How to Repair Water Damaged Ceiling Plaster? When three-coat plaster is somewhat wet, the surface frequently shows various visual indicators. Ceilings and walls may develop a brown stain. The chemical reaction of the lime may cause the surface to bubble after a strong soaking. As the surface cures, it may harden and flake off the surrounding paint.
Water damage might be modest, affecting only the surface layer of the wall, or it can enter the entire three-coat structure, resulting in crumbling brown and scratch coats that fall off the lath. In some situations, the lath may be compromised as well, revealing decaying wood or corroded metal beneath the plaster layers.
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How to Repair Water Damaged Ceiling Plaster?
Wet plaster is best mended with setting-type joint cement, often known as mud. The ready-mixed compound is not hard enough and is susceptible to residual moisture in the wall material. This page describes how to repair water damage to the surface layers of plaster walls and ceilings. A video explaining how to repair water-damaged plaster may be seen here. If you have more significant plaster damage, such as wall material breaking off the lath, follow the steps in this link to fix it.
Step #1. Take out the damaged plaster
Before commencing repairs to water-damaged walls or ceilings, discover and stop the source of the leak, or you will be fixing the same damage again very soon. Also, let the plaster completely cure before attempting to begin repairs.
The first step in repairing something is to remove all of the damaged material. This includes any bubbling or peeling paint, cracking plaster coatings, or deteriorated lath. Remove flaking paint and bubbling plaster with a putty knife. To remove all of the soft, loose debris, use hard pressure with the blade.
Drill around the damaged area with the knife until you reach hard, undamaged plaster. Check to see if the paint coat directly surrounding the spot will simply peel off. Using a putty knife, remove any loose paint from the core of the damage.
Step #2. Seal Water Damage
Remove any loose particles from the surface with a stiff nylon brush and a shop vac. Before beginning, wash the surrounding surfaces with a sponge and pail of clean water to eliminate any remaining lime deposits and allow the wall to dry completely.
Coat the area with an oil-based or quick-dry primer-sealer after it has been cleaned and dried. Priming is required to prevent any leftover pollution from remaining on the surface and interfering with the bond with the patching material. It will also keep stains from leaking through the finished paint, which could cause the fresh paint layer to bubble.
To ensure that the primer is completely mixed, vigorously shake the can or stir it. Coat all impacted areas with the affected paint and overlap with the surrounding wall paint. Before applying any repair material, let the primer dry completely. Quick-dry primers dry in about an hour, however, oil paint might take up to 24 hours to completely dry.
Step #3. Fill in the Plaster Damage
Fill up the missing plaster and level the wall with numerous thin applications of joint compound to repair shallow surface damage. Apply a first coat with a modest amount of compound and a flexible joint knife. “Butter” the area with a 14-inch coat of mud, then go back over it to skim off the excess with parallel strokes from one side of the patch to the other.
Float the blade throughout the deeper damage to fill it in, and skim harder on the surrounding walls to leave a very thin coat there. To keep things level, don’t allow mud to accumulate higher over the repair area than it does on the surrounding surfaces. Also, avoid leaving thick mud all around the perimeter to avoid excessive sanding when you’re through.
If you need to repair a wide area, use a long, thin board, such as a piece of lattice moulding, to go over the entire area at once. To smooth out the high points in the overall repair, place the board on the surrounding area and drag it across the wet mud a few times. Ignore any ridges or irregularities in the mud surface. After it has dried, scrape off the excess mud before adding another coat.
Allow the joint compound to harden before using the joint knife to shave off any ridges or other roughness in the surface with an upward stroke. If necessary, use coarse to medium sandpaper to remove any remaining lumps, etc. It is not necessary to have a fully flat surface here; simply remove any high points. Brush away the dust and clean the surface with a clean, damp rag or sponge to remove the scraping and sanding dust before re-coating it with mud.
Step #4. Use More Joint Compound
Apply a second heavy application of mud to the surface, buttering it as before. Fill up the deepest sections of the damage first, then apply a light layer around the margins.
Skim off the excess mud immediately with parallel strokes, but this time in a perpendicular direction to the first coat. When you used horizontal strokes the first time, switch to vertical this time. Ignore any ridges left by the knife blade, but keep the mud as thin as appropriate on the surrounding wall surface to reduce sanding afterwards.
Scrape, sand, and wipe off the dust after the second coat has dried. Apply as many additional coats as necessary to cover all of the damaged plaster. Remember to avoid mud buildup on the surrounding surfaces and to switch direction with each new layer to maintain the repair level. Ready-mix joint compound can be used for the final coat of mud. This will make sanding a smooth finished surface easier.
Step #5. Sand and Apply Touch-Up Paint to Repair Water Damaged Ceiling Plaster
Allow the last coat of joint compound to cure and dry completely before sanding the whole patch with 120 sandpaper. Make sure to smooth the patch’s outer borders into the surrounding wall surface. Wipe away the sanding dust with a moist rag before priming the new repair and surrounding surfaces with the same primer-sealer that was previously used.
It is critical to use a solvent-based primer-sealer instead of latex paint here to prevent any residual water contamination from interfering with the binding with the fresh paint layer. Latex is appropriate for use as a finish coater over priming, although it may bubble if put directly over past water damage. Allow the primer to dry completely before applying the finish wall paint.
Warning: Wear safety glasses when scraping as well as sanding above your head or on a ceiling. Excess joint compound should not be washed down the drain since it can harden in the pipes. Scrape it into a trash bag instead. It is safe to flush the small quantity that remains on your tools.
Tips to Repair Water Damaged Ceiling Plaster
Before repairing the ceiling, repair the cause of the leak. Do not sand between joint compound coats. If there are any ridges or lumps, use the drywall knife to remove them. Sanding in between layers will most likely result in a wavy, uneven surface. Use a plaster patch or Plaster of Paris for a more durable repair. It is important to note that, unlike joint compounds, it is far more difficult to sand smooth.
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