by michael daigle · 9 Jan 2024Have you ever looked around your room and noticed cracks or holes in your walls that just won't go away? Before you break out the paint, it's important to fix up any damage to your plaster. Repairing walls the right way before painting will help ensure an even, professional-looking finish and allow your new coat of paint to last longer. In this article, we'll walk you through the steps to patch up damaged plaster and smooth out imperfections. With a little time and patience, you'll have your walls ready for a fresh coat of paint in no time.
Assess the Damage: Identify Problem Areas Needing Repair
Once you've decided to freshen up your walls with a new coat of paint, the first step is identifying any areas of damaged plaster that need patching or repair.
Look for cracks, holes, or crumbling areas.
Inspect your walls closely, running your hands over the surface to feel for imperfections. Check corners and edges, around windows and doors, ceilings and baseboards. Even small cracks or holes can expand and worsen over time, so it's best to repair them before painting.
Assess water damage or leaks.
Look for stains, bowed or bulging areas, and soft or crumbling spots which indicate water damage. You'll need to eliminate the source of moisture before repairing and painting. Let the area dry completely.
Consider skim coating for uneven walls.
If your walls have bumps, ridges, or an uneven surface from previous paint jobs or wallpaper removal, applying a skim coat of plaster will create a smooth finish. Professional plasterers can re-plaster entire walls. For small areas, you can DIY with drywall compound and a wide putty knife or drywall blade.
Repair kits for small jobs.
For minor cracks, holes, and imperfections, a basic plaster repair kit with crack filler or spackle, a putty knife, sandpaper, and mesh tape can do the trick. Clean the area, apply filler with the putty knife, let dry, then sand smooth before painting.
With a little time and effort assessing and repairing any problem areas, your walls will provide the perfect blank canvas for your fresh coat of paint. And your room will look seamless and polished.
Prepare the Surface: Clean, Fill Holes, and Remove Loose Plaster
Once you've inspected the walls and identified any problem areas, it's time to get your hands dirty. Prepare the surface by cleaning, filling holes, and removing loose plaster so your new paint job lasts.
First, wipe down the walls to remove dirt and debris. Vacuum up any plaster dust and wash the walls with a damp cloth or sponge to get them squeaky clean.
Next, fill any cracks, holes, or dents. Use a putty knife or drywall knife to scrape out loose plaster around damaged areas. Clean out debris, then apply spackle, drywall compound, or plaster of Paris with a putty knife or drywall knife. Let it dry completely as directed, then sand smooth.
For loose plaster, carefully pry off any sections that are detached from the wall using a putty knife, then clean and fill the area underneath. If large sections (bigger than 6 inches) are damaged or cracking, it's best to remove them and re-plaster.
Once repairs are made and dry, lightly sand any rough spots. Wipe away dust with a tack cloth to ensure surfaces are clean before painting. Your walls are now ready for a fresh coat of your favorite color. With the proper prep work done, your new paint job will look professionally done and last for years.
Choose the Right Plaster for the Job
The type of plaster you choose depends on the level of damage. For minor cracks and holes, a lightweight spackle or patch compound will work well. For more significant damage that goes beyond surface level, you’ll need a heavier plaster.
Patching Compound
If you just have a few small cracks or holes, a patching compound is ideal. It’s easy to apply and dries quickly. Look for a lightweight compound that can be sanded smooth. Apply with a putty knife or drywall knife and let dry as directed. Lightly sand, then paint.
Joint Compound
For damage that exposes the wall behind the plaster, joint compound is a good choice. Also known as drywall mud, joint compound hardens as it dries. It may require a few applications to build it up and smooth it out. Joint compound typically dries in 1 to 2 days between coats. It can then be sanded to create an even surface before painting.
Plaster of Paris
Major damage like large holes, crumbling corners or plaster that’s pulling away from the wall will require a heftier solution like Plaster of Paris. This is a powder that hardens into a solid when mixed with water. Apply it with a putty knife, trowel or hawk and filling knife. Work in thin layers, letting each layer dry for 20 to 30 minutes. Smooth each layer as you go. Plaster of Paris sets quickly, so only mix as much as you can apply in 30 minutes. Once dry, sand any ridges before painting.
No matter which product you choose, proper preparation is key. Remove any loose plaster, wipe away dust and debris, and dampen the area to provide “tooth” for the new plaster to adhere to. With the right technique and patience, you can restore damaged plaster and end up with walls as smooth as new.
Mix the Plaster Properly for Best Results
Mixing plaster properly is key to achieving a smooth finish. The basic ingredients are plaster of Paris and water, but the ratio and technique are important.
Follow the Directions Carefully
Always follow the instructions on the product packaging for mixing proportions. As a general rule, use about 2 to 3 parts plaster to 1 part water. Add the plaster to the water slowly while stirring continuously.
