Leave an opening in the atrium roof not less than a quarter nor more than a third of the atrium’s width, with a length in proportion; beneath it set a basin to receive the rain.
compluvium width = ¼ to ⅓ W
The compluvium lit and ventilated the atrium and collected rainwater, which ran down the inward-sloping roof into the impluvium, a shallow marble basin in the floor, and from there into a cistern. The opening had to be large enough to light the room and small enough to shelter it.
The atrium with its patch of sky and its pool is the Roman house’s centre of gravity, a courtyard turned into a room. It anticipates the cloister, the patio and the light-well of later architecture.
Raise the central nave above the lean-to roofs of the aisles and pierce the upper walls with a row of windows, the clerestory, so that the middle of a wide hall is lit from high on both sides.
nave height ≈ 1½–2 × nave width; one window over each bay of the arcade
Edge the beds before the portico with box, clip box into figures of animals set facing one another, and in the garden beyond cut it into many shapes, even into the letters of the owner’s name.
In a peripteral temple the flanks have twice as many intercolumniations as the front: six columns in front means eleven along each side, counting the corner columns twice.
side columns = 2n − 1 (Vitruvius) · 2n + 1 (Greek practice)
Divide the whole front of the cornice into nine parts; give one of them to the height of the tympanum, measured at its centre.
tympanum height = cornice width ⁄ 9 (≈ 12½°)
Do not leave a large circular building as a bare cylinder: steady it with features that break the curve and fix its axes: a portico, stairs, a projecting bay or a recess on the axis.
For a hall of assembly use the “D” or tribune plan, a half-circle closed by a straight side: it gives ample room to the audience, a central place to the speaker and scope for display in the architecture.
Cite this page Chris Paton, “The opening in the roof”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/compluvium-size. Text, drawings and models licensed under CC BY-NC 4.0.