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Metal Lath

house, plastering, water, surface and plaster

METAL LATH The best lath for exterior plastering is probably the No. 19 Clinton wire cloth. The wire is sufficiently large to be durable, and the mesh sufficiently open to allow the mortar to press through and completely fill and close in over the back of the wire, thus protecting it from expos ure to the elements or damage from water and rust, even if the plaster surface should leak sufficiently to admit water behind this covering. Expanded metal is also used for this purpose, but it is not generally considered so good a material, from the fact that it is impossible to cover entirely and protect the back of this lath with plastering, and therefore there is no means of certainly protecting it from the possi bility of rusting.

Occasionally, on a small, low house of not over a story and a-half of wall height, the boarding may be omitted altogether. The metal lath is then placed directly upon the furred studs, and plastered both outside and in to insure its absolute protection from damage by water. How ever, the shrinking of the studs opens a small crevice along each side— which has already been mentioned as occurring in back plastering— and it is thus possible that water may enter from the back and do con siderable damage, even through the narrow space that this shrinkage provides. The omission of the outer boarding also somewhat injures the stiffness of the house, as a frame constructed in this way is not so well braced as when the boarding is applied. Neither are the dwellers in the house so completely protected from the exterior weather, as the second air-space obtained between the papering and the exterior plastering is lost. This extra air-space is of assistance in keeping the house more equably warm in winter and cool in summer.

In the use of metal lath, it is always to be remembered that the absolute essential is to protect the lath from the action of water and rust. This once done—in whatever fashion—a permanent and last ing plaster surface is ensured. Sometimes the metal lath is wired and fastened to perpendicular iron flutings of tee-irons or angles, held to the wood frame with staples or some similar fastening, allowing any possible movement of the frame to occur without affecting or straining the plaster surface, which is by this means disassociated from, while directly supported by, the house frame. Cracks around the windows and the angles of the buildings are thus prevented; but it is a more expensive form of construction, and is not now employed except in the larger and more expensive residences.

From the use of wire lath, there are occasionally obtained small surface cracks, especially if the lath joint happens to come at a place where some strain is afterward placed upon it, and particularly where it is weakened from the movement of adjacent portions of the build ing. For instance, if a perpendicular lath lap is made on the line of the edge of the window finish, a crack on the line of this joint is almost certain to appear in the plaster, extending both above and below the wood-surrounded opening. Care should be taken to cut the strips of lathing so that the joint will come at least nine or ten inches on either side of the edge of the window or door finish. All furrings should also be kept away and back from all angles, internal or external, upon the walls, so that a certain clinch may be effected by the plastering at these important points.