#Installing lath and plaster walls crack
#Installing lath and plaster walls windows

One-coat patching is not generally recommended by plasterers because it tends to produce concave surfaces that show up when the work is painted. When the base coat has set but not dried, more plaster is applied to create a smooth, level surface.

#Installing lath and plaster walls crack

If a crack seems to be expanding, a structural engineer should be consulted.įor small holes (less than 4 inches in diameter) that involve loss of the brown and finish coats, the repair is made in two applications.įirst, a layer of base coat plaster is troweled in place and scraped back below the level of the existing plaster. The crack is patched with an appropriate plaster in three layers (i.e., base coats and finish coat). The metal lath usually prevents further cracking. The debris is cleaned out, and metal lath applied to the cleared area, leaving the existing wood lath in place. Then, the plaster on each side of the crack should be removed to a width of about 6 inches down to the lath. When cracks are larger and due to structural movement, repairs need to be made to the structural system before repairing the plaster. The area is cleaned off with a damp sponge, then dried to remove any leftover plaster residue or dust. A third coat is applied to even out the surface, followed by light sanding. In this instance, a fiberglass mesh tape is pressed into the patching material.Īfter the first application of a quick setting joint compound dries, a second coat is used to cover the tape, feathering it at the edges. For more persistent cracks, it may be necessary to bridge the crack with tape. First the crack is widened slightly with a sharp, pointed tool such as a crack widener or a triangular can opener. For cracks that reopen with seasonal humidity change, a slightly different method is used. They may be filled easily with a patching material. Hairline cracks in wall and ceiling plaster are not a serious cause for concern as long as the underlying plaster is in good condition. Metal screeds are used to separate different types of plaster finishes or to separate lime and cement plasters. They are used to plumb and straighten uneven walls and level ceilings. Screeds are strips of plaster run vertically or horizontally on walls or ceilings. This calcium hydroxide reacts with carbon dioxide in the air to recreate the original calcium carbonate. After water has been added, it becomes calcium hydroxide. Found in limestone formations or shell mounds, naturally occurring lime is calcium carbonate. Gypsum is also the ingredient in moulding plaster, a finer plaster used to create decorative moldings in ornamental plaster work. For finish coats, gauging plaster was added to lime putty it causes the lime to harden. While gypsum was used in base-coat plaster from the 1890s on, it has always been used in finish coat and decorative plaster. When mixed with water, it becomes calcium sulfate again. When calcined (or heated), one-and-a-half water molecules are driven off, leaving a hemi-hydrate of calcium sulfate. Once mined from large gypsum quarries near Paris (thus the name plaster of Paris), gypsum in its natural form is calcium sulfate. Some time in the early 19th century, a transition occurred, and plasterers applied their wall finish before woodwork was installed. On early buildings, the woodwork was installed and primed before plastering began. Early plaster work, however, did not use grounds. These grounds help keep the plaster the same thickness and provide a stopping edge for the plaster.

#Installing lath and plaster walls windows

Plasterers use metal or wood strips around the edges of doors and windows and at the bottom of walls. Wire mesh used on inside corners of adjoining walls and ceilings. Installing the corner bead plumb is important.Ĭornerite. Installing the corner bread plumb is important. Wire mesh with a rigid metal spline used on outside corners. Like a wood ground, they indicate the proper thickness for the plaster.Ĭorner Bead. In the 19th century, metal casing beads were sometimes used around fireplace projections, and door and window openings. Fine sand can be added for a sanded finish coat.Ĭasing Bead. Pure lime, mixed with about 35 percent gauging plaster to help it harden, is used for the very thin surface finish of the plaster wall. With gypsum board lath (rock lath, plasterboard), it is the only base coat needed.įinish coat. The brown coat is the second application of wet, base-coat plaster with wood lath or metal systems. The wet plaster is “scratched” with a scarifier or comb to provide a rough surface so the next layer of base coat will stick to it.īrown coat. The first base coat put on wood or metal lath.