INDEX TO ALL NINE SECTIONS
Where The Early Church Met
The Lack of Evidence For Early Formal Buildings
Constantine and The Construction of Churches
The Basilica and The Great Hypostyle Hall at Karnak
The Edict of Thessalonica
Where The Early Church Met
We are so accustomed to 'doing church' in buildings that have virtually no other function, that we forget that the ekklesia, or early church met almost exclusively in people's homes.
a) Day by day continuing with one mind in the temple, and breaking bread from house to house (Gr. oikia), they were taking their meals together with gladness and sincerity of heart, (Acts 2:46 NASB)
b) The churches of Asia greet you. Aquila and Prisca greet you heartily in the Lord, with the church that is in their house (Gr. oikia) (1 Corinthians 16:19 NASB)
c) Greet the brethren who are in Laodicea and also Nympha and the church that is in her house (Gr. oikia) . (Colossians 4:15 NASB)
d) and to Apphia our sister, and to Archippus our fellow soldier, and to the church in your house (Gr. oikia) (Philemon 1:2 NASB)
The Greek word oikia definitely means residence as made clear in
"I say to you, get up, pick up your pallet and go home (Gr. oikia)." (Mark 2:11 NASB)
They *came to the house (Gr. oikia) of the synagogue official; and He saw a commotion, and people loudly weeping and wailing. (Mark 5:38 NASB)
However, this does not necessarily mean that congregations were limited to a handful of people. Acts 1:4-15 tells us that about one hundred and twenty people were gathered together to devote themselves to prayer which means there was a building large enough to accommodate so many. Note it is very unlikely as some believe that the disciples met in an 'upper room' in the temple itself. See Footnote I
Besides which, Aquila and Prisca were tent makers and probably had a decent income. Philemon who was wealthy enough to own a slave also hosted a church in his home. Gaius, obviously a man of some means played host to Paul and to the whole church (Romans 16:23 NASB) and was commended by John for his hospitality especially to itinerant evangelists, (3 John:1:1, 5-7).
As the Lord added to their numbers, the church grew - not by by constructing another building nor by adding more people to the group, but by multiplying sideways. A single group divided itself into other groups, much like an organic cell makes a copy of itself and then splits into two new cells that, in turn, split into four new cells.
The Lack of Evidence For Early Formal Buildings
Also there is a distinct lack of evidence for formal public church buildings before the Roman Emperor Constantine (306 to 337 AD), made public Christian worship legal.
The Khan Academy, a not-for-profit educational organization, has a very interesting article on their site that describes how Christianity was radically transformed by Constantine. Although the article is almost exclusively confined to Constantine's influence on the architecture of the period, it tells us much about the earliest church. The quote below (Emphasis Added) refers to the earliest identified Christian church in Dura-Europos, Syria that dates back to 235 AD. (Emphasis Added)
".... there was not much that distinguished the Christian churches from typical domestic architecture. A striking example of this is presented by a Christian community house, from the Syrian town of Dura-Europos. Here a typical home has been adapted to the needs of the congregation. A wall was taken down to combine two rooms: this was undoubtedly the room for services. It is significant that the most elaborate aspect of the house is the room designed as a baptistry. This reflects the importance of the sacrament of Baptism to initiate new members into the mysteries of the faith. Otherwise this building would not stand out from the other houses. This domestic architecture obviously would not meet the needs of Constantine's architects. 
The fact that a wall was taken down to accommodate people indicates that the building was not designed as a 'church'. Dura-Europos was conquered by the Parthians under whose rule it it became an important provincial administrative center. The Romans captured Dura-Europos in 165 AD and greatly enlarged it as their easternmost stronghold in Mesopotamia. Thus it is extremely likely that some wealthy people had very large homes in the city.
Some point to the ancient Megiddo church discovered in the grounds of the Megidddo prison in Israel, that dates back to the 3rd century AD and is believed to be the oldest remains of a formal church in the Holy Land. However, anthropologist Joe Zias, former curator for the Israeli Antiquities Authority, disagrees. His statement ...
"My gut feeling is that we are looking at a Roman building that may have been converted to a church at a later date."
