Pedestal Chimneys

CODE VIOLATION:
PEDESTAL CHIMNEY

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.

CODE REQUIREMENT:
CHIMNEY STARTS AT FOUNDATION

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.