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.
The Latin cross: nave, aisles, transept, apse
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.
The Romanesque church inherited the basilica from Constantine’s Rome and articulated it. The east end grew to house more altars and more clergy: a longer choir, apsidal chapels opening off the transept, and in pilgrimage churches an ambulatory with radiating chapels. The crossing became the point of emphasis, marked outside by a tower or lantern.
Orientation is nearly universal: the altar to the east, towards the rising sun and Jerusalem, the main entrance to the west.
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.
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
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
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.
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.
Cite this page Chris Paton, “The Latin cross: nave, aisles, transept, apse”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/rom-basilica-plan. Text, drawings and models licensed under CC BY-NC 4.0.