If You're Going to Live in the Country

by Thomas H. Ormsbee; Renee Richmond Huntley Ormsbee

Between the lintel of the fireplace and the point where the flue commences come the three structural features so stressed by Count Rumford. They are the throat, smoke shelf, and smoke chamber. As its name implies, the throat is the opening through which smoke, hot gases, and some flames pass on their way upward. Experts hold that its correct construction contributes more to the efficiency of a fireplace than any other feature, save proper flue design. The area of the throat opening should not be less than that of the flue and its length must be equal to the width of the fireplace. It should be located eight inches above the lintel. Under present practice, a cast-iron throat with a damper which can be opened and closed to regulate the up-chimney flow is standard. Also, when the fireplace is not in use, this damper can be closed and so prevent loss of other heat.

The smoke shelf comes immediately above the throat and is formed by recessing the brickwork of the back the full width of the chimney for at least four inches. With very large fireplaces, it may be as much as twelve inches. The object of this feature is to stop any accidental draft within the flue from going farther and blowing smoke out into the room. The area in between this and the flue itself is called the smoke chamber. Here the walls are drawn in with a gradual upward taper to the point where the flue lining begins. The chamber so formed can and does hold accumulated smoke temporarily when a gust of wind across the chimney top cuts off the draft for a moment.

In building chimneys, the old masons varied their structural ways and materials according to the part of the country in which they worked. New England workmen were partial to a central chimney, the core around which the house was built, and their usual material was stone. Occasionally brick was used but this material was more in favor with old houses of the middle states and the South. Here, instead of the central stack, a chimney was built in each of the two end walls. The climate was milder and the style of architecture, with central hall and stairway, made such practice desirable.

The mark of an old chimney is its massive construction. In those of the central type, it is not uncommon to find a foundation pier of ten by twelve feet in the cellar. This was laid dry and just below the level of the first floor, large transverse beams were put in place to support the hearthstones of the fireplaces above. Here dry work stopped and, from there to the chimney top, all stones were laid in a mortar made of lime and sand. At a point above the smoke chambers of the various fireplaces and the brick-oven flue (always a part of the kitchen fireplace) all came together in a common flue. Here the chimney gradually tapered to the top and was usually about three or four feet square where it came through the roof. Originally such chimneys were entirely of stone. Comparatively few are found in original condition today. Time and weather usually made repair or repointing of the portion above the roof line necessary and, in the course of it, brick was often used instead of stone.

By ample proportions the old masons achieved fire safety. This can now be accomplished with a distinct saving in space if one is building a new chimney. There are certain fundamental provisions as stated in the standard chimney ordinance cited above. These are tedious and complicated reading for the layman, but to architects, builders and masons, they simply mean standard workmanship and materials that have been used for years to insure correctly functioning chimneys. Possibly a brief resumé of these fundamentals is not out of place in order that the prospective country house owner may not demand the impossible in his schemes for convenient closets, cupboards, or even a stairway.

The chimney may be built of brick, stone, reinforced concrete, concrete blocks, or hollow tile of clay or concrete.

All chimneys should rest on an adequate foundation located below the frost line and both chimney and flues should adhere strictly to the perpendicular.

If an angle is necessary, it ought not to be greater than 45 degrees.

No offset should be over three-eighths of the total width of the chimney.

In laying brick or other material, care should be taken that all joints are tight and completely filled with mortar.