U.S. Inspect Home Inspection:

Advisory Report

January, 2004

Technical Jargon: Chimney 2-3-10 Rule

“Technical Jargon” is a forum used to provide more information on terms commonly seen in U.S. Inspect reports.

The Chimney 2-3-10 Rule is the guideline for determining proper chimney height.

Improper or inadequate draw of the combustion exhaust gas can cause major safety problems for the home's occupants. Smoke and other exhaust gasses from the combustion of wood or fossil fuels contain carbon monoxide, carcinogens, and other harmful chemicals. The flue’s job is to carry these poisonous gasses out of the house. If the chimney is not tall enough, the flue can’t do its job, exhaust gasses are released into the house, and a hazardous condition is created.

Structures that are too close to the opening of the chimney flue can directly affect the way the flue “draws”, or exhausts the gases produced from combustion in the fireplace, stove, or other appliances. The solution to the problem? Extend the chimney to provide a minimum of 2 feet clearance to all roof surfaces and structures within 10 feet of the chimney and 3 feet above the highest point that the chimney penetrates the roof (i.e. the side of the chimney furthest up the roof slope). This is a national code, outlined in section FG503.5.4 of the International Fuel Gas Code.

Click here for more information about Chimneys.

Contributed by Justin Gore
Quality Assurance Supervisor
U.S. Inspect, LLC

Diagrams used under license from The Illustrated Home, © 1998 Carson Dunlop & Associated Ltd.