A flat roof is never truly flat. It is built with a slight slope so water runs to the drains and leaves. When water instead sits in a spot for a day or more after the rain stops, that is ponding, and it points to a drainage or slope problem underneath. The causes are usually clogged or too-few drains, a low spot where the slope is inadequate, a deck that has sagged or settled, or debris damming the flow.
Ponding matters because standing water is hard on a roof. It works at the seams and the membrane, adds weight to the deck, and over time is a leading cause of flat roof leaks and premature failure. A coating or a new surface laid over the same low spots does not solve it, since the water will just pond again. The real fix addresses why the water is not leaving.
We correct ponding by fixing the drainage and slope as part of flat roof work and waterproofing, and where the membrane is sound, a reflective coating can follow once the water drains properly.
| Step | What to check |
|---|---|
| 1. Look after the rain | Water still standing a day or two after a storm is ponding. A brief puddle that drains is normal. |
| 2. Watch for dirt rings | Even when dry, old puddles leave rings of dirt or staining that mark where water pools. |
| 3. Check the drains | Slow, clogged, or too-few drains are a frequent cause. Clearing them is often the first step. |
| 4. Note any sag | A low spot may mean the deck has settled, which our sagging roof page covers. |
The order matters. First we get the water leaving the roof, by clearing or adding drains, correcting the slope, and addressing any settled deck that created the low spot. Only once the water drains properly does it make sense to repair the damaged seams and membrane and, where the roof is otherwise sound, add a reflective coating. Skipping the drainage step and just coating over the low spot means the water ponds again and the problem returns.
Left alone, ponding shortens the life of a flat roof and leads to leaks, which our page on delaying a repair covers. If the membrane is failing across the roof, a flat roof replacement that builds in proper slope is the honest fix. A roof inspection tells you which path fits your roof, and our page on the best flat roof material covers the options.
Not just a new surface over the same low spot. Request an estimate.
Call (310) 806-5959Tell us where water sits on your roof. We fix the drainage and give you a written price, with no obligation.