Record where the water comes from and where it goes
Ask the roofing professional to map the wet areas against drains, scuppers, curbs and equipment. Record when the rain ended and whether the water persists or returns in dry weather. Condensate or other equipment runoff may explain a persistent wet area.
Manufacturer guidance uses specific definitions for ponding; it should not be turned into a universal countdown to roof failure. GAF identifies structural loading and biological growth among potential consequences of persistent water. Increasing water depth or visible structural movement warrants prompt professional attention.
Distinguish cleaning from a design correction
A blocked drain may need service. Water trapped behind equipment or in a depressed area may need a different correction. Ask the report to identify which explanation is supported and which needs plumbing or structural investigation.
Tapered insulation can create drainage slope, as Johns Manville’s product guidance explains. Whether it is suitable depends on the existing assembly, outlet locations, transitions and available heights. Adding drains or altering overflow arrangements requires coordinated design.
Review the entire discharge route
The assessment should follow water beyond the membrane to the drainage outlet and downstream system. Ask whether the roof outlet itself, connected piping or site discharge needs attention. A clear roof drain does not prove the entire route works.
- Map the area and document observations without walking through standing water.
- Identify the intended primary and overflow drainage paths.
- Ask who will review plumbing capacity and structural concerns if they arise.
- Require a drawing of proposed changes and how surrounding roof details will connect.
Verify the outcome
Ask the contractor to state how drainage performance will be reviewed after the work, including follow-up observations after rainfall. Keep the before-and-after map; it is more useful than a closeout statement that the membrane has been replaced.