The purpose of the building code is to establish the minimum requirements to provide a reasonable level of safety, public health and general welfare through structural strength, stability, sanitation, adequate light and ventilation, energy conservation, and safety to life and property from fire and other hazards attributed to the built environment and to provide a reasonable level of safety to fire fighters and emergency responders during emergency operations.

Building codes vary between different regions and not all the jurisdictions follow or adopt the International Code Council’s (ICC) codes. In most cases, many have the same restrictions. A summary of the typical codes relating to the venting of dryer exhaust to the home’s exterior are as follows:

• Dryer vent systems shall be independent of all other systems and shall convey the moisture to the outdoors.

• Terminations shall be a minimum of three feet from property line and 12" above the ground and not exhibit any type of screen.

• Vents and duct connections shall be connected mechanically (with sheet-metal screws or rivets) and shall not protrude more than 1/8" into vent.

• Exhaust vents shall be equipped with a back-draft damper and no screen.

• Vents shall be constructed of minimum 0.016-inch-thick (0.406 mm) rigid metal ducts, having smooth interior surfaces with joints running in the direction of air flow and having a minimum interior diameter of 4".

• Flexible duct shall not be concealed within the construction.

• The maximum length of a 4-inch (102 mm) diameter exhaust vent shall not exceed 35 feet (7620 mm) from the dryer location to wall or roof termination, and shall terminate with a full opening exhaust hood. A reduction in maximum length of 2.5 feet for each 45-degree bend and 5 feet for each 90-degree bend shall apply. Installations where this length is exceeded shall be installed in accordance with the manufacturer's installation instructions.

• The passageway of dryer exhaust duct terminals shall be undiminished in size and shall provide an open area of not less than 12.5 square inches (8065 mm2). Also, the 4" round ductwork in the walls cannot be deformed, it must retain its round profile.

• Each vertical riser must be provided with the means for a cleanout. What does this mean? This translates to having an accessible opening to remove the lint accumulation that settles in the lowest point of a vertical duct run. Professional engineers are in full support of the well-designed Dryerbox as it meets the requirements as a cleanout opening. The Dryerbox transitions the dryer’s flexible connection to the dryer’s exhaust duct through the wall. Learn more about Dryerbox here.

• View the Building Code Documents:2021 IMC - International Mechanical Code (section 504) and the 2021 IRC - International Residential Code (section 1501).

• View the "Dryer Venting Guidelines" here.

• Download/print the "Sealed Engineers Letter" regarding the cleanout issue.

It's important to adhere to the code for dryer exhaust venting. Taking shortcuts could pose a fire hazard and possibly void the manufacturer’s warranty on the dryer.

Back to All Articles