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.
257. When brick buildings have a parapet wall and flat roof, and the item of cost has to be considered, a brick cornice is generally the most satisfactory, provided one of terra cotta cannot be afforded; and is very much better than a galvanized-iron or wooden cornice, for besides being more durable, it does not, like them, require painting at frequent intervals.
Where any considerable amount of projection is required, it is best to adopt some corbel treatment, building the corbel up by slightly projecting each course. This mode of laying brick cornices is shown in Figs. 109 and 110.
258. Fig. 109 shows an arched and dentiled cornice, very effective in high buildings, where a good shadow effect is desired without great projection. The cornice is shown in elevation at (a) and in section at (b). At a are shown the 4-inch brick arches between the corbels, composed of brick laid the 4-inch way; for very special work, these brick should be gauged, or rubbed, so that they will fit exactly in the arch. At b are shown the brick corbels, made 8 inches, or one brick, wide, and seven courses of brick high, each course having a projection of slightly over 1/2 inch; c shows the belt course, of two courses of brick, on which the corbels stop, the upper course projecting 1/2 inch; and d is a dentil course of brick laid as headers, with a 4-inch space between each dentil, which is two courses in height, each course projecting 1/2 inch; e shows a galvanized-iron crown mold that can be used to form a gutter if desired.
259. Fig. 110 shows a less elaborate and cheaper brick cornice. The elevation is shown at (a) and the section at (b); the crown course a is composed of two courses of brick, each projecting 1/2 inch. The corbels b are each 4 inches or onehalf brick wide, and are spaced 4 inches apart; three of the courses in each corbel project about £ of an inch each, making the whole projection about 2 1/4 inches. At c is shown the belt course on which the corbels stop, laid in two courses of brick, the lower course having a projection of 1 1/4 inches, and the upper course setting back 1/2 inch from the face of the lower course. At d is shown the dentil course of brick set on edge, having a space between each dentil of 2 1/2 inches, or the thickness of a brick, and projecting 1 inch. The belt courses c should be protected on top from the weather by-sheet lead, as shown in Fig. 107, or by Portland cement, as shown in Fig. 108.
260. A very effective brick cornice, especially for buildings of medium height, is shown in Fig. 111. This cornice bonds well, gives a strong shadow, and is easily laid. At a is shown the two top courses of brickwork in the cornice; the bricks are laid up as stretchers, and the upper course projects 1/2 inch over the lower, and the lower course 1/2 inch over the dentil course. At b is shown the upper dentil course, projecting 1 1/2 inches over the lower dentil course; c is the lower dentil course projecting 2 inches beyond the lower belt course; d is the lower belt course of two courses of brick, each one projecting 1/2 an inch; and at e is shown the galvan-ized-iron ogee crown mold, which may also be used to form a gutter if desired.