Unlike the UK, traditional underpinning is rarely used in Ireland to address subsidence problems. It is more often applied where a foundation needs extending downwards for basement construction or where other works are being completed close to shallow foundations. Our most common underpinning type works are completed where inadequate projections do not allow for borehole formation in grouting projects. Then, a pad is formed either beneath or beside the footing, depending on the specification.
This project was completed for a local building contractor, Carrigbell Construction, during extensive renovation works to a residential property in Douglas. An old rear extension with a random rubble foundation needed to be extended downwards both to mitigate the risk of further movement and to accommodate a new insulated concrete floor.
The key difference in this project when compared to normal underpinning works was that a 300 mm projection on the new underpin would not accommodate the new insulated concrete floor and services, both internally and externally. To overcome this, rising walls were installed between the new underpin and formation level. The final pinning up was completed by dry-packing with a semi-dry non-shrink grout rammed into place from both sides.