Older homes usually have plaster ceilings, which are durable and have soundproofing qualities. However, the plaster material has a tendency to crack with stress. The best way to cover the cracks in your plaster ceilings depends on the extent of the damage and the cause of the cracks. Smaller cracks require little time or effort to repair, while larger cracks can indicate a structural problem that may be difficult and expensive to correct.
If your plaster ceilings are mostly in good condition with a few hairline cracks, then you can easily fix them. These cracks probably appear only because of wear and tear or normal house settling over the years. The simplest way to cover such cracks is to simply fill them with a patching material such as drywall joint compound, flexible latex caulk or a special plaster patching compound.
Some cracks in plaster ceilings come back every few months or every year after you fix them. Plaster in older homes is applied to a wood lath system within the walls. When the humidity changes, the wood can swell or shrink and cause the plaster to crack. To fix these cracks, you have to first widen them with a tool such as a crack widener or a handheld rotary tool with a cutting wheel. Place mesh tape over the cracks and cover them with joint compound or plaster patching compound.
For cracks that come back again and again, you need something to hold the patching material and plaster together. If the cracks have caused one or both sides of the crack to lift, screw them back to the lath using drywall screws. Sometimes, washers and screws are used together to help distribute the pressure, preventing more cracks once the screws are tightened. Spread joint compound or plaster patching compound along both sides of the crack and cover it with a length of drywall tape. Drag the edge of a drywall knife over the tape to remove the excess compound. Apply a second coat of patching material to cover the tape, let it dry and sand the edges to smooth the border where it meets the plaster. Reapply the patching material and sand the area again if necessary.
If the cracks appear because your house structure is moving, you have to first fix the structural problem before moving on to the plaster. If the crack expands, you may have to hire a structural engineer to perform the repairs. After these repairs, remove the plaster to 6 inches away from the crack on both sides using a drywall knife or a rotary tool. Place a metal lath in the hole, then fill it with a patching material.
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