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How To Monitor A Crack Opening

Crack Monitoring Made Easy: A Step-by-Step Guide Using Demec Studs and 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.

Keeping tabs on a crack’s size and rate of growth can help you spot potential issues with your property. By identifying problems early, you can take swift action to rectify the situation and prevent it from worsening.

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.

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Table of Contents

The Importance In Monitoring Cracks In Buildings

  • Cracks in buildings can be a sign of structural problems or other issues, and it is important to monitor them closely in order to identify and address any underlying issues as soon as possible. Some common reasons why cracks may appear in buildings include:

    1. Foundation problems: Cracks in walls or floors can be caused by problems with the building’s foundation, such as settlement or heave. These cracks may be wider at the top or bottom, and may be accompanied by other signs of foundation problems, such as doors or windows that are difficult to open or close.

    2. Moisture damage: Cracks in walls or floors can also be caused by moisture infiltration, which can weaken the structural integrity of the building. This type of damage may be accompanied by other signs of moisture damage, such as peeling paint or wallpaper, or a musty smell.

    3. Aging or wear and tear: Over time, buildings can experience wear and tear that can lead to cracks and other types of damage. This may be due to natural aging, or it may be caused by other factors, such as changes in temperature or humidity.

    By regularly monitoring cracks in buildings, it is possible to identify and address any underlying issues before they become more serious and costly to repair. It is especially important to pay attention to cracks that are growing or spreading, as these may be a sign of a more serious problem. If you notice cracks in your building, it is a good idea to consult with a professional, such as an engineer or contractor, to determine the cause and appropriate course of action.

Crack Monitoring Equipment / Tools

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!

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