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Cracked walls
What is a Wall Crack?
A wall crack is a visible break or fissure that appears on the surface of a wall, which can occur in various building materials such as drywall, plaster, concrete, or brick.
These cracks can vary in size, shape, and depth and may appear in different locations, such as near windows, doors, corners, or along the middle of the wall.
Wall cracks can be caused by various factors, ranging from minor settling of the building to more serious structural or foundation issues. They can be classified as cosmetic (surface-level issues) or structural (indicating underlying problems that may affect the stability of the building).
Cracks in the walls of your home can be concerning, but not all cracks are signs of serious structural problems. Knowing how to identify the different types of cracks and how to assess their severity will help you determine whether you need to act or simply monitor the issue.
Types of Wall Cracks
Hairline Cracks
Appearance: Very thin, often no more than 1mm wide.
Causes: Minor settling of the house or shrinkage of materials as they dry out (e.g., plaster, drywall, or concrete).
Assessment: Typically, cosmetic and not a cause for concern. Monitor for any changes in width or length.
Vertical Cracks
Appearance: Straight lines running up or down a wall, often appearing in drywall, plaster, or brick.
Causes: Can occur due to the natural settling of the house or due to thermal expansion and contraction of materials.
Assessment: If small and stable, it’s often not a problem. However, if the crack widens over time or causes the wall to bow, it could indicate a deeper issue, like foundation settling.
Horizontal Cracks
Appearance: Cracks running horizontally along the wall, often seen in masonry or concrete walls.
Causes: These cracks are more serious than vertical ones and can indicate structural issues such as foundation settlement, water pressure against the wall, or soil movement.
Assessment: If you notice a horizontal crack, especially if it appears in the basement or foundation, have it evaluated by a professional as it may be a sign of structural instability.
Diagonal Cracks
Appearance: Cracks that run at an angle, often seen near the corners of doors or windows.
Causes: These cracks are often due to foundation movement, changes in moisture levels, or the settling of the structure.
Assessment: Minor diagonal cracks may be normal, but significant or growing cracks should be investigated by a structural engineer.
Step Cracks
Appearance: These cracks follow the mortar lines of brick or masonry, creating a “stair-step” pattern.
Causes: Step cracks are often caused by foundation settlement, soil expansion, or water infiltration.
Assessment: If step cracks are wide or continue to grow, it’s important to have the foundation checked.
Shrinkage Cracks
Appearance: These are small, usually hairline cracks that develop as materials like plaster, drywall, or concrete dry and shrink.
Causes: Natural shrinkage of building materials as they cure or dry.
Assessment: These cracks are typically harmless but should be monitored to ensure they don’t develop into larger cracks.
What Causes Walls to Crack?
Walls can crack for several reasons, ranging from natural settling of the house to more serious structural or environmental issues.
Understanding the underlying causes of wall cracks can help determine whether they’re minor, cosmetic, or indicative of a more significant problem. Here are the main factors that cause walls to crack:
1. Foundation Movement
Settling: As a house ages, its foundation can settle into the ground, which can lead to the cracking of walls. This is especially true if the soil beneath the foundation shifts or compresses.
Foundation Shifting: Changes in soil conditions (e.g., moisture variations, frost heaving, or soil erosion) can cause the foundation to move unevenly, leading to cracks in walls. This is more common in homes with basements or crawl spaces.
Foundation Problems: Issues such as poor construction, inadequate materials, or water damage to the foundation can lead to significant cracks in walls. Horizontal cracks, for example, may suggest serious foundation instability.
2. Moisture and Humidity Changes
Water Infiltration: Leaks from pipes, roofs, or exterior walls can introduce moisture into the building materials, weakening them and causing them to crack. Damp conditions can also lead to the expansion of certain materials like plaster, causing cracks.
Drying and Shrinkage: In drywall, plaster, or concrete walls, moisture content can affect how materials dry out. As these materials shrink while drying, they may develop cracks. This is especially common in new constructions where materials are still curing.
Seasonal Changes: Seasonal fluctuations in humidity and temperature can cause walls and foundations to expand and contract, leading to cracks. For example, during summer, dry conditions can cause wood framing to shrink, while moisture can cause it to swell in the winter.
Foundation Problems: Issues such as poor construction, inadequate materials, or water damage to the foundation can lead to significant cracks in walls. Horizontal cracks, for example, may suggest serious foundation instability.
3. Temperature Changes
Thermal Expansion and Contraction: Materials like wood, concrete, and brick expand and contract with temperature fluctuations. If the change in temperature is significant, this movement can lead to the formation of cracks.