Achieve the Right Consistency
The mixture should have a consistency like thick cake batter or sour cream. If it's too thin, it won't provide good coverage. If it's too thick, it will be difficult to spread and level. Add plaster or water 1 tablespoon at a time, stirring in between additions, until you reach the ideal consistency.
Avoid Lumps
Mix the plaster thoroughly to avoid lumps. An electric mixer or drill with a paddle attachment works well for this. Beat the mixture vigorously for at least 2 to 3 minutes until completely smooth. Any lumps left in the plaster will show through when dry.
Work Quickly
Plaster of Paris hardens quickly, usually within 30 minutes, so only mix as much as you can apply in that time. Do small test batches first to determine how much you need for each coat and section. Once it starts to thicken, it becomes difficult to spread and will not adhere as well.
Apply in Thin Layers
It's best to apply plaster in several thin layers, allowing each coat to dry completely between applications. Thinner coats are easier to spread smoothly and level. They also minimize cracking as the plaster dries. With proper mixing and application techniques, you'll have your walls ready for a fresh coat of paint in no time.
Apply Plaster Using Proper Technique for Smooth Finish
Once you’ve cleaned and primed the walls, it’s time to repair any damaged plaster before painting. For the best results, take your time and apply the plaster carefully using the proper technique.
Mix the Plaster
Follow the directions on the product packaging to mix the plaster compound. Add water slowly, stirring frequently, until it reaches a thick, creamy consistency. The plaster should be wet enough to spread easily but thick enough to cling to vertical surfaces.
Apply in Thin Layers
Apply the plaster with a putty knife, drywall knife, or spatula in thin, even layers. Roughly 1/8 to 1/4 of an inch thick is a good rule of thumb. Thinner layers are easier to smooth and less likely to crack as they dry. Let each layer dry completely, usually 2 to 3 hours, before applying additional layers.
Press and Smooth
As you apply each layer, use your tool to press the plaster firmly into the wall surface. Then, drag the edge of the tool over the plaster using light, even pressure to create a smooth finish. Wipe away any excess plaster from the surface surrounding the damaged area.
Lightly Sand Between Layers
Once a layer is dry, gently sand it with fine-grit sandpaper (around 220 grit) before applying the next coat. This will provide “tooth” for the new layer to grip onto. Wipe away dust with a tack cloth before continuing.
Feather Out the Edges
As you build up layers, use a light touch to feather out the edges of the plaster into the surrounding wall surface. This helps create an even, seamless transition between the patch and the existing wall.
With patience and the proper technique, you'll have your damaged plaster walls repaired and ready for a fresh coat of paint in no time. Take your time—the end result will be well worth the effort!
Let New Plaster Fully Cure Before Painting
Newly applied plaster needs time to dry completely to avoid problems when you paint over it. If you start painting too soon, you risk the paint not adhering properly or peeling and bubbling. For the best results, allow at least 30 to 90 days for new plaster to cure before painting, depending on the type of plaster.
- Gypsum plaster dries in 30 to 60 days. Gypsum, also known as drywall compound, is a lightweight material used to patch holes and seams in drywall. Allow at least a month for it to cure before painting.
- Lime plaster takes the longest to cure, around 60 to 90 days. Lime plaster is a traditional material made from lime, sand, and water. It needs ample time to carbonate as the lime chemically hardens. Rushing the curing time can lead to splotchy, uneven paint results.
- Cementitious plaster, made from cement, lime, and sand, cures in around 45 to 60 days. While cement hardens quickly, the lime in the mix needs additional time to fully cure. Patience is key!
To test if new plaster is ready for paint, gently press your fingernail into the surface. If it leaves an indentation, it's still too soft. You should not be able to scratch the plaster with your fingernail when fully cured. You can also use a moisture meter to check that the moisture content is below 15 percent, the level needed for most paints.
New plaster may look dry on the surface but still be damp underneath. Don't be tempted to speed up the curing time using heaters or fans, which can cause uneven drying and cracking. The best approach is to maintain normal indoor temperatures and relative humidity and allow the natural curing process to run its course. Your patience will pay off with a durable paint finish.
Sand and Prime Repaired Areas
Now that you’ve repaired any damaged plaster in the walls, it’s time to prepare them for painting. Sanding and priming the repaired areas will provide an even, smooth surface for the new paint to adhere to.
Sanding the Patches
Once the plaster has dried completely, gently sand the repaired patches to rough up the surface and smooth the edges. Use fine-grit sandpaper, around 220 grit, and sand in small circles. Wipe away dust with a tack cloth. This scuffing of the surface will give the primer and paint something to grip onto.
