Niches with statues

In a bonded masonry wall the courses above an opening corbel over it of their own accord, so the lintel carries roughly the triangle of wall with sides rising at 60° from its ends; everything above that triangle arches onto the jambs.

load ≈ equilateral triangle on the span: W ≈ 0.43 · L² · t · ρ g

In a row of arches the thrusts of neighbouring arches cancel over each intermediate pier, which may therefore be slender; at the ends of the row nothing balances them, so the outermost piers must be made wider or buttressed.

Over a doorway or window spanned by a lintel, turn an arch in the wall above so that the weight of the masonry is carried round the opening onto the jambs, leaving the lintel to carry only the small triangle of wall beneath the arch.

Front a basilican church with two storeys of the order: the lower as wide as nave and chapels, the upper as wide as the nave alone, joined by scrolls and crowned by a pediment.

Il Gesù (reconstructed): lower ≈ 34 m wide, upper ≈ 20 m; scrolls fill the difference

Mark the main door by setting a segmental pediment inside a larger triangular one, or by breaking the pediment open to hold a cartouche or statue.

Divide the inside of a dome into coffers that shrink in step with the meridians as they rise, so that their perspective deepens the dome and draws the eye to the light of the lantern.