This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Niches are of common occurrence in building work, especially in churches, halls, and other important structures. Sometimes they are simply recesses in the wall with straight corners and a square head, but more often they are semicircular in form, with spherical heads, in winch case the framing becomes a matter of some difficulty. The framing of the wall for a semicircular niche is the easiest part of the work, since all the pieces may be straight, but for the framing of the head the ribs must be bent or shaped to conform to the surface of a sphere.
Fig. 261 shows in plan the way in which the vertical studding of the walls must be placed. The inside edges must lie in a cylindrical surface, and will receive the lathing and plastering. There must be a curved sole piece for them to rest upon at the bottom and a cap at the top. The cap is shown at A B, in Fig. 262, which is an elevation of the cradling or framing for the niche. This figure shows how the ribs for the head of the niche must be bent. The ribs and vertical studs must be spaced not more than 12 inches apart, center to center.
The form of niches described above is the most common one for large niches intended to hold full size casts or other pieces of statuary, but smaller ones for holding busts and vases are quite common. These are often made in the form of a quarter sphere or some smaller segment of a sphere, with a flat base or floor and a spherical head, as is shown in section in Fig. 263. They are framed with curved ribs in the same way as described above, and finished with lathing and plastering.