Figure 6.—Several extensions were necessary before this chimney would draw properly on account of the wind deflected from the nearby wall.
Figure 7.—A, A good foundation extending below the soil affected by frost. This chimney is well protected from ground moisture by the concrete carried above the surface; B, an insecure foundation. Supporting a chimney in this manner is a dangerous practice.
Supporting the Chimney
Stable foundations, preferably of concrete, should be provided, at least 6 inches wider all around than the chimney and 8 inches thick for one-story and 12 inches thick for two-story houses. When there is no basement or cellar ([fig. 7, A]), start the foundation of an exterior chimney well below the frost line; otherwise, extend the base to the same level as the bottom of the foundation of the building. Foundations for tall, heavy chimneys require special consideration.