How Big Should a Stone Hearth Be for a Wood Burning Insert?

Answer

Installing a stone hearth underneath a wood-burning insert in your fireplace may help you turn your house into a cosy and welcoming space that serves as the home’s focal point. The brick or concrete pad that your insert rests on is referred to as the hearth. Additionally, the hearth refers to the extension or visible area that spreads forth into the room. The fireplace hearth size requirements determine the minimum measurements that must be met in order to help protect the wood framing and subfloors of your home from the extreme heat that can be produced by the insert. These requirements are the same regardless of the type of stone that your hearth is made of.

Tip

At the very least, the hearth extension need to protrude sixteen inches into the room.

Interior Hearth Dimensions

According to This Old House, the construction of the hearth of your fireplace starts on the inner of the firebox. It is possible for it to be formed of concrete, brick, or masonry, and the size of it is determined by the size of the firebox as a whole. If you are building a new firebox and hearth solely for the purpose of accommodating a new wood-burning insert, the size of the hearth will be determined by the size of the insert; the interior depth and width of the hearth will match the depth and width of the wood-burning insert. If you are building a new firebox and hearth solely for the purpose of accommodating an existing wood-burning insert, the size of the hearth will be determined by the size of the firebox.

Hearth Extension Size

You should always plan to expand your hearth outward into the room, regardless of the size of the wood-burning insert or existing firebox you have in your fireplace. The area of the fireplace that is visible to the user and is generally covered with ornamental stone is referred to as the hearth extension. According to the International Residential Building Code (IRC), the extension of the hearth should extend a minimum of 16 inches into the room from the edge of the firebox, and a minimum of 8 inches should be maintained on each side of the opening of the firebox. This helps to protect your flooring from damage caused by heat.

To calculate the completed size of your hearth extension, measure from the framed firebox outward, and then take into consideration the breadth or size of the surround. For an effect that is aesthetically attractive, the hearth should have the same dimensions as the surround. Before designing the hearth, you should check with your municipality to see if there are any changes in the local construction regulations.

Thickness of the Hearth

Hearth pads made of concrete or brick absorb the majority of the heat that is produced by your insert. As a result, it is necessary for them to prevent heat damage to the subfloor and frame that lies underneath them. A minimum of four inches is required for the completed height or thickness of the hearth that sits underneath the wood-burning insert. The extension of the hearth, on the other hand, ought to have a thickness of no more than two inches at the very least. This might include any stone that you want to lay underneath the insert or on top of the hearth expansion.

The thickness of the majority of stone tiles ranges from around 3/8 to 1/2 inch; take these measures into consideration and add the required thickness of backerboard to the concrete or masonry to reach the suitable finishing height.

Exceptions to the Hearth Rules

Both wood-burning inserts and firebox apertures are available in a dizzying array of dimensions and configurations. According to national building codes, the size of your hearth extension needs to increase to a minimum of 20 inches from the front of the firebox and 12 inches out to each side past the firebox opening if you plan on installing an insert that is a minimum of 6 feet square in size. This is the case if you plan on installing an insert that is smaller than 6 feet square in size.

You can reduce the thickness of your hearth extension to 3/8 inches if it is going to be raised up from the hearth to a minimum of 8 inches above it. This is the typical thickness of the stone that can be installed on it. If your firebox is going to be raised up from the hearth to a minimum of 8 inches above it. In addition, local building regulations could be different from these measures; before commencing construction, you should always check with the local municipality.