Roof Problems · For owners & managers
Ponding Water on Flat Roofs: Why It Happens and What Helps
Water that sits on a roof long after rain is called ponding. It adds weight and speeds up wear.
Common causes
Ponding has a few usual causes.
- Clogged drains
- Deck sag
- Crushed insulation
- Poor original slope
Why it matters
Standing water breaks down some membranes and coatings, hides punctures, and adds load to the structure.
Fixes
Clean drains first. Then consider added drains, crickets, or tapered insulation during repair or replacement.
Common questions
- How long is too long?
- A common rule of thumb is water still present 48 hours after rain.
- Do coatings fix ponding?
- Some tolerate it, but they do not remove the cause.