Cracks in internal walls and ceilings are extremely common in homes throughout Melbourne.
Some are minor cosmetic defects caused by normal movement, shrinkage or ageing of building materials. Others may be warning signs of foundation movement, moisture problems, movement within the roof structure or other building defects.
One of the questions we are regularly asked during building inspections is:
“Should I be worried about these cracks?”
The answer depends on much more than simply measuring the width of the crack.
An experienced building inspector considers the location, direction, pattern and extent of the cracking, together with other signs of movement throughout the property.
Why Do Internal Walls Crack?
A house is constantly subjected to small amounts of movement.
Building materials expand and contract as temperature and moisture conditions change. Timber framing can move, plasterboard joints can develop minor separation and foundations may experience some movement over time.
Minor hairline cracks therefore do not automatically indicate a serious structural problem.
However, cracking becomes more important when it is substantial, appears suddenly, continues to increase or is accompanied by other signs of building movement.
1. Hairline Cracks in Plaster Walls
Fine hairline cracks are commonly found in plaster and plasterboard walls.
They may develop along plasterboard joints, around cornices or where different building materials meet.
In many cases, these cracks are cosmetic and can be repaired during normal maintenance.
However, repeatedly repairing a crack that continues to reopen may simply be hiding the symptom rather than identifying the underlying cause.
If the same crack continues to return, further investigation may be worthwhile.
2. Diagonal Cracks Around Windows and Doors
Diagonal cracking extending from the corners of windows and doors deserves closer attention.
Openings create areas within walls where stresses can become concentrated.
If movement occurs within the foundations or building structure, cracking may develop diagonally from these locations.
A diagonal crack does not automatically mean that major structural movement has occurred, but it becomes more significant when combined with other symptoms such as binding doors, windows that no longer operate correctly, external brick cracking or uneven floors.
3. Cracks Where Walls Meet Ceilings
Cracking or separation where internal walls meet ceilings is another defect frequently identified during building inspections.
Minor separation may occur because different building materials move at different rates.
However, significant separation can sometimes indicate movement within the roof framing, ceiling structure or walls.
The inspector should therefore consider whether the cracking is isolated or whether similar movement is occurring elsewhere.
Where cornices have separated from walls or ceilings, the condition of the surrounding ceiling and roof space may also need to be considered where accessible.
4. Cracks Across Ceilings
Cracks running across ceilings may occur along plasterboard sheet joints.
Poor installation, inadequate fixing, movement of framing members or deterioration over time can contribute to this type of cracking.
Other signs may include nail or screw popping, sagging plasterboard, separation between plaster sheets or cornices pulling away from the ceiling.
A minor joint crack may simply require maintenance.
However, noticeable ceiling sagging, widespread cracking or evidence that ceiling sheets are becoming inadequately supported should not be ignored.
5. Foundation Movement Can Cause Internal Cracking
One of the more significant causes of internal wall cracking is movement of the building’s foundations or footings.
Many areas of Melbourne contain reactive clay soils that can expand and contract as their moisture content changes.
During extended dry conditions, clay soils may shrink. Following substantial rainfall, they may expand again.
Where these changes occur unevenly beneath a building, sections of the foundations can move differently.
This movement can be transferred through the walls and become visible as internal cracking.
6. Poor Drainage May Be Part of the Problem
When investigating internal cracking, it is important to inspect outside the house as well.
Blocked gutters, leaking downpipes, poor surface drainage, garden beds located against external walls and paving that directs water towards the building can alter soil moisture conditions around the foundations.
The crack may be inside the bedroom or living room, while a contributing drainage problem may actually be outside the building.
This is why simply inspecting and repairing the visible crack may not identify the actual cause.
7. Internal and External Cracks in the Same Area
One of the important things we look for during a building inspection is whether internal cracking corresponds with external cracking.
For example, there may be a diagonal crack above an internal window opening and stepped cracking through the external brickwork in approximately the same location.
When internal and external signs correspond, they can provide useful evidence about the pattern of movement occurring through that section of the building.
This does not automatically mean major structural repairs are necessary, but it is an important observation that should not be overlooked.
8. Doors That Bind or Floors That Are Uneven
Cracking should never be assessed completely in isolation.
Other visible signs can help determine whether movement may be occurring.
These may include:
- Doors that bind against their frames
- Windows becoming difficult to open or close
- Uneven gaps around doors
- Sloping or noticeably uneven floors
- Separation between skirting boards and flooring
- Gaps between walls and ceilings
- Stepped cracking to external brickwork
- Cracking around multiple windows and doors
- Cracks that continue to reopen after repairs
A single small crack may have little significance.
Several related symptoms throughout the property may require a much closer assessment.
9. Could Moisture Cause Wall or Ceiling Cracking?
Not all internal cracking originates from foundation movement.
Roof leaks, plumbing leaks, failed waterproofing and prolonged moisture exposure can affect plasterboard, timber framing and other building materials.
Moisture-damaged plasterboard may deteriorate, sag or crack.
Timber framing can also expand when exposed to moisture and shrink as it dries.
Where cracking is accompanied by staining, mould, swelling, deterioration or elevated moisture readings, the possibility of water ingress should be investigated.
Should I Repair the Cracks Straight Away?
Cosmetic repairs should not necessarily be the first response to unexplained or substantial cracking.
Filling and repainting a crack may make the wall look better, but it does not establish why the crack occurred.
If the underlying movement continues, the crack may simply reopen.
Where appropriate, monitoring cracking over a period of time may help determine whether movement is stable or continuing.
Significant or progressive movement may require further investigation before permanent repairs are undertaken.
Internal Cracks When Buying a House
Cracking is particularly important during a pre-purchase building inspection.
Buyers should be cautious where sections of walls or ceilings appear to have been recently patched or painted.
Fresh paint does not necessarily mean there is a problem, but recent cosmetic repairs can sometimes make the history of cracking more difficult to assess.
During a pre-purchase inspection, we look beyond the individual crack.
We assess visible internal cracking together with external brickwork, doors, windows, flooring, ceilings, drainage, ground conditions and other accessible areas of the property.
The objective is to establish whether the cracking appears to be an isolated cosmetic issue or part of a broader pattern of building movement.
When Should You Be Concerned About Internal Cracks?
Cracks should receive closer attention where they are substantial, increasing in size, repeatedly reopening or accompanied by other signs of movement.
Cracking that suddenly appears in several areas of a property should also be investigated.
The significance of cracking cannot reliably be determined from a photograph or crack width alone.
The condition of the surrounding building needs to be considered.
Professional Building Inspections in Melbourne
If you have noticed cracks developing in your internal walls or ceilings, or you are considering purchasing a property where cracking is visible, a professional building inspection can help identify other visible evidence that may explain what is occurring.
We carry out building and pest inspections throughout Melbourne, using extensive visual inspection together with appropriate inspection equipment to assess accessible areas of the property.
Not every crack in a wall or ceiling means that a house has a serious structural problem. However, cracks should not automatically be dismissed as cosmetic without considering why they developed.
The important questions are:
What caused the cracking? Is movement continuing? Are there other signs of movement? And does the underlying cause require further investigation or repair?
