Basement impact assessment (BIA) for new basement

The clients had requested a basement impact assessment (BIA) for a new basement to be constructed beneath the existing property. The basement has been built under the entire footprint of the existing dwelling.

The purpose of this BIA was to assess site geology, site hydrology, CPG4 screening flow charts, construction methodology, outline temp and permanent works, ground movement and damage assessment.

The basement was constructed using sequential underpinning methodology, a series of foundation blocks serving as an extension of the existing foundation.

This method involves excavating beneath the existing foundation in small sections approximately 1m wide.  Steel reinforcement was then fixed into position as per the structural engineers design.  Once the steel was fixed, and using formwork, concrete was poured to form the new, extended foundation.  This process was repeated until a new, continuous foundation is constructed fully supporting the existing foundation above.

Photo Credit:  JMS Engineers