Cellars & Basements

Do you know your basement from your cellar?

 

It’s all down to the designed purpose. Typically, cellars are designed as storage spaces, whereas basements are often finished off as living spaces. Either way, both can prove a problem on development site, particularly if they are now known about prior to starting site works.

 

Ideally the location of any basements and cellars would be investigated at design stage before any development work takes place, but it is as important before siting a crane or erecting scaffolding.

 

The most suitable geophysical technique is Ground penetrating Radar (GPR). This is a high-resolution technique which offers depth information and allows the data to be analysed in plan or section view.

 

The contrast between the roof of a basement or cellar and the space beneath produces a large electrical contrast which is detected by the GPR.  In general, if the construction is simple and flat, the reflections from the roof of the basement should be reasonably smooth and planar (flat) responses. Vaulted basements tend to produce steeply curved upper reflections. The amplitude of the reflected signal diminishes significantly if a basement has been backfilled. If a cellar is full of stock or is disused and has collapsed internally the reflections characteristics become more complex.

 

The GPR data below was collected prior to scaffolding being erected around a building. Three possible basements/cellars were identified at c. 0.7m depth. The planar responses suggest that these are of flat roof construction.