Wisconsin State Building Codes for Fireplaces

Masonry Fireplace Flue Regulations

• According to the Wisconsin Department of Commerce, flues that are round can take up 1/12 of the fireplace's opening but cannot be less than 75 inches. Flues that are rectangular or square can take up 1/10 of the fireplace's opening and also cannot be less than 75 inches. Flueliners must be installed and begin at the bottom of the fireplace and extend at least four inches above the cap of the chimney. Flueliners should be made of material that will not corrode, soften or crack under high temperatures. Firebrick can be used to supplement flueliners at the bottom of the fireplace.

Masonry Fireplace Chimney Regulations

• Chimneys must be at least three feet in height from the highest point in the chimney's intersection with the roof. Chimneys also must be at least two feet higher than other part of the house within 10 feet of the chimney. Chimney walls must be a least four inches in diameter. Chimneys cannot be made out of or rest upon wood.

Masonry Fireplace Hearth Extensions

• Each fireplace must possess a hearth made out of noncombustible material that is reinforced by at least four inches of concrete. The hearth size is determined by the square footage of the fireplace opening. If the fireplace opening is less than six square feet, the extension of the hearth must be eight inches to the side and 16 inches to the front. If the fireplace opening is greater than six square feet, the extension of the hearth must be 12 inches to the side and 20 inches to the front. There cannot be any wood built into the hearth.

Masonry Fireplace Cap, Damper and Hood Regulations

• Chimneys must possess pre-cast concrete chimney caps which should have a minimum thickness of two inches. Chimney caps should also slope away from the flue and have a one-inch overhang on all sides, allowing for drips.

  Fireplace dampers must be made of a sheet metal of at least No. 12 gauge. When open, the damper should be at least 90 percent of the flue area.

  Metal hoods must be constructed of a corrosion-resistant, smokeproof sheet metal of at least No. 19 gauge. The hood must slope at an angle of 45 degrees or less and must extend at least six inches from the edge of the firebox. Metal hoods must be kept at least 18 inches from the nearest combustible material in the home.

Factory-Built Fireplaces

• Factory-built fireplaces should possess a fire chamber, one or more chimney sections and a roof, all of which must be tested by a nationally recognized laboratory. When assembling a factory-built fireplace, all manufacturer regulations and instructions must be met and followed, including regulations for the hearth extension. A factory-built fireplace must be installed away from all combustible materials in the home.