Gianni Botsford Architects

This house in a garden required a 2.5 storey basement to create living spaces and a swimming pool at the lowest level–see separate project sheet for pavilion.

the garden boundary walls were repaired and underpinned prior to installation of a contiguous piled retaining wall forming the new basement perimeter wall

internal sacrificial piles were also installed to aid the excavation sequence

the basement excavation progressed in a top down sequence with the RC slabs being cast onto the ground and connected to the perimeter piles and internal sacrificial piles

sections of tread riser and balustrade sub-assemblies were made off site prior to site assembly

the tread-riser sections, and the balustrade, incorporate flexible carpentry detailing to accommodate the anticipated seasonal movement

the solid Douglas fir stair cantilevers from internally threaded dowels resin fixed flush to the marble clad RC stair wall

the stair is fixed to these via long loose hex drive bolts which are housed within a resin fixed sleeve set within the stair riser

the 6mm folded profile treads and 8mm plate balustrade were made off site in manageable sub-assemblies that could be connected together on site

intense scrutiny was given to the visible bolted joints between the stringer and balustrade sections to achieve visual coordination with the wall connection detail