Final answer:
For a fireplace opening of 6 sq. ft. or more, the hearth should extend at least 15 diameters deep in front, and 8 diameters side-to-side to either side, adhering to newer recommendations for safety and efficiency.
Step-by-step explanation:
If the fireplace opening is 6 sq. ft. or more, the hearth should extend at least 15 diameters deep in front of the opening and at least 8 diameters side-to-side to either side.
This is based on newer recommendations that adjust the older "rule of thumb" to provide better safety and efficiency, particularly when using a wood stove or other efficient device. The increased depth and width of the hearth ensure that any sparks or embers that escape from the fireplace are less likely to reach combustible floor materials, reducing the risk of fire.
According to newer research, the hearth should extend up to 8 times the diameter of the fireplace opening side-to-side and up to 15 times the diameter deep. For example, if the fireplace opening is 2 feet in diameter, the hearth should extend up to 16 feet side-to-side and up to 30 feet deep.