Settlement Cracks

Inspection Requirements

• Map all visible cracks across internal and external surfaces, recording width, length, orientation and location relative to structural elements.
• Measure crack widths using a calibrated crack width gauge — classify as hairline (<0.1 mm), fine (0.1–0.3 mm), medium (0.3–1 mm) or wide (>1 mm).
• Assess whether cracks are active (still moving) or dormant using tell-tale gauges or plaster witness marks installed at crack locations.
• Inspect the pattern of cracking — diagonal cracks at window corners and stepped cracking in brickwork are characteristic of differential settlement.
• Review geotechnical and structural drawings to understand founding conditions and load paths relative to crack locations.
• Inspect the building perimeter for evidence of ground movement — heave, subsidence, differential movement at slab edges or garden beds.
• Check for associated door and window binding, distorted frames or gaps at junctions that may indicate ongoing structural movement.
• Engage a structural engineer to assess crack severity and determine whether further geotechnical investigation or monitoring is required.

Typical Repair Methodology

Settlement crack repairs must be preceded by structural assessment and a monitoring period. Repairing active cracks without addressing the root cause will result in recurring failure.

1. 01.Engage a structural engineer to assess all cracks and confirm the diagnosis of settlement — rule out thermal movement, shrinkage or loading-induced cracking before proceeding.
2. 02.Install crack monitoring gauges (tell-tales) at active cracks and record readings over a minimum 4–8 week period to quantify movement rate and direction.
3. 03.Address any ground-related causes contributing to settlement — improve site drainage, remove tree roots, repair leaking services or address fill compaction issues.
4. 04.Where differential settlement is ongoing and significant, engage a geotechnical engineer to assess underpinning or ground improvement options.
5. 05.For dormant cracks in masonry, prepare crack faces by raking out loose material, dust and contamination to a minimum depth of 20 mm.
6. 06.Fill dormant fine to medium cracks in masonry with a flexible, breathable pointing mortar compatible with the substrate.
7. 07.Inject dormant medium to wide cracks in concrete elements with low-viscosity epoxy resin under controlled pressure to restore structural continuity.
8. 08.For active cracks, install a flexible backer rod and apply a paintable polyurethane or polysulfide sealant that accommodates ongoing movement.
9. 09.Reinstate all affected plaster, render and decorative finishes following crack repair using compatible materials.
10. 10.Apply a crack-bridging paint system over repaired areas to maintain a uniform finish and reduce risk of surface crack re-appearance.
11. 11.Re-inspect and re-measure monitoring gauges at regular intervals post-repair to confirm movement has ceased.
12. 12.Record all repair works with photographs, product details and monitoring data for warranty and strata records.