Tell Tale Crack Monitor

Cracks often appear in a building. They may be just hairline cracks and of little significance or they may the first sign of a serious defect.

The crack may not increase in width and therefore would be static. However it may progressively increase in width over time. This progressive movement may suggest there is a serious defect in the foundations and / or the superstructure.

Monitoring and recording progressive changes in the width of the crack over time will confirm or otherwise the nature of the defect and assist with diagnosing the cause.

Sometimes cracks will open and then partially close, and then open again before partially closing again following a cyclic pattern of movement. Again monitoring and recording the changes of width over time and perhaps correlating the crack movements with external factors will assist with identifying the cause.

How To Monitor A Crack
Monitoring in isolation to any other investigation will rarely provide sufficient information to fully diagnose the cause of cracks. But it will indicate how the building is deforming and the rate at which movement is occurring. The results of the monitoring are a vital ingredient for diagnosing the cause.

Because crack monitoring takes time, it is essential it starts at the earliest opportunity and continues throughout the period of inspections and investigations. In some instances it can be continued to validate the remedial work.

A simple device called Avongard Tell Tale can be placed over the crack. This would provide precision monitoring the progressive width and indicate the direction of movement both horizontal and vertical movement.

The Avongard Tell Tale features two plates which overlap, the bottom plate contains a calibrated grid in millimeters with the top transparent plate containing precision cross hair which slides over the grid and shows any movement.

A detailed positive or negative reading can be read from the position of the cross hair on the graduation of the underlying grid to an accuracy of +/- 1.0mm and by interpolation to +/-0.5mm.

Avongard provide a crack recording sheet with every instrument to allow the surveyor to accurately record the position of the cross hairs on the opposing grid, building a pattern of movement over a period of time.

Application example
A useful application of using Tell Tales for crack monitoring would be illustrated by the following scenario:

An existing building is to be demolished to make way for a new development. There are existing buildings either side. Before demolition starts, the owner or the advisers of the building to be demolished inspects with the owners of the adjoining buildings any cracks in their buildings.

The widths of the cracks are measured using an Avongard Crack Width Gauge as part of the present condition survey and Tell Tales are fixed across any cracks.

The position and reading of each Tell Tale are agreed with all interested parties. All interested parties countersign the crack monitoring sheet. At agreed stages during the demolition, foundation and superstructure construction, all interested parties again read the Tell Tales for signs of movement and countersign the crack monitoring sheet. This procedure can reduce the incidence of disputes and claims with adjoining owners.


If you have a requirement for measuring a crack in a building or structure or even a concrete floor, visit our range of Avongard crack monitoring tell tales