Applying Primer
Primer helps the new paint bond securely to the surface. For plaster walls, use an oil- or shellac-based primer. Apply at least one coat of primer to the entire wall, not just the patched areas. Focus on brushing or rolling primer onto the repaired patches to seal them. Let the primer dry as directed.
Inspect and Lightly Sand
Inspect the primed walls for any drips, splatters or uneven areas. Lightly sand them to create a uniform surface. Wipe away dust again with a tack cloth.
Caulk Cracks and Gaps (optional)
If there are any remaining hairline cracks between the plaster and trim or in the corners of the room, caulk them with a paintable latex caulk. Smooth the caulk with a wet finger before it dries. This step will prevent air leaks and ensure even coverage when you paint.
Final Wipe Down
Give the walls one final wipe down to remove any remaining dust before painting. Your walls are now prepped and ready for a fresh coat of paint. All your hard work repairing damage and prepping the surface will result in a smooth, professional-looking finish.
Sanding, priming and caulking are essential preparation steps when restoring damaged plaster walls. Put in the effort to do it right and your walls will be ready for whatever color you choose!
Check Moisture Levels Before Painting
Once you’ve repaired any cracks or holes in the plaster, it’s important to check the moisture levels before painting. Too much moisture trapped behind the new paint coat could lead to bubbling, peeling, and other issues down the road.
Use a moisture meter
Invest in a reliable moisture meter to test multiple areas of the plaster. For most paints, the moisture content should be below 15% before painting. Higher than that and you’ll want to hold off and re-test in a few days.
Check for damp spots
Look for any visible signs of dampness or water damage. Dark spots, warped areas, or plaster that feels soft or spongy to the touch could indicate excess moisture that needs to be addressed. You may need to call in a professional to determine the source and make necessary repairs before painting.
Improve ventilation
Run an exhaust fan, open windows, and use a dehumidifier to improve airflow and reduce extra moisture in the room. This is especially important for plaster walls in basements, attics or any space that may be prone to condensation buildup.
Allow extra drying time
If the plaster has been subjected to water damage or leakage, it can take weeks or even months to fully dry out. Be patient and continue checking moisture levels regularly. It’s best to postpone painting until the plaster has had ample time to dry to avoid issues with your new paint finish.
Consider a primer
Applying a coat of primer designed for high-moisture surfaces can help block excess moisture and provide a sound base for your paint. Check with your paint supplier for recommendations on the best types of primer and paint to use in high-moisture areas. The extra investment in proper preparation will pay off with a durable, long-lasting finish.
By checking moisture levels thoroughly before painting damaged or repaired plaster walls and ceilings, you’ll avoid frustration later on and end up with results that look professional and stand the test of time. The key is patience and taking the necessary steps to ensure your plaster is in the optimal condition to accept the new paint.
Paint Restored Walls Using Quality Paint and Supplies
Once your walls are repaired and ready, it’s time to paint. For the best results, use high quality paint and supplies.
Paint
Choose a premium latex or acrylic paint. These provide great coverage in fewer coats and a durable, washable finish. For plaster walls, a primer-sealer followed by two coats of paint is typically needed. An eggshell or satin sheen is ideal for most rooms. Flat paint hides imperfections well but stains easily. Glossy paint is too shiny for plaster.
Brushes and rollers
Use a brush to paint edges and corners, then roll the walls. A 2- to 3-inch angled sash brush is versatile. For rolling, choose a 3/8-inch nap roller cover for smooth plaster and a 1/2-inch nap for textured. Load the roller fully for the first coat.
Paint trays and liners
A paint tray with a liner or disposable tray will make the job neater. Pour in only as much paint as needed for the area you’re working on.
Painters tape
Apply painter's tape for sharp edges and trim. Press firmly so paint won’t bleed underneath. Remove tape as soon as you're done painting the area.
Paint shield and drop cloths
A paint shield protects doorways and floors. Canvas drop cloths absorb drips better than plastic.
Ladder and lighting
A sturdy ladder provides safe access. Bright lighting shows flaws and uneven coverage, so paint during the day or use proper task lighting.
Ventilation
Keep windows open and use fans for good airflow and to minimize fumes.
With the proper tools and technique, your fresh coat of paint will make those repaired walls look as good as new. Take your time—patience and precision pay off with professional-looking results.
Final Thoughts
So there you have it, the essential steps to repair damaged plaster before painting your walls. While it may seem like a tedious process, taking the time to do it right will ensure your fresh coat of paint looks smooth and professional. Patching cracks, filling holes, and sanding imperfections will provide the perfect blank canvas for your new wall color. With some patience and elbow grease, you'll have walls ready for a makeover in no time. Time to pick out those paint swatches - you've earned it! Go ahead and give your walls a face-lift they deserve. Your newly refreshed space will make all that hard work worthwhile.