Bay

Rules that use the word

Every arch is first built on a frame. An arch cannot support itself until it is complete. Build it on a timber centring shaped to the intrados, strike the centring only when the keystone is set and the mortar has taken, and reuse it from bay to bay, which is one reason to keep the spans of an arcade equal.

Step the wall forward to the centre. Build up a façade in layers: let the wall advance in stages towards the central bay, double the pilasters or columns as it advances, and break the entablature forward over every support.

The pendentive: a sphere cut by a square. To set a round dome on a square bay, imagine a sphere passing through the four corners of the square; cut it by the four vertical planes of the sides and by the horizontal plane of their crowns. The four spherical triangles left in the corners are the pendentives; the circle at their top carries the dome.

The sail vault: one sphere, uncut. If the sphere that forms the pendentives is simply continued above the ring, the bay is covered by a single shallow dome, the sail vault or pendentive dome, which springs directly from the four corners.

The cross-in-square: nine bays. 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.

Five domes in a quincunx. 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.

Where it appears in the book

In the chapters Walls and Openings, Vaults, Domes, Proportion and Number, Frame and Skin, Columns in Company, The Classical World, Byzantium and the Early Church.

A feature of Chinese, Byzantine, Japanese, Russian, Romanesque, Tudor, Italian Renaissance garden, Georgian and Colonial, Victorian, Edwardian architecture.

Nearby in the glossary

Base · Basilica · Bastion · Batter · Bay window · Beaux-Arts · Bedding out · Bekleidung