Commercial Roofing
Standing water on a flat roof two days after the rain tells me three things before I climb the ladder: a drain is not draining, the deck has sagged into a bowl, or the insulation under that spot has gone soft. Each of them leads to a different repair, and the facility director in Edinburg, TX needs to know which one applies before spending anything. I begin with the edge of the puddle, mark where the water line stops, and measure how long it takes to clear.
Hanna's July 2020 visit brought street flooding to Edinburg, McAllen and Mission, and the Valley prepares for flooding all year. A roof that cannot shed a heavy rain quickly is carrying that load on the membrane and the structure.
Water that clears in a few hours is a different problem from water that lasts days. Long-standing ponds leave a visible ring of dirt and algae, a chalky film on the surface and, on some membranes, a swollen or softened sheet. I note the ring, measure its depth at the center and photograph it next to a fixed reference such as a curb or a drain. Heavier water also shows how the roof actually slopes, which a drawing may not.
Where ponds sit over a seam, the seam is the first suspect. Water under constant load finds the smallest opening and holds it open.
Heat adds its own wear to a pond. Between May and October the Rio Grande Valley is in its heat-safety season, and a shallow pool on a dark or aged surface cooks the sheet and the sealants around it day after day. I look for blistering, crazing and sealant that has turned chalky at the waterline, since those mark the area where the surface has already begun to give up.
Before I blame the slope, I check the outlet. Strainers packed with leaves, grit and roofing debris choke a drain badly, and a bowl that sits proud of the membrane never lets the last inch of water leave. I clear the strainer, pour water to watch the flow and check the line below when access allows. A drain or scupper that backs up on a clear day points to a blocked pipe, not a roof problem.
Scuppers through a parapet need the same test. A scupper set too high leaves a permanent pool behind it.
Flashing at a drain matters as much as the drain. The collar where the membrane meets the bowl is a frequent leak point, and water that stands against it wears it faster than a dry one. I check the clamping ring, the sealant and the membrane edge, and if the flashing is failing, it goes on the repair list with the pond.
Ponding becomes serious when it turns into trapped moisture. I map the area with an infrared moisture survey and confirm suspect spots with a probe or a small test cut. Wet insulation loses its value, adds weight and softens, so the roof deflects more under load and the pond grows. If the readings are dry beyond the pond, a surface repair and a drainage fix can solve the problem. If the readings run wide, the boundary of the work follows the moisture.
I record the readings on a photographed plan so a later inspection can compare them.
The survey is best done when the roof is cool, early in the morning or after sunset, because moisture shows up more clearly then. We also take readings at several dry reference points across the roof so the data has a baseline, which keeps a warm patch of dry insulation from being mistaken for a wet one.
The answer depends on the assembly. Tapered insulation or a crickets-and-saddles layout can re-form the slope toward a drain when the old roof tests dry and the framing can take the extra weight of the added layers. A new cover board and tapered insulation package is the common approach on a TPO roof that has aged but remains sound. If the deck itself is deflected, the correction may require structural attention before roofing material goes down, and I say so in the report.
Where the old roof has several layers, the count matters. A tapered package on top of two layers can leave the edges too high, force curb changes and add weight the deck was not meant to carry. I count the layers at a test cut, check the deck from below when I can and report the limits so the facility director knows what the structure will accept.
I extend the work from sound material on one side of the pond to sound material on the other, covering the seams, flashings and drains that sit in or beside it. That can include a new sump, a re-set drain bowl, a resealed lap and a membrane patch or section replacement. I photograph the existing layers before cutting and show the facility director the expanded boundary before proceeding if moisture runs farther than expected.
The written scope separates drainage work from surface repair, because the first usually has to happen even when the membrane is replaced.
A pond that sits over a seam is repaired from the sound sheet outward. The seam is cleaned and re-welded or re-bonded, the surrounding membrane is checked for hardening and the area is tested before the work closes. If the sheet has lost flexibility, a patch will not hold, and a section replacement is the repair that lasts.
Drain and insulation work involves material movement and sometimes interior access to the drain line. We coordinate with the site contact on hours, protected walkways and any room below the work area. For owners with several buildings, in Mission or McAllen for example, where the same storm brought street flooding, the photo record can be built in one format and compared across roofs. When ponding is just one symptom among several, I connect it with the building's seam condition, since the two tend to travel together.
The deciding factor is the membrane and the seams beneath the pond. Many sheets tolerate a day of water, but repeated or long-lasting ponds accelerate aging and push water into any small opening. Standing water that remains beyond a couple of days after rain should be inspected, and the depth and duration recorded.
Sometimes, if the low spot is near a feasible line and the structure allows the penetration. An added drain needs a flashed sump, a pipe route and a plan for overflow. Often tapered insulation is the simpler choice because it moves the water to a drain that already exists.
Some manufacturer terms limit coverage where water stands for a set period. The terms vary from one document to the next, so I read the paper before recommending the repair and record the pond depth and the time it takes to clear.
A moisture survey shows suspect areas, and a probe or small test cut confirms them. A soft feel underfoot, a roof that sags more than before and stains below the pond are signs as well, though only the survey and cut show how far the wet area runs.
Yes, with planning. Heat limits the working window and affects adhesives, so crews start early, protect cured work from direct sun and keep each opened area small. The schedule follows the forecast as well as the calendar.