How to Repair Cracked Emulsion Paint on Walls – A Simple Guide

How to Repair Cracked or Crazed Emulsion Paint on Walls

Cracked emulsion paint on walls is a common issue that can make any space look less appealing. Whether you’re dealing with hairline cracks or larger peeling patches, it’s easy to fix the problem if you follow the right steps. In this guide, we’ll show you how to repair cracked or crazed emulsion paint on walls and provide tips on how to prevent it from happening again. Plus, we’ll recommend the best products for a smooth, durable finish.

Why Does Emulsion Paint Crack on Walls?

Understanding why emulsion paint cracks is the first step in fixing it properly. Some common causes include:

  • Moisture – Dampness in the walls can prevent the paint from adhering properly, causing the paint to lift and crack over time. Trapped moisture weakens the paint film, leading to peeling.
  • Poor Surface Preparation – If walls are not cleaned or primed before painting, dirt, grease, or remnants of old paint can interfere with the new layers, preventing proper adhesion and leading to cracks.
  • Temperature Changes – As walls expand and contract with temperature fluctuations, the paint film can crack under the pressure. If the paint is applied too thickly or the surface isn’t prepped correctly, this movement can result in cracking.
  • Thick Coats of Paint – Applying too much paint can lead to cracks as it dries. Thick layers take longer to cure, and as they dry, the top layer may harden before the underlying layer, causing tension that results in cracks.
  • Painting On Top of Silk Emulsions – Crazing happens when vinyl or contract matt emulsions are applied over shiny surfaces, causing cracks due to expansion and contraction. Low-quality matt paints are more prone to this as they lack flexibility.

By addressing these issues, you can avoid future cracking and achieve a long-lasting finish.

Tools & Materials You’ll Need

Before you start repairing cracked emulsion paint on walls, gather these essential tools and materials:

  • Paint scraper – To remove any loose or peeling paint.
  • Sandpaper – For smoothing rough areas (medium and fine grit).
  • Flexible filler – Ideal for filling deep cracks.
  • Microfibre cloth – To clean off dust before repainting.
  • Primer or sealer – Helps the new paint adhere better.
  • High-quality emulsion paint – For a smooth, durable finish.
  • Paint Rollers and brushes – For applying the paint evenly.

Step-by-Step: How to Repair Cracked Emulsion Paint on Walls

Step 1: Assess the Damage

Check whether the cracks are hairline cracks or deeper fractures. If the wall is damp, take steps to fix the moisture problem before painting.

Step 2: Prepare the Surface

Use a paint scraper to remove any loose or flaking paint. Sand the area lightly to smooth out rough patches - avoid oversanding as this can cause the surface to expand, leading to more issues. Wipe away any dust with a microfibre cloth.

Step 3: Fill the Cracks

For deep cracks, apply a flexible filler and smooth it with the scraper. Allow the filler to dry completely before gently sanding it for a smooth, even finish.

Step 4: Apply Primer or Sealer

To prevent further cracking, apply a primer or sealer such as Zinsser Peel Stop or Zinsser Gardz. This acts as a barrier between your cracked wall and new matt paint, filling in hairline cracks. Let it dry fully - ideally for a full day - before repainting.

Step 5: Repaint the Wall

Apply two thin coats of emulsion paint rather than one thick coat. Thin coats dry more evenly and reduce the risk of cracking. Allow each coat to dry completely before applying the next, using a roller for even coverage and a brush for edges and corners.

Best Paints & Primers to Prevent Future Cracking

1. Zinsser Peel Stop

Seals cracked or peeling surfaces and improves paint adhesion acting as a barrier.

2. Zinsser Gardz

A clear sealer that improves adhesion on porous surfaces and helps to block moisture penetration.

3. Johnstone’s Trade Covaplus Vinyl Matt

This durable, high-opacity emulsion resists cracking and provides a professional finish.

4. Dulux Trade Supermatt

Ideal for new plaster, this paint helps reduce shrinkage cracks and offers excellent coverage.

5. Crown Trade Clean Extreme

A durable, polymer-rich paint available in finishes like Scrubbable and Anti-Mould, ideal for high-traffic or moisture-prone areas.

