This section is from the book "A Treatise On Architecture And Building Construction Vol2: Masonry. Carpentry. Joinery", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
Niches. Vaulted, groined, and domed passages, such as those just described, seldom occur except in monumental work, and the side walls of such passages are often broken by niches for the reception of pieces of statuary, vases, etc. Fig. 89 shows the construction of such a niche. The plan (a) shows the base acb, composed of 1 1/4-inch plank; halved into the front edge of this base are the two studs a and b, shown in the elevation (b) at a' and b', extending from the base to the head piece k, to which they are nailed. The studs n, o, p, etc., extend from the base to the plate /, on which rests the curved ribs n', o', p', giving the head of the niche a semi-domical form; the front is closed by two quarter-circle ribs efg, let in and nailed to the studs a' and b'. Bridging, or stiffeners s, are inserted between the ribs, and the whole is then lathed with wire, or other metallic lath. The proportion of such a niche should be such that its height to e should be twice its width between a' and b'.