... is partially based on an inscription in the church which mentions Gaianus, a Roman officer, who donated "his own money" to have a mosaic made. The inscription says Gaianus, "having sought honor, from his own money, has made the mosaic." As Joe Zias says
"If I were a Roman soldier in the third century, I certainly wouldn't want my name on (the church).… This would not have been a good career move. In fact, it sounds like the kiss of death.” 
How then did "church" began to be associated with large buildings in which Christians assembled on a regular basis?
Constantine and The Construction of Churches
Constantine and the Roman Pietas
The Roman Emperors had a long history of constructing temples throughout the empire as a testament to Pietas considered to be a primary virtue.
Pietas, from which we get our English word "piety", was variously translated as duty, religious behavior, loyalty, devotion, or filial piety. In fact, "the Romans sometimes attributed their misfortunes, individual or national, to lack of pietas". Therefore, many altars and temples, that had been wrecked during the civil war following Julius Caesar's assassination, were rebuilt during the Pax Romana (a long period of relative peace and minimal expansion by military force), in 44 B.C. 
(As an aside, Michelangelo's sculpture of the body of Jesus on the lap of his mother Mary after the Crucifixion, is called The Pietà. It is housed in St. Peter's Basilica in Vatican City).
Therefore it is not at all surprising that Constantine wanted to construct 'temples' to his new found faith - something he set about with gusto building elaborate and imposing structures through out his empire beginning in the newly constructed capital of Constantinople. Some of the churches Constantine built were St. Peter's in Rome, the Church of the Nativity in Bethlehem, and the Church of the Holy Sepulcher in the Old City of Jerusalem etc. I believe there were nine in all.
Because the architectural style of the Roman temples were considered unsuitable, Constantine eventually decided on the architectural style of the Basilica that had been used by the Romans for centuries.
The Roman basilicas had no known religious function but were multi-purpose public buildings used for commerce, a meeting place for the citizens, and as a court. They were usually large rectangular halls, consisting of a wide central aisle called the nave. Rows of pillars separated the nave from aisles on either side, which had high widows to let light in. The nave, or main aisle, usually ended in a semi-circular room called an apse, opposite the main door. As a law court, the magistrate would sit in the apse, usually on a slightly raised dais. The apse was also used as as audience halls by the emperors and governors.
The Photograph On The Right is of The Basilica of Constantine in Trier, Germany (also known as the Cathedral of Saint Peter) is the oldest cathedral in the country, dating back to to 340 AD. It is believed to have been built under Helen's direction, and is still used as a Catholic church today. Note the semi circular apse at the far end
The Basilica Ulpia,perhaps the most famous of the Roman basilicas, was the largest, most lavish, and much admired basilica in Rome. It was named after Roman emperor Trajan and probably completed in A.D. 112. The Catholic Encyclopedia says (All Emphasis Added)
In the basilica, when used as a place of Christian worship, dating from the fourth century, the whole congregation of the faithful could meet and participate in the ceremonies and devotions. The bishop took the place occupied of old by the prætor or quæster; the presbyters, the places of the assessors. Very little change was needed to erect a Christian altar on the spot in front of the apse, where the heathen had poured out their libations at the commencement and conclusion of all important business. The basilica of the heathen became the ecclesia, or place of assembly, of the early Christian community. 
What is unfortunate is that although the architecture of the Roman temples was rejected because of its pagan associations, the design and layout of the basilica was not an original Roman idea but adopted from...
The Great Hypostyle Hall at Karnak
The many rows of columns separating the side aisles (a traditional feature of basilicas), can be traced back to Egyptian Hypostyle Halls. Hypostyle was an ancient Greek term that described a building with rows of columns supporting its roof. In fact, the Basilica Ulpia is very similar to one of the most famous hypostyle halls... The Great Hypostyle Hall at Karnak.
The Egyptians believed that their temples were the actual dwelling places of the gods - Karnak being home to the god Amun-Re. As said by the web site of The Karnak Great Hypostyle Hall Project ...
In antiquity, Karnak was the largest religious sanctuary in Egypt's imperial capital of Thebes (modern Luxor) and was home to the god Amun-Re, king of the Egyptian pantheon. For over 2000 years, successive pharaohs rebuilt and expanded the temples of Karnak, making it the largest complex of religious monuments from the ancient world. 
They describe the Hypostyle Hall at Karnak thus...
