Water ponding on a new low-slope roof - any solutions?

Dear all, we just installed a new roof (modified bitumen with Dibiten Poly/4 APP, one ply with aluminum coating). We are located in San Francisco.

San Francisco recently start to rain and had a lot of fog (fog season now), and we noticed that the new roof has a water ponding area. See photo here:


My questions:

  1. Does this type of water ponding OK? As the water seems to sit there for a while now, and the surface area with water start to turn rusty color (not sure why). If the water continue to sit there for a while, could that potentially create some bigger problem (in SF we have fog all year round, and sometimes sun does not come out very often)?

  2. Usually how would a professional roofer handle/address this type of problem?


the easiest is to add an interior roof drain in the low spot.

Your question has been answered in 3 other forums already.

I suggest now, since you didn’t look up the answers, that you lay some sod over the water holding areas and apply for an Energy Stimulus Grant for a Green Roof.

Or, you can throw some fish food in the puddle and raise some Gold Fish.


You should change your name to Ed the answer man.

Lmao,at Ed’s suggestion…

Ed,what type of fish do you think are best for a situation like this? :smiley:

profesional here.

leave it the hell alone,
until someone complains about it, or
it leaks.


lol. Green Roofs for the win! :mrgreen:

that section looks like it was an internal gutter, or at least a level change.
Perhaps you can open the perimeter at one end and put a scupper in.
Or put a dropper in at the lowest point (if you can get into the ceiling space.)