Making a Fireplace Part 1

Making a Fireplace.

by Henry H. Saylor.

INTRODUCTION

In a book of this kind there is no particular need for dwelling at length on the desirability of having a fireplace. That will be taken for granted. It is enough to say that in these days a home can scarcely be considered worthy of the name if it does not contain at least one hearth. There is some inexplicable quality in a wood fire that exerts almost a hypnotic influence upon those who eagerly gather about it. The smoldering glow of the logs induces a calm and introspective mood that banishes all the trivialities and distractions of the day's work and gives one an opportunity to replenish his store of energy for the coming day.

The open fire, unlike most of the comforts that we demand in a modern home, has been a.s.sociated with the race as far back almost as the home itself. At first, of course, it was as a necessity and the development from that to a luxury has been an exceedingly slow one extending over the years down to the present time.

There are two forms of the open fire-a possible third one, the gas log, being a subject on which the less said the better. We have, therefore, a choice between the open fireplace designed for wood and the basket grate in which to burn coal, preferably cannel coal. This latter fuel is not nearly so well known in this country as in England where the scarcity of wood necessarily makes coal the more commonly used fuel. With our own abundance of wood, however, there will perhaps be little hesitancy in choosing the open fireplace rather than the basket grate for coal, although in certain cases, for example an apartment where the flue has been built too small, or in a house where an available chimney offers only a small flue area for fireplace use, the basket grate will prove a welcome solution of the problem. Of course there is no excuse whatever for building a modern home with a chimney too small for the sort of fireplace you want, but where the chimney has already been built without this provision it may possibly be found that a small terra cotta flue lining may be inserted in the larger flue without seriously damaging the latter's power of draft. In that event the addition of a basket grate fireplace to an old house would be an interesting possibility.

However fully we may appreciate the desirability of some sort of fireplace, there seems to be a rather widespread impression that the attainment is largely a matter of chance. Too many home-builders have instructed their architects to provide a fireplace or two in the fond hope that the matter was then practically closed-a mere matter of time until they might be sitting before the fire's cheerful glow. Too frequently the result has been a disappointment when the first few trials introduced into the room more smoke than heat or cheer. The reason for this is that there is a scientific basis for fireplace building which is frequently ignored absolutely by an over-confident and stupid mason. Where the work of building the home has been entrusted to an architect's hands the latter usually appreciates the fact that the building of the fireplaces is liable more than any other part of the house to be taken into the mason's own hands with, if he is not watched, disastrous results. Undoubtedly every mason would resent most strongly any insinuation as to his lack of knowledge regarding fireplace construction. Each mason not only thinks that he knows how a fireplace should be built, but it is almost as general a rule that he feels that his particular method is the only correct one.

[Ill.u.s.tration: One of the best forms of the basket grate in bra.s.s. The splayed sides send out more heat]

[Ill.u.s.tration: A modern English fire corner. Facing and hearth have been worked out in a rather startling contrast of tiles]

In view of this it might be well for any man building his own home to give some attention to the matter of his fireplaces, to insist on knowing how they are designed and to follow their construction throughout so that there is no chance for a blunder; and this chance is not so slight as might be supposed. In a house in which the author had carefully shown every detail of construction in the drawings, it was found when the building was nearly completed that the cast-iron throat flues, which ordinarily prevent any possible mistake of construction on the mason's part, had been put in reversed and it was necessary to tear down the whole face of the chimney breast in each case to replace them properly.

The matter of construction is not at all a complicated affair, as the next chapter will aim to show.

CONSTRUCTION

The chief difficulty in attaining a successful fireplace design does not lie in securing an abundant draft. In fact it is an easy matter to make a fireplace draw if the flue is large enough and the opening from the fire chamber into the flue un.o.bstructed. There will never be any question of getting a roaring blaze the moment the fire is lighted.

This is, in a way, the type of fireplace that our Colonial ancestors built-great cavernous openings and generous flues, with the result that the more wood was piled upon the blaze the more they blistered their toes and at the same time chilled their backs. For it is evident that when we secure such a strong, un.o.bstructed current of hot air up the chimney, enough cool air to take its place must be drawn into the room through every opening and crevice. The result is a mighty draft that rushes past those unfortunate enough to be sitting about the fire and carries rapidly up the chimney almost all of the heat of combustion.

In the fireplace of our Colonial ancestors probably ninety per cent. of the heat was entirely lost, being carried up the chimney. However, cord wood was then to be had for the cutting.

We want a different sort of a fire in these days-one that will burn with a steady, constant blaze or glow, conserving most of its heat, which the back and sides of the fire chamber will reflect out into the room.