Top Tips to Prevent Future Cracking

  • Mist Coat Fresh Plaster: Applying a mist coat to fresh plaster helps the paint bond better, ensuring a smoother finish and preventing cracking. This creates a breathable base layer for the topcoat.
  • Ensure Walls Are Dry: Moisture can lead to paint cracking over time. Make sure the walls are completely dry before painting to avoid any issues caused by trapped moisture beneath the paint.
  • Avoid Extreme Temperatures: Paint dries best in moderate conditions. Extreme heat or cold can cause the paint to dry too quickly or unevenly, leading to cracks. Aim to paint in a temperature range of 10-20°C for the best results.
  • Use Flexible, High-Quality Paints: Opt for paints that are designed to be flexible and durable. High-quality paints, such as soft sheen, eggshell emulsion, or Zinsser Guardz, provide better adhesion and are less likely to crack as they expand and contract with temperature changes.
  • Create a Barrier Coat: Apply a flexible barrier coat with a primer between your shiny old paint and the new matt finish. This helps the matt paint bond properly while preventing moisture from passing through, ensuring longevity and preventing cracking.
  • Take Care When Preparing Surfaces: Proper surface prep is key. Only apply paint to surfaces that have been thoroughly cleaned, sanded, and primed. Never paint over cracked or peeling paint as this will lead to poor adhesion and more cracks.
  • Allow Each Coat to Dry Thoroughly: Don't rush the drying process. Always give each coat enough time to fully dry before applying the next. This prevents the layers from cracking as they settle.

Frequently Asked Questions

1. How can I prevent cracks in emulsion paint?

To prevent cracks in emulsion paint, make sure to properly prepare the surface by cleaning it and applying a good-quality primer. Use thin coats of paint instead of one thick coat, and ensure that the walls are dry and free from moisture before painting. It's also important to choose flexible, high-quality paints that can adapt to small surface movements.

 
2. Can I paint over cracked emulsion paint?

Yes, you can paint over cracked emulsion paint, but it's essential to repair the cracks first. Scrape off any loose paint, fill deep cracks with flexible filler, before applying a primer and fresh coats of paint. This will help ensure a smooth and long-lasting finish.

 
3. What type of filler should I use for cracks in emulsion paint?

For cracks in emulsion paint, use a flexible filler that can expand and contract with the wall. Products like polyfilla or any high-quality crack filler designed for wall surfaces are ideal. Be sure to smooth the filler before it dries, and sand it down to achieve a smooth, even surface.

4. What is the difference between a crack and crazing?

Crazing refers to a network of fine cracks that form on the surface layer of the paint, typically due to drying too quickly or temperature fluctuations. These cracks are shallow and don’t penetrate past the paint. In contrast, a crack is deeper and extends through the paint into the plaster or underlying surface. If the damage goes beyond the paint layer and into the wall, it's considered a crack, not just crazing.

 
5. How long should I wait before repainting after filling cracks?

After filling cracks, it's important to let the filler dry fully before repainting. This usually takes between 1 to 24 hours, depending on the depth of the crack and the type of filler used. Once dry, sand the filler to a smooth finish and ensure there is no dust left before applying primer and paint.

 
6. Can moisture cause emulsion paint to crack?

Yes, moisture is a common cause of cracks in emulsion paint. Damp walls prevent paint from adhering properly and can lead to peeling and cracking. It’s essential to address the source of the moisture, such as leaks or condensation, before repainting to prevent future issues.

 
7. What is the best type of paint for preventing cracks?

The best type of paint for preventing cracks is a high-quality emulsion paint that is flexible and designed for durability. Options like Johnstone’s Trade Covaplus Vinyl Matt or Crown Trade Clean Extreme are all excellent choices for their resistance to cracking and long-lasting finishes.

Conclusion

Now that you know how to repair cracked emulsion paint on walls, you can restore your walls to their best. Whether you're fixing hairline cracks or peeling areas, the right techniques and products will ensure a professional finish.

Explore our range of quality primers and paints to prevent cracking and keep your walls looking great for longer.