Last edited 05 Nov 2020



The term ‘ground’ typically refers to the solid surface of the Earth or an area that is used for a specified purpose.

It can also be used to refer to the storey of a building that is on the ground, i.e. ‘ground level’ or ‘ground floor’.

In terms of the physical matter of the ground, it is made up of different layers. Topsoil is the first, upper layer of soil, typically measuring between 5 - 20 cm (2 - 8 inches) deep. It can also be measured as the depth from the surface level to the subsoil, i.e. the distance to the first densely-packed layer of soil. Subsoil is the layer (or stratum) of soil immediately underneath the surface topsoil. Beneath the subsoil is the substratum - a layer of residual bedrock, sediments or deposits.

The ‘water table’ is the below-ground level that marks the transition between ground that is saturated with water and ground that is not saturated. The upper, unsaturated level, is known as the 'capillary fringe' or 'zone of aeration'.

In terms of construction, ‘groundworks’ refers to work done to prepare sub-surfaces for the start of construction work. Aside from any demolition or site enabling works that may need to be carried out, groundworks are usually the first stage of a construction project.

Ground investigations are a means of determining the condition of the ground, ideally before beginning construction works. They focus specifically on intrusive geotechnical work such as trial pits and boreholes. An assessment of ground conditions typically includes geology, hydrology, hydrogeology and soil conditions of a site and surrounding, along with any contaminated land.

There are a number of ground improvement or ground modification techniques that can be used to stabilise or improve the condition of an area of ground before construction work takes place. This may be necessary to improve or modify the ground shear strength, stiffness, permeability, and so on.

Designing Buildings Wiki has a number of articles relating to the ground, including:

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