The Residential sector:

Subsidence Ground Stabilisation


Underpinning of Shaftesbury Avenue Overview:


• Initial site survey, council dug trial pits to identify tree roots
• Excavation of materials prior to the underpinning process
• Traditional dry pack with stainless steel dowel underpinning method
• Return the site to the client’s agreed condition as outlined in the project brief


Traditional Underpinning of

Shaftesbury Avenue for Folkestone & Hythe District Council:


Folkestone & Hythe District Council housing officers had been alerted by their tenant to significant cracks in the property, on Shaftesbury Avenue in Folkestone. Upon inspection of the cracks, it was noted that the property was close to some mature trees and further investigation would be necessary, to establish if the trees were the cause of the issues. The council carried out the excavation trial pits in three areas. The trial pits confirmed that tree roots were present and drawing water from the clay soil, causing clay shrinkage, a common cause of subsidence.

Restek identified the areas requiring underpinning and provided a marked up drawing identifying the locations of any drainage/utilities locations around the property. During the underpinning process, drains were visually and remotely monitored ensuring that no excess material migrated into the drains causing a blockage. Restek’s underpinning schedule included excavating trenches to set depths, and underpinning pits to a depth of 1.65m. The pits/trenches for the new pad foundations were filled in sequence as specified by the council and allowed to cure, for the required time. The sides of the foundations used letterbox shuttering and concrete shear keys were inserted. Restek took test cubes from each delivery of concrete to ensure that the materials were to the correct specification. Once the material spec was confirmed, Restek poured each underpinning pit one at a time.

How long does it take to complete the ground stabilisation process?


Residential ground stabilisation work can often be completed in one to two days and, due to its non-invasive nature, there is usually no need to move out the property before or during the work being carried out. This is entirely dependent on each individual project. Any disturbance of areas around the property during the underpinning process is returned to its original state after any works have been completed, which leaves little to no trace of the work that has been carried out beneath the ground.