Such a fireplace will not necessarily be a large one. It is amusing to hear how universally the demand goes up for large fireplaces-"great big fellows that will burn full cord wood." It is hard to see just why this is. It may be based on the a.s.sumption that if a small fireplace is desirable a large one is more so. This is a fallacy that the architect and fireplace builder find it hard to dispel. There is no objection whatever to a large fireplace in a summer camp or informal shack of that sort. In fact a small one would in such a place be ridiculous, but when we come to our year-round living-room or dining-room or den, where the walls of the room are tight and the whole atmosphere quieter and more restrained, a large fireplace would be distinctly a disturbing element.

Such a room as this, unless very poorly built, would not permit the in-take of sufficient air for the draft of a big fireplace, whereas in our slab cabin or log bungalow the conditions are quite different.

[Ill.u.s.tration: A section through the fireplace and chimney. The broad cross-hatching represents brickwork]

For the ordinary room, therefore, a fair average size for the fireplace opening is three feet in width by two and a half feet high, with a depth half the width. From such a fireplace it is possible to get a maximum of heat with a minimum of draft.

There are two vital principles that should be observed in the design of any fireplace. One of these is the relation between the size of the opening into the room and the size of the flue itself. A cross-section of the flue-which incidentally should be kept the same throughout its extent-should be one-tenth of the area of the opening into the room.

The second vital consideration is the introduction of what are known as a "smoke shelf" and a "smoke chamber." The reason for constructing a fireplace with these two features will appear more readily by reference to the diagram. This is drawn to show that when a fire is kindled on the hearth the warm air current, which is generated immediately, begins to rise through the throat (the opening between the fire chamber and the smoke chamber) and at once induces a down-draft of cold air. If the back of the fireplace were on the same continuous plane with the rear side of the chimney flue, this downward current of cold air would strike directly upon the fire itself and force smoke out into the room. The smoke shelf is built just where it will prevent this action. The sectional diagram does not perhaps make quite clear the shape of this smoke chamber, but the accompanying perspective outline sketch will indicate the fact that the throat and the smoke chamber at the bottom must extend across the full width of the fire chamber. This width in the smoke chamber immediately diminishes in rising until it joins the flue at the flue's own area.

The sectional diagram indicates a cast-iron damper built in the throat.

This is not necessary, for it contributes nothing to the efficiency of the fire itself. Its one great advantage is that by furnishing the mason with an unalterable form, it forces him to build the throat properly rather than in one of the wrong ways that his own judgment might dictate. Such a cast-iron damper also forms a support for the flat arch of brick over the opening if bricks are used. If the damper is not built in, it is necessary to use an iron supporting bar to carry this flat arch. Then too, in case the damper is not used, there is lost the advantage of being able quite readily to close the throat entirely, which is highly desirable in the summertime and frequently in the winter when the fireplace is acting too strenuously as a ventilator. If the cast-iron throat is not used, therefore, it will be well to lay an iron plate on the smoke shelf in such a way that it could be drawn forward across the opening to close it.

[Ill.u.s.tration: Perspective view of the fireplace, showing the shape of the various parts as built without a cast-iron throat damper]

There are other types of dampers, most of them patented and all of them aiming to provide an adjustable opening in the throat in some way. One or two of these have a k.n.o.b or handle projecting through the brickwork of the arch, permitting the convenient adjustment of the damper from outside. As a general principle, however, it is well to choose the simplest possible device that will secure the desired result.

The terra cotta flue lining which is shown in the sectional diagram is not absolutely necessary, of course, as it is a rather modern introduction and unnumbered fireplaces have served their purpose without it. There is no question, however, regarding its worth, for it provides a flue with smooth, regular sides that will not clog nearly so readily as an ordinary brick flue. Besides that, it has the advantage of permitting a thinner wall for the chimney. It is dangerous to build a chimney with a single four-inch thickness of brick between the flue and whatever may adjoin the chimney. Of course no wood should be allowed to come within an inch or two of the brickwork in any event, but with a single thickness of brick, unlined, there is always the danger that the mortar will crumble from a joint and leave an opening through which it would be an easy matter for sparks or flame to do considerable damage.

The introduction of a flue lining, however, into the chimney built in this way makes it entirely safe, provided the joints between sections of flue lining are carefully filled and made smooth with cement mortar.

The sectional diagram, it will be noticed, indicates a difference between the main back wall of the chimney, eight inches thick, and the brickwork laid inside the fire chamber to form the hearth and the back.

The reason for this separation is that the rough brickwork of the chimney is always laid first as simply as possible, leaving the fire chamber with its sloping back and sides and the hearth to be filled in later with a better grade of brick or perhaps another kind. Frequently, also, tile will be combined with the brick finish as a hearth or facing.

