Seeing cracks in a relatively new house can be worrying, but not every crack means the building is structurally failing.
Buildings move. Concrete shrinks. Timber moves with changes in moisture. Foundations respond to changes in the ground beneath them.
The important question is whether the cracking and movement are within the expected tolerances for the building, or whether they indicate a defect or an underlying structural problem.
Queensland Has a Standards and Tolerances Guide
The Queensland Building and Construction Commission (QBCC) publishes a Standards and Tolerances Guide for homeowners, builders and contractors.
The guide provides a practical reference for a wide range of building issues, including cracking, movement, finishes, floors, walls, doors, windows and other aspects of residential construction.
You can find the current guide on the QBCC Standards and Tolerances Guide page.
The Guide Is a Starting Point, Not the Whole Engineering Assessment
Crack width alone does not tell you everything about the condition of a building.
When assessing movement or cracking, it can also be important to consider:
- where the cracks occur;
- the direction and pattern of cracking;
- whether the cracks are changing;
- whether doors and windows are sticking or distorting;
- whether floors have changed level;
- the age and construction of the building;
- the footing and slab system;
- soil and moisture conditions;
- site drainage;
- plumbing leaks;
- nearby vegetation; and
- the history of the damage.
The QBCC guide itself recognises different categories of damage and that the history of the movement needs to be considered.
Some Cracking Is Expected
Minor cracking can occur in otherwise satisfactory buildings.
For example, plasterboard joints, masonry, concrete slabs and finishes can develop small cracks as materials dry, shrink and respond to normal building movement.
That does not mean every crack should simply be dismissed as normal settlement.
The pattern, severity and progression of cracking matter.
Watch for Changes, Not Just a Single Measurement
If you are concerned about cracking, photographs are extremely useful.
Take clear photographs and record the date. If appropriate, include a ruler or another scale in the photograph.
Over time, this can help establish whether the crack is:
- stable;
- opening;
- closing seasonally;
- continuing to develop; or
- appearing alongside other signs of movement.
Good records can be very useful if the builder, QBCC or an engineer later needs to assess what has happened.
Look Beyond the Crack
A crack is often the visible symptom rather than the underlying problem.
Where movement is occurring, possible contributing factors can include:
- uneven soil moisture;
- poor site drainage;
- leaking plumbing;
- downpipes discharging near the building;
- changes to landscaping;
- trees close to foundations;
- inadequate footing performance;
- construction defects; or
- a combination of several factors.
Repairing the crack without understanding the cause may simply result in the crack returning.
Raise Concerns With the Builder Early
If your home is relatively new and you are concerned about cracking or another construction defect, notify the builder promptly and keep the communication in writing.
Provide photographs, identify the location of the problem and describe whether it appears to be changing.
There can be time limits associated with building complaints and insurance schemes, so significant concerns should not simply be ignored indefinitely.
When QBCC May Become Involved
Where a dispute concerns potentially defective residential building work, QBCC may assess the work against relevant requirements including the National Construction Code, applicable Australian Standards, manufacturer’s requirements and the Standards and Tolerances Guide.
The process and applicable time limits depend on the circumstances, so homeowners should refer to the current information published by QBCC rather than relying on an old copy of a guide or advice found online.
When Should a Structural Engineer Inspect?
An independent structural engineering assessment may be worthwhile where:
- cracking is continuing to develop;
- there are several related cracks;
- doors or windows are noticeably sticking or distorting;
- floors appear to have moved;
- there are concerns about slab or footing movement;
- the builder and homeowner disagree about the significance of the damage;
- previous repairs have failed;
- drainage or plumbing problems may be contributing; or
- you need an independent technical opinion.
The engineer’s job should be to investigate what is happening and why, rather than simply measure the width of a crack.
Do Not Panic, But Do Not Ignore Significant Changes
Minor cracking can be part of normal building behaviour.
At the same time, increasing cracking, noticeable distortion or continuing building movement deserves proper investigation.
The QBCC Standards and Tolerances Guide is a useful starting point, but the condition of the whole building and the cause of the movement are often more important than any single crack measurement.
Need an Independent Assessment?
Cornell Engineers investigates selected cases involving cracking, building movement, foundation performance and disputed structural defects.
Send us the property address, photographs, relevant builder correspondence and any previous reports. We can review the information and advise whether a structural engineering inspection is likely to assist.