Hot or Cold Weather: Extreme temperatures, particularly rapid heating or cooling, can stress materials and cause them to crack, especially if the wall was previously weakened.
4. Soil Shifting
Soil Movement: The soil beneath and around a house can shift due to changes in moisture levels, freezing and thawing cycles, or earthquakes. Expansive soils (clay-rich soils that expand and contract with moisture) can cause foundation and wall cracks as they swell when wet and shrink when dry.
Poor Compaction: If the soil was poorly compacted during construction, it may settle unevenly, leading to cracks in the walls over time.
5. Building Settling
Natural Settling: New homes and buildings go through a settling phase, where the materials and the foundation adjust to the weight of the structure. This can result in minor cracks, which are typically harmless.
Uneven Settling: If the settling is uneven, it may cause shifts in the structure, leading to cracks in the walls. This is especially true in older homes, or those built on unstable ground.
6. Improper Construction or Material Defects
Poor Construction: Walls that are built with improper techniques or inadequate materials are more likely to crack. For example, if the mortar used in brick or masonry walls is of poor quality, or if drywall is installed incorrectly, cracks may appear more easily.
Defective Materials: Defective building materials, such as low-quality plaster, drywall, or concrete, can crack more easily. Manufacturing defects, such as air bubbles in plaster or concrete, can cause weaknesses in walls that lead to cracking.
7. Vibration or Structural Stress
Heavy Loads: If there is excessive weight placed on a wall (such as large furniture or structural elements), it may cause stress on the materials and result in cracks.
Nearby Construction or Traffic: Vibrations from nearby construction, heavy traffic, or even nearby machinery can put pressure on walls, leading to cracking over time.
8. Pest Infestation
Termites and Other Pests: In some cases, pests like termites or carpenter ants can damage the structural integrity of the walls. The tunneling they create within the wall can weaken materials, leading to cracks or even collapsing sections.
9. Age of the Building
Natural Aging: As buildings age, the materials used to construct the walls may degrade or lose their original strength. The structure may shift slightly or materials may become brittle, causing cracks over time.
Settling Over Time: Even in older homes, settling continues to occur gradually, which may lead to minor cracks that develop slowly but steadily.
10. Overloading or Expansion
Overloading a Wall: If a wall is subjected to excessive weight, such as a heavy shelf, large furniture, or an incorrectly placed load-bearing item, it can crack under pressure.
Expansion of Building Materials: Some materials, like concrete or plaster, can expand and contract due to changes in temperature, moisture, or curing. This movement can lead to cracks over time.
11. Earthquakes or Natural Disasters
Seismic Activity: Earthquakes or other natural disasters, like floods or landslides, can cause immediate and significant cracks in the walls of a structure. These can be wide, deep, and require urgent repair.
How to Assess Wall Cracks
- Measure the Width and Length
- Use a ruler or tape measure to track the crack’s size.
- Take measurements at different intervals to determine if the crack is stable or widening.
- Monitor the Crack Over Time
- Mark the crack’s ends with a pencil or tape and monitor it regularly (every few months).
- If the crack’s size remains consistent, it is likely benign. However, if it continues to grow or change, further investigation may be needed.
- Examine the Surrounding Area
- Check for other signs of structural damage, such as sagging ceilings, uneven floors, or doors/windows that no longer close properly. These could be signs of foundation or structural issues.
- Check for Moisture
- Moisture can exacerbate cracks, especially in foundations. Look for signs of water damage around the cracks, including dampness, mold, or peeling paint.
- If moisture is present, it may indicate water infiltration, which could cause further damage over time.
Start measuring wall cracks from the convenience of your home.
If you notice wall cracks around your home that are:
Large cracks that start at windows, doorways or corners of buildings
Cracks wider than 5mm
Jagged, horizontal or vertical, zig-zagged, stepped in brickwork or follow mortar line
These characteristics may indicate weakness in your property’s foundation.
To help you discover if the cracks in walls around you home could be due to subsidence, we’ve developed this handy tool. Download our FREE crack gauge and start measuring and monitoring the wall cracks around your home now!
When Should I Worry About Cracks ?
While minor cracks can often be monitored and repaired by homeowners, there are situations when it’s essential to contact a professional:
Large or Growing Cracks: If the crack is wide (greater than 1/8th inch) or continues to expand, it may signal a more serious structural issue.
