Inexpensive methods of undertaking a crack survey in buildings

Common causes of cracking in buildings can include:

Landslip on sloping ground
Foundation subsidence
The expansion and shrinkage of clay soils with changes in moisture content
Leaking water services and slope drainage
Made or filled ground

Crack widths can be measured by use of a proprietary crack width gauge. The characteristics of each crack [width, direction, taper & frequency] can be plotted onto a sketch of the building.

Proprietary gauges, using the generic name "Tell-Tales" are an inexpensive, easy to install method of crack monitoring. 'Tell-Tales' manufactured to ISO 9002 are accurate to a resolution of 1.0mm and by interpolation to 0.5mm. They can record horizontal opening and closing of the crack as well as vertical shear movements. They are ideal for plotting the trends and direction of movement and verifying the adequacy of remedial work.

Precision calipers are used for more accurate monitoring. The distance between two datum points fixed either side of the crack is measured with the jaws of the caliper.. The datum points are 6mm stainless steel discs with a hole drilled in the centre into which the jaws of the caliper are placed.

Reference: Roger W. Johnson CEng. FIStructE. FICE. MRICS, Technical Director of Avongard Ltd, UK ' The significance of cracks in low-rise buildings'.

For more information see: www.avongard.co.uk