Slightly undercut the edges of the existing plaster to create a solid bond with the new plaster. First, using an old chisel or putty knife, remove any loose or crumbling plaster in the area that is to be repaired. Here’s how to take the sag out of your plaster ceiling using these nifty little gadgets. The disc also has many smaller holes scattered throughout its body into which spackle or drywall joint compound attaches itself to conceal the repair. The disc has a countersunk hole in the center through which a drywall screw is inserted. Many years ago a caller to our nationally syndicated radio program made us aware of a little known plaster repair device called a “plaster washer,” – a round metal disc about the size of a quarter (actually about one inch in diameter), which is used to hold up a sagging ceiling. Such was the case in the holiday classic movie National Lampoons Christmas Vacation when a bumbling and unsuspecting Chevy Chase went crashing through the ceiling onto a bunk bed below. Often it is caused when someone missteps in the attic – setting foot on the lath rather than on ceiling joist. However, a sagging ceiling isn’t always caused by a broken key. This occurs when the key breaks and positive connection to the lath is lost. One of the most common problems with plaster is a sagging ceiling. Anyone with plaster can tell you how it cracks and just try hanging a picture in plaster – yikes! And a plaster finish is infinitely more difficult to patch than drywall. Like anything else, plaster has its drawbacks – price aside. Drywall is cheaper to produce and install. The obvious question is “why isn’t it used as it once was?” The answer is simple – money! Interior lath and plaster is expensive. It is strong, has a uniform finish and can last forever. Thus, the best laid plans of mice and men. Ample fastening prevents the lath from pulling away from the framing. The key prevents the installed plaster from pulling away from the lath. The excess plaster that dries behind and around the lath is referred to as the “key” – essentially locking the plaster to the lath. Portland cement plaster was painstakingly hand-troweled onto wood slats (lathing) nailed to the wall and ceiling framing. I use all-purpose, ready-mix joint compound for the succeeding coats, and I apply these exactly the same as if I were finishing drywall.Before the advent of prefabricated wallboard or “drywall” in the 1940s and ‘50s, plaster was the material of choice for interior walls and ceilings in American homes. Durabond is almost unsandable, though, so I make sure to wipe the edges and overlaps clean. The advantage of using Durabond (over a traditional plaster) is that it sets up as hard as plaster but dries quickly, so if I’m in a hurry I can apply a second coat the same day. After packing the joint with compound, I cover the seam with fiberglass mesh tape, and follow up with a second layer of compound. I use a setting-type joint compound like Durabond 90 to fill the gaps, mixing up only as much as I can apply in about an hour. When all of the washers have been fastened, I vacuum the crack to remove any debris, then lightly mist the surface with water to prevent the dry plaster and lath from drawing moisture out of the patching compound before it’s had time to cure. After wiping away the excess joint compound, the crack is covered with fiberglass mesh tape, which is soon covered with a second layer of compound.
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