The Chimney Sweep Online Fireplace, Woodstove, Gas Stove and Barbecue Shop
Chimneys that begin halfway up the wall and are supported by angle bracing to the wall studs are sometimes found in older houses. These have been outlawed by the code authority, for two good reasons:
1) Masonry won't flex, so the mortar joints and liner tiles weaken and crack when the supporting wall shifts as the house settles
2) Wall studs and supporting framing are made of combustible materials, which could eventually ignite from direct contact with the hot chimney surfaces
Note: there are no "grandfather clause" loopholes in the fire code. Pedestal chimneys cannot be used, even in existing installations.
Properly constructed masonry chimneys begin at ground level, and are supported by a poured concrete footing.
A 2" airspace is maintained between the chimney and the house structure, to allow the house to settle without stressing the chimney and to prevent heat transfer to the surrounding combustibles.
Manufactured metal chimneys are exempted from the ground-level support requirement, and are often used to replace existing pedestal chimneys to avoid the considerable expense of extending the masonry structure down through the floor.
|THE BOTTOM LINE: NEVER VENT INTO A PEDESTAL CHIMNEY!|
|Note: Each Code Authority chooses the standards that regulate appliance and chimney installation and usage in their jurisdiction,
and may modify code specs as desired. The above-referenced specification is from the Uniform Building Code, and may not
reflect the code requirements in your area. Contact your Code Authority for local regulations.|