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.
Apses in echelon
Multiply altars at the east end by opening apses off the transept arms and the choir, stepped back from the main apse in echelon, each with its own small semidome and roof.
Monastic communities needed many altars for the daily private masses of their priest-monks. The Benedictine or “echelon” plan answered by ranging apses side by side; the alternative, pioneered in the Loire valley around 1000, was the ambulatory with radiating chapels. Both give Romanesque east ends their clustered, stepped silhouette of half-cones and semidomes.
Related rules
End the choir in a semicircle of piers; wrap an aisle (the ambulatory) around it, and open a ring of chapels off the ambulatory, each with its own altar and windows, so that the east end steps down in tiers of roofs and buttresses.
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.
Let the square of the crossing set the measure of the whole church: the nave and transept arms are multiples of it, each nave bay is a square of the same size, and each aisle bay a square one quarter its area.
nave bay = crossing square; aisle bay = ¼ of it; nave length = n squares
Mark the west end with a massive, towered block containing an entrance hall below and a chapel or gallery above, rising higher than the nave: a church in front of the church.
Build the baptistery, and its font, with eight sides, because the eighth day, the day of the resurrection, is the day into which the baptised are born.
plan and font = octagon (8 = 7 + 1, the day after the Sabbath)
Cite this page Chris Paton, “Apses in echelon”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/rom-apses. Text, drawings and models licensed under CC BY-NC 4.0.