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LIGHTWEIGHT BLOCK-IN SPECIFICATIONS (Continued)
Factory-Built Chimney (Continued)
The 3-Foot, 2-Foot, 10-Foot Rule (Continued)
Minimum Chimney Height on a Flat Roof
These minimum chimney heights are required by building codes for safety purposes, to allow
time for sparks exiting a chimney to cool before they land on the roof. In some problematic
situations, additional chimney height above the specified minimums may be necessary to
reduce wind-induced down drafting and back puffing, or to increase draft, thereby improving
fireplace operating characteristics.
Depending on the manufacturer and where the chimney is to be installed, special supports,
roof assemblies, radiation shields, or locking bands may be supplied as a part of the chimney
system. The manufacturer's installation instructions, which are reviewed by the listing
agency, specifies when and where each of these components must be used. Follow the
manufacturer's instructions for the use of flashing and an adjustable storm collar at the roof
line to prevent water from entering the house. Manufacturers require that chimneys
extending beyond a certain height above the roof (frequently above 5 feet) must also be
braced.
A chimney cap keeps out rain, birds and other animals, and may reduce down drafts. Spark
arresters, wire mesh devices designed to catch sparks and burning particles emitted with the
smoke, may be included with factory-built chimney caps. These spark arresters may become
encrusted with creosote, blocking the proper flow of flue gases out of the chimney. When
burning wood, it is recommended that the spark arrester be cleaned regularly, or removed
entirely unless individual conditions or local codes require their use.
10' or Greater
Wall or
Parapet
36"
6"
Page 23
Less
Than 10'
24"
42"
18"
"A"
"B"
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