Since the fireplace is probably the most important feature of your
cabin, don’t skimp on materials. Buy the best dome-type damper that you
can afford. Some fireplace “experts” will say this is nonsense, but
don’t let them fool you. The damper is to a fireplace what a mainspring
is to a watch.
The dome damper is set on top of the fire brick lining where the throat
enters the smoke chamber. The handle to control it may be set in the
front or side as you wish (make sure of this when you buy it) and may
project or be set in a recess in the masonry.
The throat, as can be seen in Fig. 6, is considerably narrower from
front to rear than the fire box—5½ inches is maximum—and should come as
near the front as possible. It should begin 6 to 8 inches above the top
of the fireplace opening, extend the entire width of the fire box and
slant downward toward the back. At the same time the back surface of the
fire box has been slanting forward until it reaches the same height at
the beginning of the throat. At this point construct the smoke shelf,
which is literally a shelf set back to the vertical line of your
masonry.
[Illustration: An arch like this helps prevent downdraft.]
DIRECTION OF PREVAILING WIND
CHIMNEY CAP
Proper construction of the smoke chamber is often the factor that
determines the success of your fireplace. The amount of taper may vary,
but it is a good general rule to slope the walls inward one foot for
every 18 inches of height. The smoke chamber walls must be as smooth as
possible, the best finish being about ½ inch of mortar—or a commercial
steel unit. This cuts down the amount of friction and makes it draw
better. After the smoke chamber walls are tapered up to the desired
dimensions, the flue is straight from here on up.