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Structural Monitoring / FILE 12

Crack Movement Monitoring

Not all cracks are getting worse. Crack monitoring measures whether cracking is stable, seasonal, or progressive. This data drives better remediation decisions and avoids unnecessary repair.

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Crack Movement Monitoring on a real Australian project siteEVIDENCE / CRACK-MOVEME

Crack movement monitoring measures changes in crack width over time to determine whether cracking is stable, cyclical (seasonal thermal movement), or progressive (ongoing structural distress). This distinction is critical for deciding whether repair is needed, when it is needed, and what type of repair is appropriate.

We install precision displacement sensors (LVDTs) and tell-tale gauges across cracks at selected locations. LVDTs provide continuous digital measurement with resolution to 0.001mm, transmitted wirelessly to cloud platforms. Tell-tales provide a simple visual record of cumulative movement at lower cost.

A minimum of 12 months of data is required to capture one full seasonal thermal cycle. Concrete and masonry structures expand and contract with temperature, causing cracks to open and close cyclically. Without 12 months of data, cyclical movement can be mistaken for progressive cracking, leading to unnecessary remediation.

Monitoring results are presented as time-series plots showing crack width against temperature, enabling clear identification of the movement pattern. Where monitoring confirms progressive cracking, the rate of deterioration informs the urgency and type of intervention required.

Capabilities

What we deliver

8 deliverables across the crack monitoring engagement.

  • 01LVDT displacement sensors (0.001mm resolution)
  • 02Mechanical tell-tale gauges for visual monitoring
  • 03Wireless data transmission to cloud platform
  • 04Temperature-correlated crack movement analysis
  • 05Seasonal thermal cycle identification
  • 06Progressive cracking rate determination
  • 07Multi-point monitoring across building elements
  • 08Automated alert for threshold exceedance

Process

Our methodology

01

Crack Assessment & Sensor Placement

Visual assessment of all cracking, selection of monitoring locations at representative and critical cracks, and installation of LVDT sensors or tell-tale gauges.

02

Baseline & Commissioning

Initial crack width measurement, sensor commissioning, cloud platform configuration, and alert threshold setting based on BRE Digest 251 damage categories.

03

Data Collection (12+ months)

Continuous crack width and temperature data collection over at least one full seasonal cycle. Periodic interim data review and status reporting.

04

Analysis & Final Report

Time-series analysis with temperature correlation, determination of stable/cyclical/progressive behaviour, and recommendations for repair or continued monitoring.

Use cases

Common applications

  • Residential cracking investigation
  • Strata building crack assessment
  • Retaining wall movement tracking
  • Heritage building structural monitoring
  • Post-repair crack observation
  • Insurance claim evidence
  • Adjacent construction crack tracking
  • Subsidence and settlement monitoring

Frequently asked questions

4 questions answered.

Q01

Why is 12 months of monitoring needed?

Buildings expand and contract with seasonal temperature changes. Concrete, masonry, and steel all have thermal expansion coefficients that cause cracks to open in winter and close in summer (or vice versa depending on element orientation). Without 12 months of data, it is impossible to distinguish this normal cyclical movement from progressive structural cracking. A crack that widens by 0.5mm over 6 months may simply be responding to cooling. Only a full annual cycle reveals the true behaviour pattern.

Q02

What is the difference between a tell-tale and an LVDT?

A tell-tale is a two-part plastic gauge bonded across a crack. Movement is read visually against graduated scales. An LVDT (linear variable displacement transducer) is an electronic sensor that measures displacement with 0.001mm resolution and transmits data digitally. Tell-tales are cheaper and suitable for monthly manual readings. LVDTs provide continuous automated data ideal for temperature correlation analysis. We often use both: LVDTs at critical cracks and tell-tales at secondary locations.

Q03

How wide does a crack need to be before it is structural?

The BRE Digest 251 classification system is widely used. Category 0 (less than 0.1mm) is negligible. Category 1 (up to 1mm) is fine cracks requiring no action. Category 2 (up to 5mm) requires filling and may indicate structural movement. Categories 3 to 5 (5mm to 25mm and above) indicate significant structural damage requiring engineering assessment. In reinforced concrete, cracks wider than 0.3mm may affect durability by allowing moisture and chloride ingress to reinforcement.

Q04

Can monitoring prevent the need for repair?

Yes. If monitoring demonstrates that cracking is stable or cyclical (thermal), no structural repair may be needed. Cosmetic filling for aesthetics may be sufficient. This is particularly relevant in strata buildings where repair costs are significant. Monitoring data provides the evidence to justify a less expensive maintenance response versus a full structural remediation programme. This often saves owners tens or hundreds of thousands of dollars.

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