Building Code for a Chimney

Building Code for a Chimney

Every state and most communities have rigorous chimney building codes that have to be followed by all contractors working on new construction, installing fresh chimneys in an old house or repairing and renovating old chimneys. The code is intended to avoid dangers that can be worsened by substandard chimney construction and materials, particularly in places as well as fire hazards.


Chimney foundations encourage a great deal of weight. The foundation for the chimney has to be substantial enough to encourage both exterior bricks or masonry as well as the weight of the inside fireplace(s). Some states require steel rebar reinforcement of this foundation. Footings have to be at least 12 inches in thickness and extend six inches on all sides from the foundation wall.

Interior Construction

Chimneys must be assembled with fireproof masonry, which includes solid bricks bricks or concrete. Rebar must be used by builders and in the majority of countries new chimneys have to have flue liners. Contractors must properly grout the liner as well as the rebar cells. The rebar has to be connected with metal fixtures of a specific thickness and size to the brick.

Flue Cross-Section

Should have a minimum diameter or cross-section in proportion. In California, that ratio is 1/8th for flues, 1/10th for flues that are square and 1/12th of the fireplace area for around flues.


In California events are trivial. Even earthquakes that can be felt can result in harm to brick and masonry structures. Six different construction zones, designated A through F are classified by the state; three of them have chimney specifications for locations that are earthquake-prone. When there is a chimney damaged, it has to be demolished before a replacement could be constructed, and also the replacement must conform to the upgraded building code of the state.


To decrease fire danger from heat and embers created by recreational fires, either rebuilt or new chimneys must have a minimum clearance both within and without the home. There is a minimal airspace of two inches demanded between interior and masonry partitions in California, which reduces to 1 inch for chimneys in exterior walls. On the outside, chimneys must extend at least two feet above any area of the building that lies above the roofing section that is neighborhood, and three feet inside ten feet.

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