Construction of new basement externally within reinforced waterproof concrete walls and reinforced concrete slab. The internal basement was constructed by extending the existing foundations using an underpinning method and the these walls were then lined with a 150mm concrete wall. The ground was battered back and the excavation done in a piecemeal way. We installed the drainage and sump pumps installed for waterproofing. Waterproof concrete was used as the first line of defence and the internal walls were finished with a delta membrane.