0 56m the hearth extension shall extend at least 16 inches 406mm in front of the facing material and at least 8 inches 203mm beyond each side of fireplace opening.
Tile in front of fireplace code.
For a fireplace with a larger opening of more than 6 square feet the icc requires a hearth that extends 20 inches or more in front and 12 inches or more along the sides.
This is illustrated in the diagram below courtesy of the fine folks at code check.
When the opening of the fireplace is at least 6 square feet the hearth extension needs to extend at least 20 from the front of the fireplace and 12 on the sides.
2114 3 masonry fireplaces where the fireplace opening is less than 6 sq ft.
Mantel corbels and brackets attached along the sides of the opening must have additional clearance if they project more than 1 1 2 inches out from the face of the fireplace.
2114 3 masonry built fireplaces 4114 3 10 all combustible mantels and similar trim shall be kept at least 6 inches from the fireplace opening.
National standard building code information.
The firebox is where the actual fire will be and it must be lined with the appropriate materials that will meet building codes.
In the absence of local codes we suggest your installation clearances meet or exceed the national standard building codes or the national fire code.
National standard building code.
The surround is the front facing portion of the fireplace.
The hearth design must be.