How To Fix Cracks In Walls

Cracks in walls can not only ruin the aesthetic appeal of your house, but also pose risks to the safety and integrity of your home. 

If you spot any cracks in your walls, fix them on time, before they lead to significant issues. Ignoring them can result in penetrating damp, which can cause mould growth, structural damage, and other costly repairs. 

To maintain the integrity of your home, it’s essential to fix wall cracks as soon as they appear. Wall cracks can also indicate underlying issues that may worsen over time. 

For example, cracks caused by foundational shifts can lead to severe structural problems. If you repair the cracks early, you can prevent minor issues from escalating into major repairs, saving you both time and money.

This comprehensive guide covers the causes of wall cracks, the different types of cracks, and their severity. It provides detailed, step-by-step instructions for repairing both internal and external wall cracks. Additionally, we’ll discuss when it’s necessary to call a professional for assistance.

What causes cracks in walls? 

It can be extremely useful to understand the underlying cause of cracks in walls, as this can help you prevent them from happening again and ensure your home is kept in the best condition.

The most common causes of wall cracks are:

• Weather Conditions

The UK has high humidity levels and frequent rainfall, which can significantly contribute to forming cracks in your walls. When temperatures fluctuate, the expansion and contraction of the building materials can also make small cracks appear. 

• Ground Movement and Soil Settling

Natural ground movement, soil erosion, and settling can all cause foundation shifts, leading to cracks in walls. This is particularly common in areas with clay-rich soils that expand and contract significantly when moisture levels change.

• House Settling

Over time, most houses settle to some degree. This natural process can result in minor cracks, particularly in new homes as they adjust to their foundations.

• Poor Construction Practices

Inadequate construction techniques, such as poor curing of concrete or using low-quality materials, can weaken the structure and lead to cracking.

• Structural Stress or Damage

Additional stress from renovations, additions, or even nearby construction work can cause cracks to appear in walls. Structural damage from earthquakes, and heavy winds, can also contribute to cracks in walls.

• Water leaks

When water seeps into walls due to leaks, it can weaken the building materials, leading to cracks over time.

Types and severity of cracks in walls 

Cracks in walls can widely vary in appearance, and some of them can be more severe than others, leading to structure damage and expensive repairs. To effectively determine the appropriate method to fix your walls’ cracks, you need to identify the type of crack. Some of them are:

1. Hairline Cracks: These are small, superficial cracks that often occur in the plaster or paint layer of the wall. They are usually caused by minor settling or drying of plaster and are not something you should be concerned about.
2. Vertical Cracks: Vertical cracks are commonly caused by the normal settling of the house and are generally less serious. However, if a vertical crack widens significantly, it may indicate a more severe issue.
3. Horizontal Cracks: Horizontal cracks can be a sign of serious structural problems, such as foundation issues or significant soil pressure. These cracks require immediate professional assessment.
4. Diagonal Cracks: Diagonal cracks are often caused by differential settlement of the foundation. They can vary in severity.

Step-by-step guide to fixing internal wall cracks

Repairing internal wall cracks is a straightforward process, but it requires careful preparation and the right tools. Whether you’re dealing with minor hairline cracks or more severe ones, our guide can help you get a professional finish and maintain the structural integrity of your home.

1. Identify the Crack

The first step in fixing internal wall cracks is to identify and assess the crack. Have a look at the crack and examine its size and type to determine the appropriate method of repair. Pay attention to any changes in the crack over time, as this could indicate ongoing structural issues that might need professional attention.

2. Prepare the Necessary Tools 

Make sure you have the necessary tools. Having these on hand will make the process easier and ensure you achieve the best results. You will need:

• Putty knife or penknife
• Hammer
• Scraper
• Sandpaper
• Plaster or filler
• Paint and primer
• Dust mask and safety goggles

3. Prepare the Area

Before you start to fix the crack, clean the area thoroughly using a brush and remove any loose debris or dust. This will give you better results by ensuring that the filler adheres properly to the surface. 

Next, use a utility knife to slightly widen the crack. This will help the filler bond more effectively. Make sure to wear a dust mask and safety goggles during this step to protect yourself from dust and debris getting in your eyes or nose.

