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October 12, 2008
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Wood Stoves
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MSU Extension
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What's in this article
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 Introduction
Wall Protection
Floor Protection
Stove Pipe
Additional Precautions
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 Return to the Knowledge Base
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The hazards of heating with a wood stove include
fires started by heat radiated or conducted by the stove,
stove pipe or chimney to walls, floors and other
combustible materials; fires started by sparks and
glowing coals falling out of front loading stoves when
opened, and fires started by flames leaking out of faulty
chimneys or burning or glowing material coming out of the
top of the chimney. A chimney flow reversal is also
possible, leading to either flames or smoke coming out of
the stove's air inlets.
Before installing, seek advice from your stove
dealer, your local building inspector or fire department.
And check with your insurance agent. The insurance
company may have its own specifications for installation
and, since you are changing the method of heating your
home, your agent must be notified in order to maintain
fire insurance coverage on your home.
The National fire Protection Association (NFPA) has
developed standards for clearances from walls and
ceilings that are the basis for many local building
codes. See Table 1.
 Table 1 - NFPA recommended minimum* clearances frp, combustable walls** and ceilings |
All combustible materials, woodwork,
unprotected walls, furniture, firewood, etc., should be no
closer than 36 inches to a wood stove. A stove pipe should
not be closer than 18 inches to an unprotected ceiling.
These distances are important because wood that is,
continually reheated will ignite at much lower
temperatures than fresh wood. A new wall will start to
burn at between 500 and 700 degrees F. If this wall is
continually heated over a period of time the wood will dry
and eventually may start to char because of radiant heat.
The ignition temperature can drop to 200 to 250 degrees F.
For this reason an improper wood stove installation
becomes a potential time bomb. Figure-1 shows proper
installation.
Wall Protection
A simple test will tell if you have enough clearance
to an unprotected wall. Place your hand on the closest
surface. If you can keep your hand there comfortably
while the stove is operating, the location passes the
test. If not, you need additional protection.
Spacing asbestos millboard or 28 gauge steel 1-inch
away from the wall allows you to reduce the distance a
stove can be placed from the wall. (See Figure 2) These
materials absorb heat radiated from the stove and the
spacing lets air circulate behind the panel and cool the
area between the wall and the panel. The spacers should be
made of non-combustible material. A 1- to 1 1/2-inch gap
between the panel and floor and at the top of the panel is
necessary to provide proper air flow. Asbestos millboard
is different from asbestos cement board or asbestos
 Figure 1 - Proper wood stove installation |
transite board. Cement board or transite boards are both
hard, slate-like panel materials designed as a name
barrier. They provide little in terms of heat resistance
and will conduct heat to any combustible surface to which
they are attached. Asbestos millboard is a soft,
lightweight panel product that can be easily cut with a
saw or utility knife.
WARNING: Inhaling asbestos fibers may be harmful. The
effect of long term exposure is not completely known.
However, you should wear a protective mask when cutting
asbestos products.
Since brick and stone are good conductors of heat,
they offer little protection if placed against a
combustible wall or have wood studs behind them. To be
effective, bricks must be placed out at least 1-inch from
the wall with air gaps at the top and bottom. You can
provide these air gaps by using half bricks on the top
and bottom row. Stoves can be placed as close as 12
inches from the brick facing if you provide an air space
behind the brick.
An inexpensive and temporary way to protect a wall if
you already have a stove installed closer than 36 inches
to an unprotected wall is to provide a baffle. This
baffle could be sheet metal, hardware cloth or cement
board hung on metal brackets approximately 4 inches
behind the stove.
 Figure 2 - By providing wall protection, you can place a wood stove closer to the wall. Leave at least a 1 inch gap between the protection material and the wall to provide ventilation. |
Floor Protection
All floors on which stoves are installed, except
concrete, must be protected from both heat of the fire
and hot coals falling out when fuel is added. Metal with
asbestos backing and asbestos millboard are non-
combustible materials used for floor protection.
Fireproof clay tile, slate, brick, colored pebbles
and marble chips can be used alone only if they are
mortared in place with no gaps. If they are not mortared
or have gaps, then metal or asbestos millboard must be
installed between them and a wood floor. A 2-inch layer
of ashes or sand or bricks laid in the bottom of the
stove helps to insulate the bottom of the stove and
protect the floor. In general, 18 inches is enough
clearance to protect the floor if it is covered by
non-flammable material, such as a sheet of 24 gauge metal
or brick or fireproof clay tile. If the stove legs are
from 6 to 18 inches long, 24 gauge sheet metal laid over a
1/4-inch sheet of asbestos millboard is needed. Legs of 6
inches or less require 2 to 4 inches of hollow masonry
laid to provide air circulation and covered by 24 gauge
sheet metal. If the stove has no legs, provide a sturdy
support to allow air circulation under the stove.
The floor protection should extend at least 12 inches
beyond the sides and rear of the stove, and at least 18
inches beyond the stove front, to protect against falling
embers and for loading wood or removing ashes.
Before installing heavy protection materials such as
brick, check the floor to make sure it can handle the
increased weight. You may want to reinforce the joists
under the floor. Consult a carpenter if necessary.
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