Why Is My Commercial Premises Sinking?

If you have recently built a commercial property that has started to sink, or you have purchased commercial premises that have signs of subsidence, there are several potential causes of this. However, the most common and pressing are those that begin in the soil. 

• Expansive Soil 

Expansive soils are those which are heavy in clay or silt. These soils are heavily reactive to moisture and will change their volume based on the amount of water they hold. If your property sits on clay-based soil that is heavily saturated as a result of heavy rainfall or poor drainage, subsidence is a potential outcome. 

When expansive soils are dehydrated – for example, as a result of drought – they can shrink dramatically. This shrinking can lead to gaps between your foundation and the soil below; this is only compounded by the fact that these soils can also crack as they sink. These voids leave your foundation unsupported, and as a result, it can settle into them, causing cracks and unevenness in the floor above. 

• Loose Backfill Soil 

During construction, a large swathe of the ground is excavated to allow for the construction of your property and its foundation. Once the structure is complete, any remaining spaces will be filled with the excavated soil. Known as backfill, this soil is far looser than the virgin soil around and under it. As a result, it is weaker to things like frost, rain, and dehydration. 

Loose backfill soil can cause damage to your foundation in several ways, but the most common is the creation of a ‘clay bowl’. This term refers to what happens when loose backfill becomes saturated; the virgin soil around it prevents water from draining as quickly as it accumulates. This puts pressure on a property and can cause sinking, spreading cracks, and bowing walls.