TPO Ponding and Seam Separation on a 2014 Warehouse

Ponding is a drainage problem, not a membrane defect. The membrane is doing its job by holding water; the question is why water is there. At 1.5 inches deep and still present at 72 hours, the ponding exceeds the 48-hour threshold most manufacturers use, and it accelerates seam stress and insulation saturation. I would need the as-built taper plan, drain and scupper elevations, a slope survey, and the structural framing design. A 40-by-50-foot depression could come from a taper layout error, a drain set too high, insulation compression, or deck deflection under dead load. I would check the drain strainer and whether the drain is at the low point. Without that information I would not call it a material defect. The ponding is relevant to the warranty because manufacturers commonly exclude ponding and inadequate slope, but it is also relevant to the wind claim because standing water adds load and can affect seam behavior.

The 1/4-inch unbonded edge on every separated seam is the critical finding. A properly welded 60-mil TPO seam should be bonded across its full width; an unbonded edge is an installation or workmanship defect, and it gives wind a starting point to peel the seam. I would probe all seams, not just the 12, and document probe results, weld width, and any contamination or trapped moisture. I would also check perimeter edge metal and securement at the east parapet, since corner and edge zones see the highest uplift. The 60-mph event may have been the trigger, but the seams were already vulnerable. To separate the causes, I would look for peel versus tensile failure, elongation, and whether the membrane pulled fasteners or the seam opened. A seam that peels from an unbonded edge is a workmanship failure; a seam that tears in the field with a fully bonded weld is more likely wind overload. Both should be reported, because the repair and warranty positions differ.

The repair scope should address both the water and the wind damage. First, correct drainage: add or lower drains, revise the taper in Bay 4, or add a secondary drain so water does not stand. Second, repair every deficient seam with properly welded patches or seam plates, not just the 12 that separated, because the probe found a systemic unbonded edge. Third, replace any wet insulation and check the deck for corrosion. Fourth, restore perimeter securement and edge metal where the wind exposed a weakness. The warranty claim should be submitted with the probe data, the as-built taper information, and the ponding measurements. The manufacturer may cover a membrane defect, but it will likely exclude ponding and workmanship, so the owner should not expect a full replacement on the warranty alone. As the inspector, I would separate the ponding cause from the seam cause and give the owner a prioritized scope rather than endorse a blanket replacement demand.