Sunset's Cabin Plan Book

by Unknown

BUILDING THE CABIN FIREPLACE

If the chapters in this book were arranged in the order of their importance from the standpoint of cabin features, this one, dealing with fireplaces and chimneys, would probably come first. No matter what other ideas you may have about a vacation cabin you will undoubtedly insist on a fireplace as a dominant feature. To most people a cabin without one just isn’t a cabin at all.

When it comes to building it you can have the work done a lot easier than you can do it yourself. On the other hand, you’ll probably do a lot of arguing with the mason because, strange as it seems, there appear to be comparatively few masons who can build a fireplace and a chimney that will work to perfection. The instructions here have been collected from people who do know how, and if you follow them, you should have a successful fireplace.

In the preceding chapter you have read about the fireplace foundation. By the time the rest of the house is pretty well along this should be in good condition for the next step.

A fireplace consists of four essential parts: the fire box itself, the throat, the smoke chamber, and the flue. The shape and relationship of these are very important. One simple relation to remember is that the area of the fireplace opening should not be more than 10 times the area of the flue. Some people say 12 times, but 10 is a better average.

Fig. 6. Construction of fireplace.

THROAT OPENING FULL WIDTH OF FIREPLACE CHIMNEY FLUE FLUE LINING SMOKE CHAMBER SMOKE SHELF DAMPER THROAT 8″ FIREPLACE

The over-all dimensions of the fireplace, including mantel, are matters of proportion and taste, governed by the size and shape of the room. In almost every case the width of the opening should exceed the height. The top of the opening should be at least 30 inches from the floor but not much more than 40 inches unless it is at least six feet wide—and not many cabins can stand a fireplace as big as that. For a six-foot opening plan for a depth of about 24 inches. No fireplace should have a depth of less than 18 inches. Remember, however, that the deeper your fire box the less efficient it will be for heating purposes. The hearth should extend at least a foot on either side of the opening and have a minimum depth of 20 inches.

You may have the opening flush with the hearth, or, as some builders prefer, lay a course of stone several inches high across the lower edge and curve the bottom of the fire chamber up to it. Or you may elevate the entire bottom of the fireplace. It is smart to plan the hearth flush with the floor so that trash may be swept into the fireplace without using a dustpan.

Rough native stone, of course, is the most interesting material for a cabin fireplace and chimney. Brick seems too refined for the woods. If you want the finished job to look as massive in appearance as possible, don’t use stones that are too small.

The walls of a stone fireplace and chimney should be at least one foot thick. But as a concession to safety, the entire fire box—back, sides and floor—should be lined with good quality firebrick. The space between the stone shell and firebrick lining is filled with concrete. Since the back and sides of the interior must reflect the heat into the room, the back must be slanted forward as it rises, running up straight about one-third of the height of the opening from the hearth floor and then slanting toward the front at an angle of from 23 to 30 degrees. The sides should slope inward, as they approach the back at, roughly, an angle of 60 degrees.

Regardless of whether the top of the fireplace opening is flat or arched, you will need a strong support at this point. The best is an iron bar about one-half inch thick and two inches wide. Extend it across the width of the opening and set it firmly in the stonework at each side. Any blacksmith can make this bar for you, and the curve he puts in it will determine the arch of the opening. A “T” bar, set with the tail of the “T” upward, is even better, since it is stronger and requires less iron.

Behind the bar build a wooden form extending back several inches and sloped slightly upward. Then lay a course of stone on top of the iron and fill in between the stone and the form with a rich mixture of concrete reinforced with iron rods. This concrete should rise at such an angle as to come flush with the edge of the damper. The reinforcing rods should extend the full width of the arch and tie into the stone at the sides.