Introduction

THE octagonal plan in architecture conforms to the geometrical principles of the circular: it is introduced for purposes of contrast as well as for picturesque play of line in perspective. For small buildings, such as lodges and guard-rooms, garden temples, shelters for statuary and summer-houses the octagon has many advantages: when used for isolated buildings of large size with a diameter of from 40 to 60 feet, it can be arranged within a colonnade conforming to the inner shape, thereby introducing an interest which prevents a crude appearance. The octagonal plan cannot be successfully employed for isolated buildings with a greater diameter than about 60 feet: should the conditions demand a greater dimension, the figure should be changed into one with many facets, when it approximates closely to the circular or Pantheon type. A very large octagonal building would appear bald in effect in comparison with the reposeful character of a square or circular structure, and it is apparent that the need for interest in the wall surfaces of an octagonal building increases relatively to the size of the structure. The variety of treatment applicable to the octagon is expressed in the outline of the covering: pyramidal roofs and domical coverings preponderate in existing examples, but on a small scale, combinations of concave and convex or “tent” shapes may be introduced with good effect.

The octagonal plan on a large scale is best suited for the treatment of interiors where its extent can be viewed from a central point. In this connection the octagon has been very successfully adapted to rooms with coved and vaulted ceilings which of necessity have to be lit from the top.