Order the church as a single path: a colonnaded atrium, a narthex, the long nave drawn toward the altar, and the apse framed by a triumphal arch at the end of the axis.
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The church turned to the east, like a ship
Build the house of assembly long, with its head toward the east and rooms for the clergy on either side of the east end; seat the bishop in the middle of the head with his presbyters about him, and the people in order down its length.
The compiler of the Apostolic Constitutions compares the church to a ship: the bishop is its captain, the deacons its sailors, the people its passengers, and the building is long so that it can carry them all toward the east, the direction of prayer and of the coming of Christ. It is the earliest text to prescribe the orientation of the building itself.
Practice took time to follow. Constantine’s great basilicas in Rome (the Lateran, St Peter’s) had their entrances at the east and their apses at the west, so that the celebrant faced east across the altar toward the people and the doors. The eastward apse became normal in the Greek East in the later fourth century, and in the West over the following centuries; by the Middle Ages it was universal.
Related rules
To turn a domed square into a long church, open two of its great arches into semidomes of the same radius, and open the semidomes in turn into smaller exedrae, so that the space expands by stages from the central dome.
Hagia Sophia: central square 31 m; two semidomes of radius ≈ 15.5 m; four exedrae; interior ≈ 31 × 70 m
Divide a square naos into nine bays: dome the central one on a drum over four columns, barrel-vault the four arms of the cross, and cover the four corner bays lower; add three apses to the east and a narthex to the west.
arms = central bay width; corners lower; dome on pendentives over four columns
Crown the four corner bays of a cross-in-square with smaller domes on drums around the great central dome, making a five-domed quincunx.
Make a basilica between a third and a half as broad as it is long; make each aisle a third of the width of the central space, and the columns as high as the aisles are broad.
W = ⅓ to ½ L; aisle = ⅓ nave; column height = aisle width; upper columns ¼ smaller
Lay out the church as an Early Christian basilica (a tall nave lit from above, lower aisles on either side, a sanctuary ending in an apse to the east) and cross it with a transept, so that the plan becomes a Latin cross with a tower over the crossing.
Cite this page Chris Paton, “The church turned to the east, like a ship”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/apostolic-church-east. Text, drawings and models licensed under CC BY-NC 4.0.