This form of lathing is made from strips of thin and tough sheet steel, which are cut at regular intervals and then "expanded" by being wrenched or pushed into open meshes, greater or less, as the cuts are made longer or shorter. This expanding also turns the metal on edge, making a flat and stiff sheet of lathing much larger than the original piece of metal. (Fig. 241.) Having a degree of stiffness, this lathing does not require stretching, and it is used extensively for wrapping steel beams or columns for fireproofing or finishing, for thin partitions, and for concrete floors.

Fig. 239. Door Finish in Thin Partition.

Fig. 239. Door Finish in Thin Partition.

Fig. 240. Wooden Furring in Thin Partition.

Fig. 240. Wooden Furring in Thin Partition.

An objection is sometimes made to wire or expanded metal laths, that they require an excessive amount of plaster for ordinary uses. This may be overcome, when feasible, by the use of the Bostwick sheet metal lath, shown in Fig. 242. This is made from sheet steel by punching out loops at regular intervals. In this, and many other forms of sheet metal lathing, the surface is corrugated, besides being punched, to give stiffness and to keep the lathing away from the surface to which it is applied. Sheet metal lathing is easily adapted to the forming of coves or round corners, but for fireproofing the open lathing, requiring a greater amount of plaster, with the metal more thoroughly imbedded, is to be preferred.