A chimney inside the house must have at least 2" (50mm) of clearance to the combustible structure. A chimney outside the house must have at least 1" (25mm) clearance to the combustible structure. Firestops must be installed in the spaces where the chimney passes through floors and/or ceiling (Figure 8).
A chimney must be the required height above the roof or other obstruction for safety and proper draft operation. The chimney must be a minimum of 3' (914mm) higher than the highest point where it passes through the roof, and at least 2' (610mm) higher than the highest part of the roof or structure that is within 10' (3048mm) of the chimney, mea- sured horizontally (Figure 10).
Minimum 1” Clearance for Exterior Chimney to Sheathing
FIGURE 8
Remember that insulation must not contact the chimney. There must be air space around the chimney. Insulation must be 2" (50mm) or more from the chimney (Figure 9).
FIGURE 10
Noncombustible
Material
FIGURE 9
9