Covering an area large enough to accommodate the whole of Paris' Notre Dame Cathedral, the size and splendor of the Great Hypostyle Hall is enough to astound even the most jaded observer. The central nave is supported by twelve huge columns which are 21 meters (70 ft) high... These columns support a system of architraves and huge windows with massive stone grilles reaching a total height of around 20 meters (70 ft), similar to that of a Medieval cathedral. Flanking the nave are a further 122 columns, 12 meters (40 ft) high with closed-bud papyrus capitals. 
In other words, the Christian basilica was built in the style of the temple of the Egyptian God Amun-Re.
And yes, I do understand that architecture is strictly a matter of windows, doors, bricks, roof styles, columns etc. but we are supposed to be a group of people called to be separate from the world around us. Yet we have wasted time, resources, and enormous fortunes doing exactly what every heathen culture in the world does - build religious monuments, one more grand then the next.
In complete contrast whatever money members of the early church had was not wasted on extravagant buildings, but as the book of Acts tells us "not one of them claimed that anything belonging to him was his own, but all things were common property to them" (Acts 4:32) and that they actually sold their property and possessions sharing the proceeds with those that had need. (Acts 2:44-45)
However this is far from the end of the story.
The Edict of Thessalonica
Some 40 years after Constantine died in 337, Theodosius the Great became the last emperor to rule over both the eastern and the western halves of the Roman Empire. In a vigorous effort to do away with paganism in 325 A.D he convened what we know as the First Council of Nicaea to establish the universal norm for Christian orthodoxy. Unfortunately the proceedings were very influenced by three theologians from the province of Cappadocia. All three were mystics (two of them pioneered the rules of monastic life) and were formally trained in Greek philosophy which they introduced into Christianity and which have been accepted as a standard of orthodoxy ever since. DETAILS
After the empire split Gratian (Theodosius' counterpart in the west) took steps toward legal persecution of heretics. This was followed soon after by the jointly issued Edict of Thessalonica, delivered on 27 February 380 by Theodosius I, Gratian, and his half brother Valentinian II.
Emperors Gratian, Valentinian And Theodosius Augusti. Edict To The People Of Constantinople.
It is our desire that all the various nations which are subject to our Clemency and Moderation, should continue to profess that religion which was delivered to the Romans by the divine Apostle Peter, as it has been preserved by faithful tradition, and which is now professed by the Pontiff Damasus and by Peter, Bishop of Alexandria, a man of apostolic holiness. According to the apostolic teaching and the doctrine of the Gospel, let us believe in the one deity of the Father, the Son and the Holy Spirit, in equal majesty and in a holy Trinity. We authorize the followers of this law to assume the title of Catholic Christians;
but as for the others, since, in our judgment they are foolish madmen, we decree that they shall be branded with the ignominious name of heretics, and shall not presume to give to their conventicles the name of churches. They will suffer in the first place the chastisement of the divine condemnation and in the second the punishment of our authority which in accordance with the will of Heaven we shall decide to inflict. Given In Thessalonica On The Third Day From The Calends Of March, During The Fifth Consulate Of Gratian Augustus And First Of Theodosius Augustus. —Codex Theodosianus, xvi.1.2
The edict was significant for many reasons. Although the Doctrine of the Trinity was a central focus of this edict it was a joint effort by both Eastern and Western Roman Emperors to establish Nicene Christianity as the official state church of the Roman Empire. Only those who believed in the consubstantiality of God the Father, Son, and Holy Spirit were to be considered “Catholic Christians” - the first time this designation appears in a document.
What is of special interest is that, in the Edict of Thessalonica, 'heretics' were forbidden to give "their conventicles the name of churches". Note that Merriam-Webster defines the word conventicle as meaning an assembly for religious worship; especially a private meeting for worship not sanctioned by law. 
