How crack monitors are used to check for movement.
The worst thing that can happen to a home, and to its owner, is cracks appearing in its walls.
The first question is whether the crack that has appeared is significant or serious. But if more cracks also appear around the home, concern reaches its peak.
If owners find that multiple stepped cracks are appearing in their home, and they can also hear the house “creaking”, they should consult a professional without further delay, so that an in-depth analysis can be made of what is happening to their home.
To measure how a crack is developing and whether it is active, plaster tell-tales (patches of plaster placed over the crack) have traditionally been used to determine whether the crack was still active. If the plaster broke, it meant that the foundations were still moving and had not stabilised.
Today technology has moved on, and plaster has been replaced by crack monitors (the most common and simple ones are those in the image above; there are also glass ones). Crack monitors are fixed over the crack, covering or bridging the two “split” sides of the wall, and over several months they are checked to see whether “the walls have opened further”. If the lines no longer match, the amount by which the crack has opened can be measured to the millimetre, and this means that the process is still active and there is no guarantee it will stop. In our image, the crack monitor measured a movement of 0.5 millimetres over a period of 2 months.
At the same time, the architect must analyse the geotechnical survey and the project to determine the origin of the problem, which may have various causes: the characteristics of the ground, inadequate foundations, washing out of the soil beneath the foundations by groundwater or by a burst water supply pipe, etc.
All kinds of tests, study of documentation and analysis of data must be carried out to determine not only the origin of the cracks but also the most effective and permanent way of repairing them; and, if there is legal liability and the building is still under guarantee, a court claim will be brought for the repair of the structural and foundation defects affecting the home.
Any questions?