[Ill.u.s.tration: A cross-section showing the construction of a large stone fireplace with slightly arched opening]

A support for the hearth is usually obtained as indicated-by bringing what is called a "row-lock" or "trimmer" arch between the foundation masonry of the chimney and a pair of floor joists set out at the proper distance, depending upon the desired width of the hearth. While this is the customary method, occasionally a support is secured in some other way, such as corbeling out from the masonry foundation, or by extending two short projections of this masonry from the bottom up at either end of the hearth and throwing an arch across between these. Upon a bed of cement the hearth bricks themselves are laid, usually flush with the floor, although occasionally enough higher to permit a beveled molding strip to cover the joint between brick and floor more closely. In some cases the hearth itself is raised the full thickness of a brick above the floor, as in one of the photographic ill.u.s.trations shown.

The width of the hearth is ordinarily made about sixteen or eighteen inches beyond the face of the opening with the average size fireplace, twenty inches or even more with larger ones. This width should be increased, of course, if the opening is made considerably larger. The question of materials for the hearth and facing will be discussed in the next chapter.

The chimney itself should extend at least a foot or two above any nearby roof ridge and it should work without any cowl, whirligig or other device of that type on the top. There is no great objection to having the opening a horizontal one at the top of the chimney, although in that case if the flue is nearly straight throughout its course, some rain will find its way down to the hearth in a hard storm. In most cases there is enough bend in the flue to prevent this, and if not it may be avoided by covering the top of the chimney with a stone and having the openings vertical ones on all four sides just under this.

All of the brickwork throughout chimney and fireplace should be laid in first-cla.s.s cement mortar which consists of one part Portland cement to three parts clean, sharp sand. Although lime mortar was used in all brickwork up to recent years, it is not durable, particularly in the vicinity of heat.

MISCELLANEOUS ODD FORMS

There are many unusual forms of fireplace with which we are not particularly concerned. For example, one sees occasionally an opening shaped like an inverted heart or like an ace of spades. It is possible to make a fireplace of this kind work satisfactorily, but it is by no means certain that this result can be accomplished at the first trial nor that the fire will continue to work properly under all conditions.

It is safer always to adhere to the established type of rectangular opening, or to depart from this only to the extent of having the top an arch of large radius. Whenever the top is permitted to vary more than a slight extent from the horizontal there is the danger of having the smoke escape into the room at the top.

[Ill.u.s.tration: The inglenook seldom fails as a dispenser of home cheer. Frequently the seats are placed too close to the fire]

There is one other type that deserves special mention and that is the double fireplace, where two openings in adjacent rooms are served by a single flue between them. The only way in which this affects the two vital principles mentioned above is that the cross-section area of the flue should be one-tenth of the combined areas of the openings. The throat will in this case be in the middle of the chimney with the smoke shelf on either side of it. It is essential in a fireplace of this kind that there be no disturbing draft tending to pa.s.s through the opening from one room to the other.

Still another type which is even more rarely seen is the open fire in the middle of a room, such as may be desired occasionally in the lounging room of a large club. Such an apparent anomaly could be secured by suspending a metal flue and hood from the roof, so that the lower edge of the truncated pyramidal form at the bottom would form the upper side of the fireplace "opening" at a convenient height above the hearth of brick, stone, tile or concrete. It is conceivable that an effective and thoroughly practical fireplace could be thus devised, having the flue and hood of wrought iron or copper, suspended and steadied by chains or bars from the ceiling and surrounding walls. In such a form the same principle of a fixed ratio between opening (here the entire perimeter of the hood multiplied by the distance above the hearth) and cross-section of flue would have to be observed, and here also it would be well to provide as fully as possible against the presence of disturbing drafts.

FACINGS AND MANTELS

There is not a particularly wide choice of materials available for the finish of the hearth and fireplace. Stone, brick, cement and tile exhaust the possibilities, although with combinations of these we have all the variety that we could wish.

Stone is suitable only in certain environments-the informal shack or log cabin chiefly, though of course it is impossible to make any hard and fast rule in the matter.

Brick is almost never out of place. Perhaps it is the a.s.sociation with the fireplaces that have been built by our fathers and grandfathers, or perhaps it is the inherent worth and fitness of the material itself that puts it forward as a first choice. Undoubtedly the practical consideration that it is easier and more economical to build has something to do with the matter.

Concrete is a newcomer in the field of fireplace facing and as yet it cannot be said to have shown any particular reason why it should displace the other materials. With the ordinary heat developed in an open fire of wood there is no likelihood of cracking the concrete facing if the material has been properly mixed and applied, although there seems to be a vague impression that this might be a real danger. The color of concrete gives it no particular recommendation, for it is one that remains unchanged by fire, though not unstained by smoke. Brick, on the other hand, and tile, have the very closest possible a.s.sociation with fire in the making, which gives them a peculiar fitness for this purpose.