That layer is placed against the wall studs or in a masonry building against the masonry wall. Above the product includes an insulating layer of up to 1/2" of wood or paper fiber insulating board on its innermost layer. Never apply lime mortar, portland cement, any other kind of binding agent to gypsum lath.Īlso, perforated board lath should not be used on ceilings where it is supported only at edges, because the perforations weaken the lath.īut this is not the only type of plaster lath board or gypsum lath board found in homes. Watch out: only gypsum mortar can be applied over gypsum lath. Here is another example of perforated gypsum board plaster lath or rock lath, taken from a 1945 Greenville South Carolina home, courtesy of reader Our photo (above) shows mortar passing through the holes in perforated board lath. to provide mechanical keys, improving adhesion and fire rating of the surface. Gypsum Board Lath is provided in a variety of sizes, thicknesses, and types, most commonly 3/8" x 16" x 48" in dimension, solid or perforated with 3/4" diameter round holes punched 4" o.c. Board lath requires the least amount of mortar to cover the surface.Board lath is insulating, strengthens the framework of the structure, and the gypsum board is fire resistant.Board lath is rigid, strong, stable, and reduces the possibility of dirt filtering through the mortar to stain the surface.VanDenBranden/Hartsell explain the popularity of board lath as a plaster base : Hartsell, and in US Gypsum's Gypsum Construction Handbook as well as other publications. Kal-Kore plaster base is sold in 4' and 8' widths and in 8' to 16' lengths - considerably larger than the older plaster-board lath systems shown above and just below where we describe regular rectangular bulges in plaster ceilings and walls.īoard lath and how it is applied are described in Plastering Skills, F. Kal-Kore plaster base panels are designed as a base for veneer plaster, but these can also be used as basecoat plasters for Gypsolite, Two-Way Hardwall (National Gypsum products) or other conventional plasters. Here is another photograph of a PLASTER WALL TEST CUT that shows a closeup of the layers of plaster board and top coats that make up the wall surface in a 1930's-built home whose plaster-board lath included wood fiber reinforcing materials.Ĭontemporary gypsum lath products include GoldBond® brand gypsum board products including Kal-Kore brand plaster base panels sold by National Gypsum Corporation. Our wall cross section cutaway photograph of gypsum board lath installed on a New York home (photo at left) shows how these walls are constructed, and you can see quite clearly the top coats of plaster that were applied over the gypsum board itself. "Ears" of oozing plaster pushed through the round holes helped hold the plaster top coat in place A top coat of plaster was applied to the plaster board. Plasterboard with round holes punched at regular intervals substituted for the plaster scratch coat, nailed to wall studs, eliminating the wood lath requirement. Both perforated and solid gypsum board panels were sold for use as a base for finish wall and ceiling plaster. Our photo (above) shows perforated gypsum board panels that were used as plaster lath. Synonyms: Gypsum Board Lath Sheets Used for Plaster Walls & Ceilings = Rock Lath, Plaster Lath, Rock Lathe & Button Board Perforated Gypsum Board Lath Gypsum Board Lath Sheets Used for Plaster Walls & Ceilings = Rock Lath, Plaster Lath, or Rock Lathe We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. Here we will illustrate several types of gypsum board lath or "rock lath", including both perforated and solid gypsum board over which plaster was applied to form a finished wall or ceiling. Rock lath or button board was used as a base for wall and ceiling plaster systems as early as 1918. We have no relationship with advertisers, products, or services discussed at this website. InspectAPedia tolerates no conflicts of interest.
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