Flat roof without parapet

So, for a parapet-enclosed shed roof with a slope of ten degrees or more, I would even consider a rejection appropriate. I do not consider the parapet essential, but the "rather symbolic" slope certainly is. Neither an ("gable-sided" but slight) overhang nor classic rain gutters do I consider "harmful" in terms of achieving the goal of visually fulfilling a "flat roof."

Perhaps you have already read my general mantra here: generally do not force a contractor to use techniques, constructions, or materials that they are not proficient in. This naturally applies particularly to flat roofs.

In the so-called flat roof guideline, it is stated that a flat roof should be designed with a slope of at least 5° to ensure reliable drainage of rainwater. An upper limit is not specified. Maybe this helps.