Things to look for when buying a block of land - Geotechnical classifications.A geotechnical engineer will usually drill two to three boreholes on the land in the area where the slab or foundations will be located. These bore samples are then sent to a lab for analysis and a report will be written which will include a classification reference using the following Class system:A CLASS - Sand/rock with little or no ground movement.S CLASS - Slightly reactive clay.M CLASS - Moderately reactive clay.H1 CLASS - Highly reactive clay.H2 CLASS - Highly reactive clay.E CLASS - Extremely reactive clay.P CLASS - Problem site with uncontrolled fill, trees, collapsing soils and/or land-slip.A structural engineer considers the information contained in the geotechnical report (including the soil classification) and then designs the most appropriate slab/foundations/footings for the dwelling to be built on.It is important to note that even though boreholes have been drilled and soil samples were taken, unforeseen circumstances, such as hitting rock or finding asbestos buried in the block, may become apparent once work starts on site and digging commences.We provide expert advice on things to consider when buying a block of land. For more information, go to