Fix ponding on McKinney commercial roofs: measure the standing water, separate drain faults from low spots, then correct slope, outlets and damaged membrane.
Tell us about the building and what you are seeing. We reply with the next practical step.
A puddle that outlasts the rain is the first failure to measure. Depth, duration and distance from the nearest drain tell us whether the cause is a blocked outlet, a low spot in the deck or a roof that was never sloped to shed water. In McKinney, TX, a quick storm can drop a lot of water on a flat roof, and the question is how fast the roof gets rid of it. We walk the roof the morning after rain, because that is when ponding shows and before the sun hides the evidence.
Dallas-Fort Worth normals list about 37 inches of precipitation a year, and May is the wettest month at close to 5 inches. Those numbers come from the regional station and say nothing about a particular roof, yet they explain why drainage review is a standing part of how we inspect.
We start by photographing every pond and measuring its depth and edge. A tape and a level are enough on a small roof. On a larger one, a laser or a string line shows how the surface relates to the drains. Then we trace each pond to its nearest outlet and note whether that outlet sits high, sits low or is blocked.
The pattern points to a cause. Ponds ringing a drain suggest a blocked or undersized outlet. Ponds in the middle of a bay suggest deck deflection or compressed insulation. Ponds along a wall suggest a parapet that traps water. Ponds near equipment suggest added load or a curb that dams the flow.
We also check what the water has done. Algae, silt rings, blistering, softened seams and granule loss all show where water has stood for long periods. Those spots go on the roof diagram with photographs, because they set the repair boundary.
Edges and flashings need the same walk. Water that stands against a wall base loads the flashing continuously, and a failed flashing at the edge of a pond is a direct path into the building. We probe the termination, check sealant and fasteners and mark any opening before the pond is drained for repair.
Equipment adds its own signs. A cooling unit with a leaking condensate line can create a pond that is not rain at all, and a roof that stays wet in summer weeks without rain is telling us something. We trace those sources before blaming the membrane.
Most ponding repairs start with the drain path. We clear each bowl, remove the strainer, test flow and look at the drain body for cracks and loose clamping rings. Where debris has built up, we clean it and photograph the bowl before and after. A drain and scupper service done before the spring storm window often removes the problem entirely.
Overflow routes get the same attention. A scupper that is blocked, set too high or missing leaves the roof without a safety valve. If the main drain clogs during a storm, the water rises until it finds a path, and that path is usually a wall flashing.
Access matters when the roof is wet. We schedule the first drain visit on a dry day, plan for a roof hatch or ladder that is safe in wet shoes and coordinate with the facility director if the work crosses an occupied shift. Drains are often above production areas, so a spill during cleaning has to be controlled.
Standing water ages a membrane faster than dry surface around it. Seams stay under pressure, algae grows, and heat cycles the sheet differently under water. Many manufacturers also limit warranty coverage where ponding persists, so the condition can affect paperwork.
Wet insulation is the larger risk. Water that enters a small opening travels sideways under the membrane and does not dry on its own. An infrared moisture survey shows the wet areas as a map, and cores prove what the scan suggests. Wet insulation loses its thermal value, adds weight and can corrode the deck.
The repair boundary follows the moisture, not the pond. If the insulation is wet beyond the visible puddle, the removal extends past it. If a seam under the pond has opened, it is repaired inside the same boundary, as with any seam failure. We mark the limits on the roof before any cutting begins.
Surface wear counts as well. Granule loss on a bituminous roof, chalking on a single-ply sheet and softened coating under a pond each show how long the water has stood there. We scrape, probe and photograph, then compare the pond area with a dry area nearby, so the difference shows in the photographs.
The fix follows the cause. A blocked drain is cleaned and put on a service schedule. A drain set too high is lowered or a sump is formed around it. A roof that needs more outlets gets new drains, with plumbing coordinated by the building engineer. A deflected deck is documented and sent to a structural engineer before anything heavy is added.
Tapered insulation is the usual permanent answer when the surface itself is flat. It adds slope by varying thickness and directs water to the outlets. It is installed most efficiently as part of a recover or replacement, when the membrane is already being renewed. Our insulation and cover board choices set both slope and surface strength.
A coating alone does not cure ponding. It may seal the surface under the pond, but the water stays. If the owner wants a coating for other reasons, drainage is corrected first, and we say so in writing.
Drainage work depends on dry weather. Taper, sumps and membrane need clean, dry surfaces, and a spring storm can undo a half-finished area. We schedule the larger corrections for a stretch with a stable forecast and stage temporary drain protection so debris does not enter the new work.
Heat plays a role too. In July and August a hot roof can flash-dry adhesives before they bond. Crews start early and finish adhered sections before the afternoon peak.
On a site along US 75, SH 121 or the US 380 retail districts, the work often has to fit around tenants and deliveries. We agree on a staging area and lift plan, and we report to the facility director at the end of each day.
After the correction, we map the roof again and record how water behaves after the next rain. The owner receives the diagram, photographs, drain service log and the next inspection date. A return visit confirms that the ponds are gone or reduced to a harmless film.
Owners with several roofs can include drain checks in a multi-site roof program. Buildings in Plano or Melissa can follow the same schedule.
Tell us which areas hold water, your operating hours and the roof access route. We will measure the ponding and sequence the correction around your workday.
Short answers to what owners and facility managers ask before a roof visit.
Water that remains a day or two after rain is a warning. Water that remains for days is a defect. Measure the depth and the duration, and we will classify the condition.
No. A coating protects the surface. It does not change the slope. Correct drainage first, then consider a coating if the membrane is sound.
Often, if the structure and plumbing allow it. A new drain needs a pipe route, a sump and flashing. We coordinate with the building engineer. In some cases a scupper through the parapet is simpler.
That is a structural question. We document the deflection and recommend an engineer before adding insulation or membrane.
Not always. If the existing layers are dry and attached, a recover with taper can add slope. If they are wet, the old layers come out first.
Send a question about the building and we will reply. Or call 555-555-5555.
