How To Monitor A Crack Opening

Read our guide on how you can easily and accurately monitor a crack using demec studs or tell tale gauges.

Article By: Tom Ayre | Last Update: April 2022

In this article, we are going to discuss how you can easily monitor a crack within your home. The methods described are relatively low cost and will give you an indication if a crack is opening or closing.

Knowing if a crack is getting bigger and how long it is taking can be an indicator of further problems within your property. Knowing if a problem is getting worse can be help to trigger further action to get the issue rectified.

If you wanted to read more about cracks, their causes etc then please visit this article from

Let’s have a look at how you can monitor cracks.

Table of Contents

Tell Tale Gauges

tell tale crack gauge
Cost Per Crack
£10 to £20
Additional ToolsNone
Other ItemsAdhesive / Wall Plugs / Screws
Typical Accuracy0.25 to 0.5 mm
Dimensions MonitoredUp, Down, Left,Right
Ease Of InstallationEasy

A tell-tale crack gauge uses 2 plates laid over each other with a marked out measurement grid on one side and a precise cross-hair mark on the other.

Each plate is secured either side of the crack, over time, if the crack moves the plates will move over each other. The cross-hair which starts at 0 mm will indicate the direction and magnitude of movement.

Tell-tale gauges are very useful because they can illustrate movement and can show if the crack is getting bigger or smaller in a certain direction.

Tell-tale gauges can be purchased from a number of different websites. At THS Concepts, we use SCCS.


  • Can be used to check direction of movement (up, down, left, right).
  • No additional tools required, such as a measuring calipers.
  • Easy to read.


  • Relatively high costs to monitor multiple cracks.
  • Installation can be a little cumbersome.
  • Not suitable for cracks where the other side of the crack isn’t flush.

How To Install Tell Tale Gauge

  • Determine the crack and location you want to monitor. Is it suitable for a tell-tale gauge?
  • Using a permanent marker, write a reference number on the tell-tale gauge and the installation date.
  • If using adhesive, glue each side of the gauge either side of the crack and wait for it to dry.
  • If you are using wall plugs and screws then secure, use the gauge screw holes as reference, mark the wall and then install.
  • Once the adhesive has cured or the gauge is secure using screws, the plastic screws holding the 2 plates together can be removed.
  • If you don’t remove the plastic screws, then the 2 plates will stay together, so no movement will show.
  • You are now ready to start monitoring, using your phone, take a picture of the newly installed gauge. This will be useful for the future!
tell-tale monitor with glue
Tell-tale crack gauge secured to wall with glue.
tell-tale corner gauge
Tell-tale corner gauge secured with glue.

How To Monitor A Crack - Tell Tale Gauges

Monitoring a tell-tale gauge is very simple. Simply take a photograph, square on to the gauge and observe the movement in the X (along) and Y (up / down) axis.  Record these figures down along with the date. This will then be used for further analysis into the future! Having a photograph on your phone is a useful backup in case you lose the data.

Demec Studs

Demec studs secured to wall
Cost Per Crack
Additional ToolsMeasurement Calipers
Other ItemsAdhesive
Typical Accuracy0.1 mm (check calipers)
Dimensions Monitored1 direction
Ease Of InstallationModerate

Demec studs are extremely simple in their nature, they have a small dimple in the middle of the disk that a measuring caliper can measure to. When used in a pair, the measuring caliper can record the distance between the 2 disks. The measurements can then be compared over time to see if the crack is opening or closing.

Measuring calipers vastly range in price dependent on the brand and quality. We would recommend getting a digital set which show the display electronically. You can purchase a decent measuring caliper for £50, we have seen some as low as £10, but we question the quality!

Demec studs are installed either side of a crack and secured using high strength adhesive. A high quality measuring caliper is recommended to ensure you reliably and accurately record the distance between the 2 disks.


  • Very easy to install, just a dab of glue on each disk.
  • Very small and low cost per crack, a bag of 100 costs around £50.
  • Not as obtrusive as a tell-tale gauge.


  • You need a measuring caliper tool to measure the distance between each disk.
  • You can only monitor in one direction.
  • Not suitable for cracks in corners or close to other objects (pipes, boiler etc).

How To Install Demec Studs

  • Determine the crack and location you want to monitor. Is it suitable for a demec stud?
  • Using a dab of glue, stick each disk either side of the crack you want to monitor.
  • Using a permanent marker, write a reference number on the wall and the installation date.
  • Once the adhesive has set, you can now record the distance between the disks using the measuring gauge.
  • Measure the distance a few times and average out the results to ensure optimal accuracy.
  • Record the distance, crack reference number and the installation date and keep this somewhere safe!
Monitoring a wall with demec studs.
Measuring demec studs with a measuring caliper.
Demec studs monitoring horizontally and vertically
Demec studs monitoring horizontally and vertically

How To Monitor A Crack - Demec Studs

Monitoring a demec stud is quite a simple process, but does require an accurate measuring caliper. Before you begin, you must make sure your calipers are correctly zeroed. This can be easily checked by closing your calipers and checking the display shows 0. Most calipers allow you to reset to 0 if this number doesn’t show 0.

Once your calipers are set, then you can measure the dimples on each stud. We would recommend taking a few measurements, zeroing your calipers, and then average out the readings. Once you have the reading, write down the date, reference number and measurement. Store this data somewhere safe, so you can easily access it in the future!

Looking For Help?

• Site visits to install crack monitoring.
• Post setup and ongoing reports & graphs.
• Fixed-price quotations.

Edward Sadler - Davis Construction
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