In the Eastern States it is customary to fur around all chimneys with 2 X3-inch or zx4-inch studding, usually set flatways (except in outside walls), as shown in Fig. 186. The object of this is to form a nailing for the base, chair rail or picture moulding, and also to prevent the cracks that are almost sure to occur where a wooden wall joins a brick one. The studding should be kept at least 1 inch from the brickwork, and should be set plumb, bridged at least once, and the angles made square. If the chimney comes in a brick wall it is also usually furred around in the same way.
Fig. 187 shows the way in which a chimney which it is desired to have project on the outside of a frame wall should be built; a 4-inch lug being carried up on each side of the chimney, as at L, and the boarding and wall covering extending over it. While this construction can easily be made tight, it weakens the wall very much by cutting the girts and Plate, and should only be used with caution and not near an angle of the building.
When there is a fireplace the furring is set so as to form a breast wide enough to receive the mantel and an opening is left large enough to receive the facing around the fireplace opening, the facing being usually set flush with the plaster (see Fig. 169a, Part I.). Where there is a thimble for a stove pipe, a square opening should be framed in the studding opposite the opening, and at least 10 inches larger than the diameter of the pipe. The thimble is generally set so as to project \ inch from the brickwork, and the back of the recess is plastered directly on the chimney, while the sides are cased with wood, as shown in Fig. 188. This recess has a bad appearance, and a better way to do is to cover it with expanded or sheet metal lath, with a round hole for the thimble to pass through. A thimble 8 inches long can then be used and the breast plastered without a recess. The sides of the studding back of the plastering should also be covered with tin, so that there will be no danger from fire.
In some of the Western States furring around the chimneys is almost invariably omitted, and the author, after several years' experience with both methods, is of the opinion that, except against outside frame walls, it is better to use fire clay flue lining and then plaster directly on the brickwork. Where the chimney is furred it is difficult to completely stop the space at the floor levels, and if fire does occur it has a chance to make considerable headway before discovery. With flue lining, and the outside of the chimney plastered to the floor, there is no objection to nailing the base or other mouldings to the chimney, so that the only objection to this method is in the probability of cracks occurring in the angle with the woodwork. By building the chimney as shown in Fig. 189, and covering the flush side with metal lath, lapped on to the studding, there will not be much likelihood of cracks.
If the chimney is to be wainscoted the wainscoting must be kept outside of the plaster. Where the chimneys are plastered the breasts for fireplaces must be carried up in brick, but in many localities this is fully as cheap as furring and lathing, and certainly more fireproof.
When rooms are to be finished in the attic the studding at the sides and the collar or ceiling beams (see Fig. 79) are usually specified under the head of furring, and, unless they are required to support the roof, are put up after the roof is completed.