HOUSETOPS
The Jews used to have an upper room for their houses that they used as guest room or prayer room. The rooftops were flat. Hence, while Jesus was preaching at a crowded home in Capernaum, four people could lower a paralytic for healing.
The announcers and preachers used the flat rooftops also for public announcements and preaching. After Pentecost, Peter addressed a large crowd from the rooftop of Mark’s house where the disciples received the Holy Spirit in the upper room. The preachers of the ancient Church must have used the rooftops for preaching, especially when the Jews expelled them from the synagogues.