Flat Roof Drainage Question

[palikona]

I am currently doing a concept design for a two-story addition off the back of an existing two-story commercial building in a dense, urban neighborhood. The existing building and new addition are hemmed in on two sides by buildings and zoning has no side setbacks. The new addition in the back will be taller than the existing building, and the existing building's roof slopes @ 1/4"/foot towards an existing gutter that will be removed, where the new addition will interface with the old building. My question is about drainage of the lower existing roof: should I design in one or two new roof drains near the interface of the two buildings and run the line through the new addition, to daylight out into the parking lot. Are there code issues I should be aware of? Or would there be a better way to do this?
Thanks for the help!!

 

[my250r11]

Should check to see if there are any storm water regulations for your City or State. A lot of places do not allow your property to directly drain to the next lots, alley's or streets. Depends greatly on your location & AHJ.

 

[ICE]

The existing roof slopes to a gutter. A gutter is not a roof drain. You will now create a roof drain. Code will require a primaqry and a secondary roof drain. The roof shall slope to the roof drain. If the parking lot drains to the street the roof drains should be able to end there.