There's a scupper on the side of the garage roof that drains that roof to the side yard. You can't see it in any photos. The main roof all slopes to a central roof drain that travels vertically through a chase in the middle of the house. It is well insulated to dampen the sound during heavy rains. It connects to the main weeping system at the foundation level.

Speaking of the roof. I was wondering if this flat roof used an engineered truss or is it preformed poly insulation? I am assuming it is EPDM covered. I am in Minnesota, so similar weather and an owner that wants to build a modern flat roof, and have been given a couple of those options, but not sure whether one is better.

The roof is 14" open web wood joists with open-cell spray foam insulation R50 sprayed to the underside of the plwood sheathing above. There's no air space and the spray foam doesn't require ventilation. It also forms the vapor barrier. The 2% slope is also built right into the roof joists so you don't need purlins. The membrane itself is a 2-ply modified bitumen membrane. You can use batt insulation instead but then you'll need deeper jousts to get sufficient air space above as well as vents on the top and sides.

Chris, a question on the slope. Since the roof needs to shed the water, is the entire slope to one side, is it split and then slopes to one side? I am working with a builder and am curious of how you did this. I would rather take your approach vs having preformed foam.

The garage all slopes one direction off to the side and the water is shed away from the building with a scupper. The main roof is different. The entire roof joist system is constructed with a 2% slope that directs all the water to a central drain which moves through an interior chase. The joist company makes the joists so that every one is slightly different resulting in an overall slope. You can achieve the same thing with sloped rigid insulation that sits on top of the joists.