Fixing Cracks in Plaster Walls: A DIY Guide for Homeowners

Cracks in plaster walls are a shared challenge for many homeowners across South Africa. Whether you reside at the coast or in the highveld, temperature fluctuations, moisture, and foundation movement can all contribute to the development of these cracks over time. 

The good news? You’re not alone, and with some time, materials, and basic DIY knowledge, you can often repair these cracks.

Here’s a simple, step-by-step guide to help you fix plaster wall cracks and restore your walls to their former glory. You’ll be surprised at how simple it can be!

Step 1: Assess the Crack

Before diving into repairs, inspect the crack carefully. Hairline cracks are generally harmless and cosmetic, but wider cracks (wider than 5mm) could indicate structural movement. If the crack reappears after repairs or grows over time, it may be best to consult a structural engineer or builder for advice.

Read our blog: 5 Tips for Hiring a Builder

Step 2: Gather Your Tools and Materials

To get started, you’ll need:

• Plaster crack filler or jointing compound
• A putty knife or scraper
• Sandpaper (medium and fine grit)
• A paintbrush or a damp cloth
• Primer or bonding liquid
• Paint to match the wall

Most of these supplies are readily available at local hardware stores such as Builders Warehouse or Leroy Merlin, so you can easily gather what you need to start.

Step 3: Clean and Prep the Area

Use a utility knife or scraper to widen the crack slightly and remove any loose plaster. This might seem counterintuitive, but it helps the filler bond properly. Clean the area with a brush or a damp cloth to remove dust and debris. For best results, apply a bonding liquid to the exposed plaster and let it dry before moving on.

Step 4: Apply the Filler

Using your putty knife, fill the crack with plaster filler or joint compound. Push the filler deep into the crack, ensuring there are no air pockets. Smooth it out and feather the edges to blend with the surrounding wall. Let it dry completely. Drying times will vary depending on the product and weather conditions, especially in humid or coastal areas.

Step 5: Sand and Smooth

Once the filler is dry, sand the area with medium-grit sandpaper, followed by fine-grit sandpaper for a smoother finish. Be sure to remove any dust afterwards with a clean cloth or brush.

Step 6: Prime and Paint

Apply a coat of primer over the repaired area to seal it and improve paint adhesion. Once dry, repaint the wall using matching paint. Consider repainting the entire wall for large or prominent areas to ensure a consistent finish.

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Final Tips

• If you live in an area prone to damp, like the Garden Route, consider using a moisture-resistant filler.
• Consider using a flexible filler to handle minor wall movement for recurring cracks.
• Regularly check for signs of structural movement or damp to prevent future issues.

Fixing cracks in plaster walls can be a satisfying and straightforward weekend project with a bit of effort and the right approach. Not only does it improve the look of your home, but it also helps maintain its value and integrity over time.