Cracks in a new Mambourin slab: tolerance or defect?
How slab cracks are measured against the Guide to Standards and Tolerances 2015.
In short: Slab cracks between 2mm and 4mm have been recorded at Mambourin handovers. Here is how they are assessed.
Width is the starting point
The Guide to Standards and Tolerances 2015 sets crack widths for slabs. Cracks over 2mm and up to 4mm are treated as moderate and defective in the reports we write.
Pattern matters too
Where the crack runs and whether it is moving point to the cause, whether shrinkage, settlement or soil movement.
Reactive ground
Mambourin's basalt derived clays move with moisture. Investigations look at drainage and grading as well as the slab.
What the report gives you
Measured widths, photos, the tolerance and the next step, such as monitoring or engineer review.
When it becomes a dispute
If the builder disagrees, the BPC dispute resolution service and VCAT need an expert witness report.
Written by our local inspection team from work carried out in Mambourin. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.


