Stepped cracking in brickwork is one of the more noticeable signs of movement that we find during building inspections throughout Melbourne.
Unlike a straight vertical or horizontal crack, stepped cracking follows the mortar joints between bricks, producing a distinctive staircase-shaped pattern.
If you have discovered this type of cracking in your home or in a property you are considering purchasing, you may naturally be wondering:
The answer depends on the extent of the cracking, its location, whether it is getting worse and, most importantly, what is causing the building to move.
What Does Stepped Cracking Look Like?
Stepped cracking generally follows the horizontal and vertical mortar joints between bricks.
Instead of cracking directly through each brick, the crack travels along the mortar joints before moving vertically to the next joint, creating a series of steps.
The cracking may be very fine and difficult to notice, or it may be several millimetres wide with obvious separation between sections of brickwork.
Stepped cracks are commonly found near:
- Windows and doors
- Corners of buildings
- Extensions and additions
- Changes in foundation construction
- Areas affected by poor drainage
- Sections where differential foundation movement has occurred
The pattern of the cracking can provide useful information when investigating possible building movement.
What Causes Stepped Cracking in Brick Walls?
One of the common causes is differential movement of the foundations or footings.
Differential movement means that one section of a building has moved differently from another.
Brickwork is relatively rigid. When the foundations supporting a masonry wall move unevenly, stresses can develop within the wall.
Once the masonry can no longer accommodate those stresses, cracking may occur.
The result can be the characteristic staircase-shaped crack visible through the mortar joints.
Reactive Clay Soils and Melbourne Houses
Soil conditions are an important consideration when investigating stepped cracking.
Many areas of Melbourne contain reactive clay soils. These soils can change volume considerably as their moisture content changes.
During extended periods of dry weather, clay soils can lose moisture and shrink. During periods of substantial rainfall, the soil can absorb moisture and expand.
If these moisture changes are uneven around the house, different sections of the foundations may move by different amounts.
Over time, this movement can contribute to cracking in external brickwork and internal wall finishes.
Poor Drainage Can Contribute to Foundation Movement
When inspecting stepped cracking, we do not just look at the crack itself.
We also examine the conditions surrounding the property.
Poor drainage can result in excessive moisture being concentrated around one section of the foundations.
Common problems include blocked gutters, leaking downpipes, damaged stormwater systems, garden beds against external walls, poorly graded paving and surface water flowing towards the building.
For example, if a downpipe continually discharges water beside one corner of a house, the soil conditions around that section may be substantially different from the soil on the opposite side of the property.
Maintaining reasonably consistent moisture conditions around the foundations is therefore important.
Can Trees Cause Stepped Cracking?
Trees and large vegetation may also influence soil moisture levels.
Large trees can draw significant amounts of moisture from the ground, particularly during prolonged dry periods.
In reactive clay soil, this loss of moisture may contribute to soil shrinkage and movement.
However, seeing a tree near a cracked house does not automatically mean the tree caused the problem.
The tree’s size, species and distance from the house need to be considered together with the soil type, drainage conditions, foundation design and overall pattern of movement.
Is Stepped Cracking Always Structural?
No.
The presence of stepped cracking does not automatically mean a house has a major structural defect or requires extensive foundation repairs.
Some cracking may be associated with relatively minor or historic movement that has stabilised.
The important issue is determining whether the movement appears to be minor and stable or significant and ongoing.
A professional building inspection considers the crack in conjunction with the rest of the property rather than reaching a conclusion based solely on its width.
What Other Signs Should I Look For?
Stepped cracking becomes more concerning when other evidence of movement is present.
These signs can include doors or windows binding, uneven floors, gaps between walls and ceilings, separation around window frames, internal cracking corresponding with external cracking or cracks that continue to increase in width.
A crack that has previously been filled and has subsequently reopened can also indicate that movement has continued after the cosmetic repair was completed.
Multiple symptoms throughout a property can provide a much clearer picture than one isolated crack.
What About Cracking Above Windows and Doors?
Stepped or diagonal cracking is commonly found around windows and doors.
Foundation movement is one possible cause, but it is not the only explanation.
The steel lintel supporting the masonry above an opening should also be considered. Corrosion, deterioration or movement of the lintel can contribute to cracking around the opening.
This is another reason why diagnosing brick cracking from a photograph alone can be difficult.
The surrounding construction needs to be inspected.
Should I Repair Stepped Cracks Straight Away?
Simply filling stepped cracks with mortar may improve their appearance, but it does not necessarily address the underlying cause.
Before undertaking significant repairs, it is preferable to determine why the cracking occurred.
If drainage problems, soil movement or another building defect remain unresolved, repaired cracks may reopen.
In some circumstances, monitoring the cracking over time may assist in determining whether movement is continuing.
Where significant structural movement is suspected, further specialist investigation may also be recommended.
Stepped Cracking When Buying a House
Stepped cracking deserves particular attention during a pre-purchase building inspection.
A prospective purchaser may see a repaired crack and assume that the problem has been fixed.
However, cosmetic repairs do not necessarily mean the underlying cause has been rectified.
Fresh mortar, render or paint may sometimes conceal evidence of previous movement.
During a building inspection, we look for visible cracking together with other indicators such as movement around doors and windows, uneven flooring, external drainage problems, ground conditions and corresponding internal cracking.
This helps provide a more complete understanding of what may be occurring.
Professional Building Inspections in Melbourne
If you have discovered stepped cracking in your home, or you are considering purchasing a property where cracking is visible, it is worthwhile having the property professionally inspected.
We carry out building and pest inspections throughout Melbourne and assess visible cracking together with other building and site conditions that may help identify the likely cause of movement.
Stepped cracking does not automatically mean that a house has a serious structural problem. However, it should not simply be filled and forgotten without considering why it occurred.
The important questions are:
What caused the movement? Is the movement continuing? And does further investigation or repair appear necessary?
