Is the roof slanted in the right direction? You are sending the water toward your house instead of away from it. This might create drainage problems in flash flood conditions.
There is already impervious coverage on the ground, sloped that way. This shed does nothing to change that, and it's not attached to the ground. If you really want to get away with this from a code standpoint, put wheels on it.
Also in the UK it's against regulation to have a wooden structure so close to a residential property... Although this is the US where most properties are made of wood... So probably no such rule?
Buildings that overlap are often seen as attempt to make an addition without the right permits. They have zero sense of humor about that over here either.
Since the wall of this building is actually under the roof line, they’ll make him tear this down or reroof his house to move it four inches over (although that might take a permit too, since you’re changing the roofline). Tearing it down is cheaper.
He may also be violating setbacks from the edge of the property, but those have been diluted here so frequently in large cities that he might be okay.
That is also the case in my area of the US. The wooden structure must be a certain distance from the house, fence, etc. However smaller structure don't need a permit so people just ignore the rules if space is tight. And some areas don't have strict enforcement of the building code particularly rural areas. But those properties tend to have lots of space.
Each member country of the UK have their own different planning regulations - Scotland, England, Wales and NI. Also please cite where having a shed next to your property is illegal in any one of these jurisdictions. Under certain dimensions and heights, planning "law" doesn't apply.
It looks like it’s designed to fit under of the eves of the house while still providing head room and there is a down pipe on the house that the shed can hook into sharing the soakway.