4. How to Fix Small Cracks

For small cracks, follow these steps:

• Apply a filler or plaster into the crack using a putty knife. Press firmly to ensure the filler gets into the crack, filling it completely.
• Smooth the surface of the filler with the putty knife, removing any excess material. This creates a level surface that blends seamlessly with the surrounding wall.
• Allow the filler to dry according to the manufacturer’s instructions. Drying times can vary, so make sure to follow the guidelines provided.
• Once dry, sand the area with fine-grit sandpaper to achieve a smooth finish.
• Apply a coat of primer to the repaired area to prepare it for painting. Once the primer is dry, paint over the area to match the surrounding wall.

5. How to Fix Large Cracks

Larger cracks require more care and experience:

• Use a chisel and hammer to widen the crack and remove any loose material. This step creates a solid base for the filler, ensuring a durable repair.
• Apply a patching compound in layers, allowing each layer to dry before adding the next. Building up the compound in layers ensures a strong and long-lasting repair.
• Once the compound is fully dry, sand the area smooth. This will help achieve a seamless finish.
• Prime and paint the repaired area to match the rest of the wall. Priming ensures the paint adheres well and provides a uniform appearance.

If you follow these steps correctly and use high-quality materials, you can help to effectively repair your wall cracks and prevent further damage. Maintaining your walls and repairing any cracks that might appear on time, can keep your house in good condition and ensure you don’t get any structural damage. 

In case the cracks are too big and beyond your capabilities, or you notice significant structural concerns, it’s always best to consult a professional for advice and assistance.

Step-by-step guide to fixing external wall cracks 

Repairing external wall cracks involves additional considerations due to exposure to weather elements. Here’s how to address them effectively:

1. Prepare the Tools Needed

For external repairs, you’ll also need:

• Exterior grade sealant
• Masonry patching compound
• Waterproofing solution
• Trowel
• Brush

2. Prepare the Area

Start by cleaning the crack area thoroughly. Remove any loose debris with a brush. To widen the crack slightly, use a trowel. This will ensure that the filler adheres properly. Always wear a dust mask and safety goggles to protect yourself.

3. Fix Small Cracks

• Apply an exterior grade sealant into the crack using a caulking gun. Press firmly to ensure the sealant fills the crack completely.
• Smooth the sealant with a scraper, removing any excess material.
• Allow the sealant to dry.

4. Fix Large Cracks

• Fill the crack with a masonry patching compound. Apply the compound in layers, allowing each layer to dry before adding the next.
• Once the compound is fully dry, sand the area smooth.
• Apply a waterproofing solution to prevent future water penetration.
• Finish by painting the repaired area to match the surrounding wall.

How to prevent cracks in my walls?

Preventing wall cracks in the UK requires proactive measures due to the region’s weather conditions and soil types. Some of the things you can do to prevent cracks are:

1. Control Moisture Levels:

• Ensure proper drainage to direct water away from the foundation.
• Use dehumidifiers in humid areas and maintain good ventilation to prevent dampness. In particular, look out for bathroom condensation and mould.

2. Maintain a Stable Foundation:

• Monitor the soil moisture around your home, especially in clay-rich areas.
• Plant trees and shrubs at a safe distance from your house to prevent root damage.

3. Use High-Quality Materials:

• Opt for durable plaster, exterior-grade paint, and flexible sealants to reduce cracking risks.

4. Regular Home Maintenance:

• Inspect walls regularly for early signs of cracks and repair minor issues promptly.
• Keep gutters and roofs well-maintained to prevent water damage.

5. Control Temperature Fluctuations:

• Insulate your home properly to maintain consistent indoor temperatures.
• Avoid rapid heating or cooling that can cause building materials to expand and contract.

When to Call a Professional

While many cracks can be repaired with DIY methods, there are situations where professional help is necessary. If left untreated, your wall cracks might get bigger and cause serious structural damage. Call Allerton Damp if:

• You notice significant structural damage, such as sagging floors, bowing walls, or large cracks.
• The cracks are widening or appearing in multiple areas. This could indicate a serious underlying issue that requires expert attention.
• The repair work is beyond your DIY skills or comfort level, it’s best to hire a professional to ensure the job is done correctly.
• You’re unsure about the extent of the damage or the appropriate repair method, consult a professional like ourselves for advice and assistance.

If you’re worried about damp or timber-related issues in your home, we can provide a free property survey by an experienced Surveyor.