To secure a good draught the throat or lower opening of a fireplace flue should be small, so that no air may pass through it without first coming in contact with the fire and being thoroughly warmed. To accomplish this the back of the fireplace should be brought forward as shown in Fig. 169, and a heavy sheet iron damper should be arranged at A to slide back and forth and so regulate the draught as desired.
There are several forms of iron backs for fireplaces that are provided with sliding dampers for this purpose. The draught in a fireplace is also affected by the height of the fireplace opening above the grate, which should not exceed 24 inches, the usual height of the opening above the hearth being 29 or 30 inches. Where there are fireplaces the bottom of the "chimney is generally built hollow, so as to receive the ashes from the grates above, and flues should be provided, as shown in the illustrations, for the ashes to pass through. A cast iron ash door should be built in the bottom of the ash pit to permit of removing the ashes. The hearth is generally supported by a trimmer arch (as shown in the figure) springing from the chimney and resting against a header framed in the floor. The space above the arch is filled in with concrete and leveled off with cement to receive the tile.
The facing of a fireplace should project 4 inches beyond the rough breast, so as to bring the grate forward as far as possible, as the further the grate projects into the room the more heat it will give out.
Nogging is a term that is applied to brickwork filled in between the studding of wooden partitions. It is often employed in wooden partitions of dwellings and tenement houses to obstruct the passage of fire, sound and vermin. As no particular weight comes upon the brick, and they are not exposed to moisture, the cheapest kind of brick may be used for this purpose-
The brick should be laid in mortar, as in a 4-inch wall. If the partition is to be lathed with wooden laths it is necessary that the width of the bricks shall not be quite equal to that of the studding, to allow for a clinch to the plaster. When 3¾-inch studding is used it will be necessary either to clip the brick or lay them on edge.
When the studding of a partition rests on the cap of the partition below it is an excellent idea to fill in the space between the floor and the ceiling below with nogging to prevent the passage of fire and mice, and two courses of brick laid on horizontal bridging is also a good means of preventing fire or vermin ascending in a partition.
Soon after the walls are completed all pressed or face brick should be washed and scrubbed with muriatic acid and water, using either a scrubbing brush or corn broom. The scrubbing should be continued until all stains are removed. At the same time all open joints under window sills and the joints in the stone and terra cotta work should be pointed, so that when the cleaning down is completed the entire wall will be in perfect condition.