Signs of Foundation Problems: Horizontal cracks, diagonal cracks near windows/doors, or step cracks in masonry often point to issues with the foundation that require professional inspection.
Sagging Floors or Walls: If you notice significant bowing, sloping, or cracking in the floor or walls, it may be an indication of underlying structural problems.
Water Damage: Cracks accompanied by dampness, mould, or mildew often require a professional assessment to prevent long-term damage.
Video
Residential External Cracked Wall
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Repairing Wall Cracks
Before & After Treatment
Houses that need to be re-levelled often develop cracks in walls, which can occur internally and externally.
Minor Cracks: For small, hairline cracks, simple patching with caulk, plaster, or joint compound is sufficient. Sand the surface and repaint as necessary.
Larger Cracks: For more significant cracks, you may need to use a stronger filler, such as epoxy or a specialised wall repair kit. Some cracks may need reinforcement with drywall tape before patching.
Foundation Cracks: If the crack is in the foundation, it’s critical to repair it to avoid further damage. Foundation crack repair might involve sealing with epoxy injections or installing wall anchors.
Not all wall cracks are a cause for concern, but homeowners must be vigilant.
Regularly inspect your walls, measure any cracks, and monitor them over time. If you notice significant changes or suspect structural issues, don’t hesitate to consult with a professional for an evaluation. Identifying cracks early can help you make timely repairs and prevent more costly damage down the road.
FAQs
Are cracks in the wall normal?
Yes, cracks in walls are relatively normal especially in older homes as they settle over time. Hairline cracks are often not cause for concern, but larger cracks (over 3mm) may indicate more serious structural problems.
Can you paint over cracks?
You can definitely paint over cracks after having them properly filled, this will ensure you get a seamless finish.
How do you fix structural cracks in walls?
If you’re concerned that the cracks you’re seeing could be the result of foundation movement, it’s best to get in contact with us. See our wall crack repair page to learn more about our process and get a free quote.
When should I worry about cracks in walls?
You should be concerned about cracking when they are bigger than 3mm in width, become wider over time, or are accompanied by other structural issues such as sticking doors and windows or uneven floors.
Horizontal cracks, stepped cracks, or cracks near openings are other types of cracking which may indicate significant structural problems that require investigating.
How to know if a crack is structural?
A crack is likely structural if they are wider than 3mm, appear in different patterns like horizontal or stepped patterns (see our examples above), and accompanied by other signs such as bulging walls, sticking doors and windows, or gaps at wall joints. If a crack continues to grow or reappears after repair, we recommend a professional evaluation.
Are cracks in the wall safe?
Not all wall cracks are unsafe. Hairline and minor vertical cracks are usually harmless and can be repaired quite easily.
However, larger cracks may indicate structural issues that could compromise the safety of your home, so we highly recommend these be inspected by a professional quickly. This is especially important if the crack is changing or showing progression over time.
When should I worry about plaster cracks in Australia?
Whether you find cracks in your plaster or brickwork, the criteria to assessing their severity is the same;
- Exceed 3mm in width
- Show signs of progression over time
- Form patterns like horizontal or stepped cracks
- Reappear after being repaired
- Are accompanied by other structural issues
Can you just paint over cracks in plaster?
Yes, you can paint over small hairline cracks after properly filling them with a suitable filler. However, we don’t recommend this for larger or structural cracks without addressing the underlying cause, as the problem may likely get worse over time, and will more than likely reappear
Mainmark also provide the following in Australia: wall crack repairs, sinking floor repair, Concrete slab repair, sinking foundation repair, underpinning, ground improvement, re-levelling, subsidence repair, void filling and slab lifting
Features & Benefits
Mainmark’s Solutions & Technologies
Fast
Our technologies have fast curing times and treated areas can be used immediately or without the delays compared to traditional repair methods.
Environmentally Inert
Our technologies use an inert material that is non-toxic and does not leach into the environment or affect the treated area.
Non-Invasive
Our solutions are of surgical nature compared to traditional methods.
Cost-Effective
Compared to traditional methods, our solutions are more cost-effective, with minimal disruption to the area.
Get a quote
Arrange a site assessment in 3 simple steps:
Step 1
Submit your enquiry using our online form. Include a brief message about the type of foundation issues you are experiencing.
Step 2
Our friendly customer service team will be in touch to schedule a site assessment that suits you.
Step 3
One of the Mainmark experts will visit your home or property, assess the damage, and ascertain the likely cause. They will establish the approach needed, creating a plan specific to the needs of your building and provide you with a detailed quote.
