Hang on a cotton-picking minute! Surely the lofts of a row of terraced houses were never just one continuous space! Were they?
Surely the attic space above each house would have a brick partition walls, extending upwards to the roofline, to separate each attic from its neighbours, wouldn't it?
I mean, Curly's attic must be private, because he's got his observatory up there.
So it must just be the lower end of the street where the builders must have got fed-up when building the dividing walls. They just got up as far as bedroom height and said, "That'll do, let's go to The Rovers."
Or summat like that...