What Kind of Wall Board Goes Behind a Wood Heater?

Wood Stove Basics

• Of all forms of heat, an open flame offers the least amount of control over its operation. Whereas furnaces and other types of heaters operate on the principle of a controlled burn and a gauged output of heat, a wood fire gives off heat proportionate to how fast and hot it's burning. While a smoldering fire radiates very little heat, roaring flames can produce temperatures from 400 to 900 degrees Fahrenheit in a very short time. Unprotected surfaces exposed to this type of radiant heat over a long period of time dry out quickly, sometimes with disastrous consequences. The absolute minimum safe clearance for a wood stove installed near unprotected walls is 3 feet from the back, sides and along the length of the stove pipe, which also gets extremely hot during burning.

Stove Board

• Stove shops and many hardware stores carry stove board, which is pre-cut sheet metal over a layer of fire-resistant mineral board. Many styles of board are available, ranging from lower-priced plain flat surfaces to textured or designs that resemble brick or stone. To meet safety codes, the stove board must be installed with 1-inch spacers. The space created by this installation allows air to circulate between the board and the combustible surface, greatly reducing the amount of heat the wall is exposed to. A wood heater can be safely installed 18 inches away from surfaces protected by stove board.

Sheet Metal

• Used as a wall protector behind or near a wood heater, sheet metal provides the same benefits as UL-listed stove board. The metal should range from 24- to 26-gauge, with the lower number indicating a thicker gauge. Like approved stove board, sheet metal used to reduce wood heater installation clearances must be mounted to the walls on 1-inch spacers to allow for air circulation. Unlike stove board, sheet metal can be cut to fit unconventional installation areas.

Considerations

• The only instance in which surfaces do not need to be protected is if the wood heater is installed on a hearth that is constructed entirely of brick or stone. including the back and side walls. If the wall behind or near the stove is framed with wood, it must be protected with sheet metal or stove board as the bricks may get hot enough to dry and heat the framing lumber to the point of combustion. Also, no protection is needed if the heater is installed inside an existing fireplace.