Basic Hearth Dimensions

• To keep fire, ashes and embers a safe distance from the floor in front of a fireplace that has an opening 6 square feet or smaller, the hearth should extend at least 16 inches in front of the fireplace opening. The hearth also needs to extend 8 inches to each side of the opening. The thickness of the hearth should be a minimum of 4 inches.
  
  

Larger Fireplace Recommendations

• Fireplaces with openings larger than 6 square feet demand larger hearths. The front of the hearth needs to extend to a minimum of 20 inches, and the side areas need to extend to 12 inches. The recommended thickness for larger fireplace hearths remains the same.
  
  

Material Suggestions

• Stone, brick, concrete, concrete blocks or other noncombustible materials are recommended for hearths. If the hearth is so heavy that it requires underlying supports, they too should be fireproof.