This edict, and others that followed, "established a pattern" of using the apparatus of the state to "suppress diversity of religious opinion". This would become "more pronounced as Theodosius' reign progressed".  Although the Edict of Thessalonica was largely aimed at the Arians, it did not take long for other "heretics" to run afoul of the emperors. As said by historian William Kenneth Boyd,
Theodosius made the violation of divine law equivalent to sacrilege, and such violation involved the loss of certain rights of Roman citizenship. First, the power of leaving or receiving legacies, one of the distinctive privileges of Roman citizens, was taken from the Manichaeans in 381, then from the Eunomians in 389. Honorious extended this legal disability to the Donatists and Pricillianists, while Theodosius the Younger applied it to all sects. The right to hold office at court or in the army was withdrawn from the Eunomians by Theodosius; Honorious excluded all enemies of the Catholic sect from service in the palace; and, finally, Theodosius the Younger forbade heretics to take the military oath of allegiance or to serve in the imperial army. 
The Jews were similarly affected. Honorious and Theodosius the Younger excluded them from military and all other public services except municipal offices". A law gave "temporal officials the right to inspect and increase the taxes paid into the public treasury by the Jewish communities" 
The Gospel of Christ was well on it's way to becoming something Christ never intended it to be and it certainly did not stop with the Roman edicts.
In England there were three acts of parliament passed (in 1593, 1664, and 1670) to coerce people to attend Church of England services. It called for imprisonment without bail of those over the age of sixteen who failed to attend church and to prohibit unofficial meeting of lay people. The Conventicle Act 1664 Punishment forbade conventicles of five or more people, other than an immediate family, meeting in religious assembly outside the auspices of the Church of England. The Conventicles Act 1670 included a monetary fine for anyone including preachers, who allowed their house to be used as a meeting place for any religious assembly other than the Church of England. 
Why all this history?
Simply because the events and edicts of the third and fourth centuries went a long way towards giving permanent form to Christianity as being a religion, the beliefs and practices of which were defined not by the Bible but by self professed leaders.
In summary, Constantine made Christianity the state religion and built a number of churches fashioned after the Roman Basilicas, that, in turn, were modeled on the Karnak Great Hypostyle Hall the largest religious sanctuary in Egypt's imperial capital of Thebes dedicated to the god Amun Ra.
A very few decades later another Roman emperor issued an edict forbidding "heretics" to call their "conventicles" churches. In other words, private meetings for religious worship was punishable by law.
However, a tremendously important question is why, according to the New Testament, should the 'called out' group of believers assemble together on a regular basis.
CONTINUE ON TO CHAPTER III: Why Did The Early Church Meet?
The two main reasons most Christians gather together for 'church' today are for corporate worship and to hear a sermon. In fact, the sermon, has so taken over center stage that the very meeting is judged by the quality of the message. Yet, neither by word or example does the New Testament ever give either of these as a reason for the church assembly. .
Much to the contrary, the New Testament is very clear - the assembly was to encourage and edify believers something that doesn't happen in most modern church meeting in which few people even know the names of very many of their fellow believers, much less what encouragement or help they may need.
Finally, there is not a single example in the NT that shows any church gathering was for the purpose of telling unbelievers the good news or getting people to join their "church". So why, according to the Scriptures, did believers gather together? HERE
Luke 24:53 says they were continually "in the temple" praising and blessing God; and some have supposed that the upper room here designated was one of the rooms in the temple. But there is no evidence of that nor is it very probable. Such a room as that here referred to was a part of every house, especially in Jerusalem; and the disciples probably selected one where they might be together, and yet so retired that they might be safe from the Jews. (Albert Barnes) [PLACE IN TEXT]
 Dr. Allen Farber. Early Christian Art & Architecture after Constantine.
 Greg Myre. Israeli Prisoners Dig Their Way to Early Christianity. The New York Times Company.
 Singapore Management University. Virgils Aeneas: The Roman Ideal of Pietas.
 Poole, Thomas. "Apse." The Catholic Encyclopedia. Vol. 1. New York: Robert Appleton Company, 1907. 8 Jan. 2014
 The Karnak Great Hypostyle Hall Project. Welcome to the Hypostyle Hall. http://www.memphis.edu/hypostyle/welcome.htm
 The Karnak Great Hypostyle Hall Project. Dimensions. http://www.memphis.edu/hypostyle/about.htm
 http://www.merriam-webster.com/dictionary/conventicle. Emphases Added
 Dan Graves, MSL. Theodosius Issued an Edict Church History Timeline.
 William Kenneth Boyd. The Ecclesiastical Edicts Of The Theodosian code, Paperback edition (2008) from BiblioBazaar. Pg. 51
 ibid Pg. 53