Active or historic movement
Crack monitoring to tell if movement is active or historic
One inspection shows a crack as it is today. Crack monitoring shows whether it's still moving. We install tell-tale gauges or measured points across selected cracks, take a baseline reading and re-read them on a set schedule, so you know whether movement is stable, seasonal or progressive before anyone designs a repair.
- Tell-tales or measured points
- Scheduled readings
- Stable, seasonal or progressive
Overview
What is crack monitoring?
The short answer
Crack monitoring is the repeated measurement of selected cracks against a first, baseline reading. Tell-tale gauges or measured points are fixed across each crack and read at set intervals, and the readings show whether the movement is stable, seasonal or progressive. In other words, whether it's historic or still active.
A single inspection can measure how wide a crack is today, but not whether it's growing. On reactive clay, cracks often open and close with the seasons, so one reading taken in a dry spell or a wet one can mislead. Repeat readings against a baseline show the trend underneath.
- Tools
- Tell-tale gauges or measured points
- Compared with
- The first, baseline reading
- Readings
- At set intervals, agreed in your quote
- What it shows
- Stable, seasonal or progressive movement
- Alert thresholds
- Can be agreed where a project needs them
- Fee
- Fixed quote per job, before we start
Key takeaways
- The first reading is the baseline every later reading is compared with.
- One visit can't show a trend. A series of readings can.
- Seasonal and progressive movement need different responses.
- We design and certify repairs if they're needed, but never sell them.
Method
How does crack monitoring work?
Gauges or measured points are fixed across each selected crack, a baseline reading is taken, and the cracks are re-read on a schedule agreed in your quote. Every reading is compared with the baseline.
Tell-tale gauges
A gauge fixed across the crack, one half on each side, so opening, closing or sliding shows against its grid.
Measured points
Fixed points either side of a crack, measured the same way at every visit so the readings stay comparable.
A baseline reading
The first reading, taken when the gauges or points are installed. Every later reading is measured against it.
Scheduled readings
Readings at set intervals, over a period long enough to show the pattern on your site.
A running log
Each reading logged against its baseline, so any change is visible at a glance.
An engineer's interpretation
What the pattern means and what to do next, from a structural engineer who doesn't sell repairs.
| Point | Location | Method | Visit | Baseline | Latest | Trend |
|---|---|---|---|---|---|---|
| T-01 | Front wall, bed 1 | Tell-tale | 4 | 0.0 mm | +0.1 mm | Stable |
| T-02 | Hallway, door head | Tell-tale | 4 | 0.0 mm | +0.4 mm | Seasonal? |
| M-01 | Rear corner, outside | Measured points | 4 | 3.2 mm | 4.1 mm | Widening |
| M-02 | Garage side wall | Measured points | 4 | 1.0 mm | 1.0 mm | Stable |
Illustrative example only. Tell-tales read movement from zero at installation; measured points record the crack width. "Seasonal?" marks a crack that needs readings across the seasons before it can be called.
Timeline
What does a crack monitoring timeline look like?
From choosing the cracks to the final recommendation. The schedule and period are agreed in your quote.
- Before monitoring
Inspect and select the cracks
Usually after a foundation and crack report, the engineer chooses the cracks that will show how the house is moving.
- First visit
Install and take the baseline
Tell-tales or measured points fixed across each crack, and the first readings recorded.
- Each scheduled visit
Read and compare
Every gauge read and logged against its baseline, on the agreed schedule.
- If agreed thresholds are passed
Flag significant change
Where alert thresholds have been agreed, a reading past them is flagged and reported to you.
- End of the period
Report and recommend
The pattern, what it means and the next step: no action, maintenance, further testing or a repair to be designed.
What sets the schedule and the fee?
- How many cracks need gauges or measured points
- How many readings are needed, and over what period
- The site: on reactive clay, readings often need to span the seasons
- Alert thresholds, where the project needs them
Send the address and photos of the cracks. You'll get a fixed quote within 1–2 business hours, before anything is installed.
Reading the results
Stable, seasonal or progressive: what do the readings mean?
Plotted over time, readings fall into three broad patterns, and each one points to a different next step.
- Stable means historic movement. Readings stay at the baseline. The crack formed in the past and isn't moving now, so filling and repainting may be all it needs.
- Seasonal means active but cyclical. The crack opens and closes as soil moisture changes, which is typical of reactive clay. Managing moisture around the footings, such as leaks, drainage and trees, may be part of the answer.
- Progressive means active and getting worse. The crack keeps widening. The cause needs confirming, sometimes with further testing, and a repair may need to be designed.
Why timing matters
A crack read at the end of a dry summer and again in a wet winter can look as if it has closed, when it's only following the seasons. Readings spread across the seasons show the trend underneath, and that's what a repair decision should rest on.
Illustrative example: stable, seasonal and progressive crack readings
- Stable
- Seasonal
- Progressive
View the data
| Months since the baseline reading | Stable | Seasonal | Progressive |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 1 | 0.02 | 0.23 | 0.23 |
| 2 | 0 | 0.39 | 0.43 |
| 3 | 0.03 | 0.45 | 0.59 |
| 4 | 0.02 | 0.39 | 0.69 |
| 5 | 0 | 0.23 | 0.75 |
| 6 | 0.02 | 0 | 0.78 |
| 7 | 0.03 | -0.23 | 0.81 |
| 8 | 0 | -0.39 | 0.87 |
| 9 | 0.02 | -0.45 | 0.97 |
| 10 | 0.03 | -0.39 | 1.13 |
| 11 | 0 | -0.23 | 1.33 |
| 12 | 0.02 | 0 | 1.56 |
Monitor or repair now?
When is monitoring better than an immediate repair?
When the crack isn't a safety concern and no one yet knows whether it's still moving. Repairing a crack that's still active can mean doing the work twice, and a repair designed without knowing how the house is moving may not suit it.
Monitor first when
- The crack isn't a safety concern and its cause isn't yet clear
- A leak, downpipe or drainage problem has just been fixed, and you want to see if the movement settles
- The cracks may be seasonal, opening and closing with the weather
- A repair design needs to know how much the house is still moving
- You've bought a house with old cracks and want to know if they're historic
Don't wait on monitoring when
- Walls lean or bulge, or door and window frames distort
- There are any signs of instability
- A leak is still soaking the ground: fix the leak now, then monitor
- Cracks are widening quickly or new ones keep appearing
- The engineer advises that work is needed now
Can you monitor a crack yourself?
Yes, and it's worth doing. A dated pencil mark at each end, a measurement at the widest point and a photo from the same spot every few weeks give an engineer useful history. Our guide to cracks in walls shows how.
Engineer-led monitoring adds fixed gauges or measured points, a consistent method, a log against a baseline and an interpretation you can act on. That matters when the readings will inform a repair design, or a report for an insurer or a dispute.
Where monitoring fits
Monitoring usually follows a foundation and crack report or a house structural inspection, when the engineer needs to know whether movement is still active. If a repair is needed, we provide underpinning design and certification, and any licensed contractor can build it.
Related services
Other reports we prepare
House structural inspections
A structural engineer inspects the whole house, finds what's moving and why, and reports what, if anything, needs doing.
Learn more Cracks · Subsidence · MovementFoundation & crack reports
Cracks measured and rated, the cause of the movement found, and your options set out before anyone quotes a repair.
Learn more Homeowners · Builders · ContractorsUnderpinning design & certification
If underpinning is needed, we design it, prepare the permit documents, inspect the critical stages and certify the work.
Learn moreQuestions
Crack monitoring FAQs
Still unsure? Call 07 2150 0579 and an engineer will talk it through.