Acts 19:9 casts doubt on the notion that all first century congregations/churches were house ecclesiae. Here is Barnes' remarks on this verse:
"In the school of one Tyrannus. Who this Tyrannus was, is not known. It is probable that he was a Jew, who was engaged in this employment, and who might not be unfavourable to Christians. In his school, or in the room which he occupied for teaching, Paul instructed the people when he was driven from the synagogue. Christians at that time had no churches, and they were obliged to assemble in any place where it might be convenient to conduct public worship" (Barnes NT Notes).