buttress, mass of masonry built against a wall to strengthen it.
It is especially necessary when a vault or an arch places a
heavy load or thrust on one part of a wall. In the case of a
wall carrying the uniform load of a floor or roof, it is more
economical to buttress it at certain intervals than to make the
entire wall thicker. Even when a wall carries no load, it is
usually buttressed rather than uniformly thickened. For a load-
bearing brick wall more than 8 ft (2 m) high a buttress is used
every 20 ft (6 m). The decorative possibilities of the buttress
were discovered in the ancient temples at Abu Shahrein in
Mesopotamia (3500–3000 B.C.), where they were used both as
utilitarian and decorative forms. The Romans employed
buttresses, which sometimes projected from the exteriors of the
walls and were then left as mere piles of masonry, without
architectural treatment. But in the large structures, such as
basilicas and baths, the buttresses that received the thrusts
from the main vaulting were confined to th