Cracks appearing in your walls, ceilings or external brickwork can be worrying. One of the most common questions we hear from homeowners is: “Why is my house cracking?”
The answer is not always straightforward.
Some cracks are minor and associated with normal movement of building materials, while others may indicate foundation movement, changing soil conditions, poor drainage or other building defects.
If you own or are considering purchasing a property in Melbourne, understanding the possible cause of cracking is important before simply filling the cracks and repainting.
What Causes Cracks in Houses?
Houses are not completely rigid structures. They are affected by changes in temperature, moisture, soil conditions and the performance of their footings and foundations.
Minor movement can occur without causing significant structural concerns. However, when movement becomes excessive or uneven, visible cracking may develop.
The location, direction, width and pattern of a crack can provide important information about what may be occurring.
1. Reactive Clay Soils and Foundation Movement
One of the most important causes of house cracking in Melbourne is movement in the soil beneath and around the foundations.
Many Melbourne suburbs contain reactive clay soils. These soils can expand when they absorb moisture and shrink when they dry out.
During prolonged hot and dry weather, moisture can be lost from the soil surrounding a house, causing it to contract. Following periods of significant rainfall, the same soil may absorb moisture and expand.
If these changes occur unevenly beneath a building, sections of the footings or concrete slab can move differently from others.
This movement may result in cracking to internal plaster walls, ceilings and external brickwork.
2. Poor Drainage Around Your House
Drainage problems can contribute significantly to foundation movement.
Blocked gutters, leaking downpipes, overflowing stormwater systems, poorly graded paving and garden beds against external walls can allow excessive moisture to accumulate close to the foundations.
We regularly find properties where surface water is being directed towards the house instead of away from it.
This can create substantially different moisture conditions around various sections of the foundations.
When investigating house cracking, it is therefore important to inspect not only the cracks but also the surrounding drainage, paving, ground levels, gutters and downpipes.
3. Trees and Large Vegetation
Trees can also influence soil moisture conditions around a house.
Large established trees may draw substantial amounts of moisture from surrounding soil. During extended dry periods, this can contribute to additional drying and shrinkage of reactive clay soils.
However, the presence of a tree near a house does not automatically mean it is responsible for cracking.
Tree species, size, distance from the building, soil classification, drainage conditions and foundation design all need to be considered.
Removing a large tree without appropriate investigation may also alter the moisture conditions around the foundations.
4. Cracks in External Brickwork
Cracking to brickwork can take several forms.
Minor cracks within mortar joints may not necessarily indicate a serious problem. However, stepped cracking through brickwork, substantial vertical or diagonal cracking, or cracks extending from window and door openings may require further investigation.
Cracking can also occur around steel lintels above windows and doors.
Expansion and articulation joints are incorporated into masonry construction to accommodate movement. Where these joints are inadequate, incorrectly located or filled with rigid materials, cracking may develop as the building moves.
5. Cracks in Internal Walls and Ceilings
Hairline cracking to plasterboard joints and cornices is relatively common, particularly as building materials expand, contract and settle.
However, cracking becomes more concerning when other signs of building movement are present.
These may include:
- Doors suddenly binding or failing to close correctly
- Windows becoming difficult to operate
- Gaps developing around skirting boards
- Separation between walls and ceilings
- Uneven or noticeably sloping floors
- Diagonal cracks extending from windows or doors
- Corresponding cracks internally and externally
- Cracks that continually return after being repaired
The overall pattern of movement is often more important than one isolated crack.
6. Water Leaks and Moisture Damage
Not every wall or ceiling crack is caused by foundation movement.
Roof leaks, plumbing leaks, failed waterproofing and prolonged moisture exposure can affect timber framing and other building materials.
Timber can expand when exposed to moisture and shrink as it dries. Prolonged moisture exposure may also cause deterioration.
For this reason, simply patching a crack without determining its underlying cause may only provide a temporary cosmetic repair.
Should I Be Worried About Cracks in My House?
Not every crack represents a major structural defect.
However, cracking should not automatically be dismissed as normal settlement either.
An experienced building inspector will consider the location, direction, pattern and extent of the cracking, together with other evidence throughout the property.
The inspection should also consider external drainage, soil conditions, ground levels, vegetation, foundation movement and whether doors, windows or floors show evidence of distortion.
Where appropriate, cracks may be monitored to determine whether movement is continuing.
Don’t Just Patch and Paint House Cracks
Repeatedly filling and painting cracks without investigating the cause can hide the symptom without correcting the problem.
If movement continues, the cracks are likely to return.
This is particularly important when purchasing a property. Fresh paint and recent patching can make it difficult for buyers to appreciate the history or extent of previous cracking.
A professional building inspection in Melbourne can help identify visible evidence of movement and provide a better understanding of the condition of the property before you make important decisions.
Need a Building Inspection in Melbourne?
If you have discovered cracking in your home or are considering purchasing a property showing signs of movement, arrange a professional building inspection.
We inspect properties throughout Melbourne and assess visible cracking together with the surrounding building and site conditions to help determine the likely cause and whether further investigation is recommended.
Remember: the crack itself is often only the symptom. The important question is what is causing the building to move.
