This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
Fourthly, as to the chimney-stack -
1. The best position for a chimney-stack is on the ridge of the roof, some distance from the gable end. The slope of the roof not far from the ridge is also good, but the apex of a gable and the eaves of a roof are both bad. I do not mean to say that chimneys in these two positions will assuredly be smoky chimneys, but certainly the probabilities are that they will not be satisfactory.
2. A chimney which is overtopped by a building, tree, or rock, in close proximity, is sure to smoke when the wind is blowing over the obstruction, unless an efficient wind-guard at the top of the flue is provided; and what will prove an efficient wind-guard for a particular flue, who can predicate?
3. The walls of chimney-stacks should not be too thin, as thin walls chill the flue and check the draught; this is especially the case with lofty stacks. Here again the flue-pipes will be of service, and the walls may with advantage be 9 inches thick instead of the usual 4½ inches. When the walls surrounding the flue are 9 inches thick, there is no difficulty in obtaining good bond, but when they are only 4½ inches thick, much neat cutting is required, as shown in Fig. 66, which gives two courses of a brick chimney-stack in the usual stretcher-bond. Frequently in stone chimney-stacks with brick flue-divisions, no attempt at bond is made, unless the stone is lined throughout with brick.
When ornamental brick stacks are desired, specially-moulded bricks must be obtained, carefully designed to give proper bond, as shown in figs. 67 and 68.
4. Short flues are somewhat apt to smoke, a fault often remedied by raising the chimney-stack, or fixing a tall-boy on the top of it. Bylaws frequently insist that every chimney-stack must be carried at least 3 feet above the highest point at which it leaves the roof. This is intended as a precaution against fire; it is useful also in increasing the draught of the chimney. In any case, however, the chimney should be carried higher than the ridge of the roof.
5. Each flue should be finished in such a way as to separate it from its neighbours, so that the smoke from one flue does not find its way down the next not in use. This may be done by means of the simple cone-terminal, or short chimney-pot, or by one of the countless host of cowls, pots, and wind-guards. Special contrivances of this sort must sometimes be used, but into a discussion respecting them I may not enter space is limited. The inquisitive reader, however, will find descriptions of thousands of them in the Patent Records, if nowhere else.
Fig. 66. - Two Courses of 4½ Inch Brick chimney stack in Stretcher. bond.
Fig. 67.-Ornamental Brick Chimney-stack.
The subject of fire-grates will be treated in the section on Warming, but a few words must be said here respecting them. There are three main varieties of grate, each requiring a somewhat different treatment of the fireplace; these are the dog-grate, the hob-grate, and the ordinary grate enclosed on three sides and open at the front "fire-basket", is a detached receptacle for fire, placed in a recess, from the top of which the smoke-flue ascends. The grate is usually of iron, with perhaps some portions of brass Of copper, and in the better kinds the back and sides are lined with fire-clay. The heat radiated by dog-grates is small in proportion to the amount of fuel consumed, and as they are also provocative of dust, and somewhat apt to smoke, they are not often used except in halls.
Fig. 68 - Ornamental Brick Chimney-stack, with detached Shaft for each Fla*.
The dog-grate, or (as it is sometimes termed)
The recess for the dog-grate is usually formed with glazed bricks, which are often of small size, measuring only 4 J inches by 2 inches, or 6 inches by 2 inches, on the face, and 3 inches on the bad. The bricks can be obtained of various colours, printed, modelled, or plain, and with square or bevelled edges. Some-times ordinary unglazed facing-bricks are preferred. Fig. 69 gives a plan and elevation of a dog-grate recess; the width and height of the recess may be varied according to taste or the size of the room; the depth is usually 18 inches. The sides of the recess may be square, as at a, or canted, as at B, the latter being the better form. The brickwork is generally enclosed with woodwork of ornamental design, but faience and marble mantels are sometimes used.
The hob-grate is closely akin to the dog-grate, and partakes of the family faults. The recess is formed with ordinary brickwork to the top of the hobs, and above with glazed bricks or tiles, or with cast-iron plates, more or less ornamental. The glazed ware has the more pleasing appearance. The breasts and arch may be of similar character to those for a dog-grate; the hob-grate, however, must be accurately fitted to the opening, or vice versa. Instead of brick jambs and arch, faience blocks may be used.
The name of the "ordinary" grate is legion - from the old-fashioned, cast-iron register-grate to the newest "slow-combustion" fire-receptacle constructed wholly of fire-clay. Ordinarily, a simple opening is formed in common brickwork, as shown in Fig. 70, the opening being spanned either by a stone lintel or by a brick arch. The latter is often supported on a 2½-inch by ⅜-inch wrought-iron bar split at the ends, and turned up and down into the brickwork of the jambs. Into the recess a fire-grate is set, with such brickwork as may be necessary; and the common brickwork around the grate is faced with tiles, or slate or marble mantels, in hundreds of different ways. The recess is usually 3 feet high and 3 feet wide for rooms of moderate size, while for smaller rooms it may be made as narrow as 1 foot 6 inches. In the illustration the brickwork at the back and sides of the chimney-breast is shown 9 inches thick, and that in front only 4½ inches, but in good work a thickness of 9 inches should he maintained throughout; this not only lessens the risk of fire, but gives a firmer base for the chimney-stack, and affords a better bond for the flue-divisions.