrusion at some point, but it does not prove the roof is the source; condensate drains, HVAC units, plumbing, windows, and parapet flashing are alternatives. Report the seam condition with locations and measurements, report the interior staining with the caveat that the source is not determined, and recommend a roofer evaluate the seams and a moisture survey if the buyer needs to quantify wet insulation. Avoid telling the buyer the roof needs replacement; the evidence supports "repair and further evaluation," not a replacement verdict.
3. What recommendations and limitations belong in the report?
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Recommend immediate drain cleaning, a roofer's evaluation of all seams and parapet terminations, and a moisture survey if the buyer needs to know whether insulation is wet. Recommend that the seller provide installation records, warranty terms, and maintenance history. Because the roof is only a few years old, the buyer should also verify whether the warranty is transferable and whether ponding or seam defects are excluded. Limitations should state that the inspection was visual and non-invasive, that no roof drawings or infrared survey were available, that ponding was observed at one point in time, and that the interior stain source was not determined. The report should not promise that the roof will remain watertight or that the warranty will pay for repairs. The buyer's question about replacement should be answered by explaining what evidence would justify repair versus replacement, not by guessing.