Chimney Construction Details
Because of its height and weight, a masonry chimney should be sup- ported by a suitable foundation. This foundation should extend at least 10 inches below the bottom of the chimney and a similar distance beyond its outer edge on all sides (see Figure 3-4). The foundation can be made more stable by making the base larger in area than the top. This can be accomplished by stepping down the footing at an angle.
Chimney Cap
The chimney cap (or capping) is both a decorative and functional method of finishing off the top of the chimney (see Figure 3-22). Built of brick, concrete, or concrete slab, the chimney capping tends to counteract eddy currents coming from a high roof. The slab-type
capping shown in Figure 3-23 is an effective means of preventing downdrafts. Chimney cappings are usually designed to harmonize with the architecture of the structure.