Riddlesdown Apartments is a eight-unit residential development on a steeply sloping site in Purley, Surrey. The project required substantial excavation and basement construction to unlock the site and establish a workable platform for the new building, adding significant structural and technical complexity from the outset. Above the basement structure, the development was constructed using Structural Insulated Panels (SIPs), allowing much of the superstructure to be assembled rapidly while improving thermal performance and reducing construction time. The completed scheme provides a mix of one, two and three-bedroom apartments, combining efficient planning with a construction strategy that reduced carbon emissions by approximately 20% and significantly shortened the programme. The project demonstrates our experience of combining complex groundworks, alternative methods of construction and coordinated residential delivery on constrained sites.