Some minimum clearances from the fireplace opening should be adhered to for a proper fireplace mantle height. This is necessary to protect combustible materials from the burning fire in the firebox. The mantle you choose is a reflection of your personal flair and style. The design can be traditional or modern. The mantle's height, and other dimensions, should be in proportion to the fireplace opening and the size of the room.
Building Codes and Fire Safety
Visit the local building department to get the building codes pertaining to mantel installations, including the proper height and other measurements for the combustible wood or fibreglass board that mantles are usually composed of. If you purchase a mantel kit, read the owner's manual for more information on proper clearance requirements.
The proper fireplace mantle height has to be measured in multiple ways when ordering or building the final product. There is the total height of the mantle, the height of the columns or legs and the height as it relates to the opening of the fireplace and combustible facing material. The total or overall height of a mantle can range from 54 to 64 inches tall. The height of the legs is the distance between the floor and top of the column where the mantle connects to the shelf.
The fireplace opening height is measured from the top of the opening to the floor of the fireplace or ash pit. Usually the height of the mantle should be at least 20 inches above the fireplace opening. However, always check with the building inspector for the rules in your area.
Whether you are buying a mantle kit or building your own, these dimensions must be taken into account. You can purchase mantle kits, which have standard heights. You usually will need to provide the dimensions for the fireplace opening. This is required so that the vendor can incorporate the clearance requirements into the mantel design.
Some other important dimensions to consider when installing a fireplace mantle are: the length and width of the shelf; height of the hearth (for raised hearths); height of the facing material, which may extend from the floor to the top of the frieze or facing; the total width of the facing material; and the width of the facing material on each side (along the legs).