What minimum window size allows two courtyards to share one eruv?
The window must be at least 4×4 handbreadths (about 12×12 inches) and within 10 handbreadths of the floor to serve as a valid connection.
Question 2
Are adjacent rooftops of different homes considered separate domains?
Adjacent rooftops at roughly the same height are treated as a single domain — a practical leniency that reflects how interconnected dense neighborhoods actually are.
Question 3
A window between two courtyards is 15 handbreadths above the ground. Is it valid for eruv purposes?
The window must be within 10 handbreadths of the ground to serve as a meaningful connection between courtyards.
Question 4
Two courtyards share a wall. Who determines the wall's domain status?
Wall ownership depends on who built it, how thick it is, and architectural features. These factors determine which courtyard "owns" the wall for domain purposes.
Question 5
Can a closed window still serve as an eruv connection?
A valid window connection requires an actual opening or openable window. A permanently sealed wall — even where a window once was — doesn't qualify.