Evaluation of Foundation Types Used in Multi-Storey Buildings in Kano Metropolis

Foundation selection in multi-storey residential and commercial buildings in Kano metropolis is frequently made without adequate geotechnical investigation, contributing to differential settlement and structural distress. This study evaluates the types of foundations used in multi-storey buildings in Kano metropolis and assesses their adequacy relative to underlying soil conditions. Geotechnical data were compiled from site investigation reports submitted to Kano State Physical Planning Authority for 45 building projects from 2018 to 2023, supplemented by interviews with 30 structural engineers and site supervisors. Foundation types, depths, bearing pressures, and design soil parameters were tabulated and assessed against soil profile data. Results indicate that pad foundations on dense sand are used in 48 percent of projects, raft foundations in 31 percent, pile foundations in 14 percent, and strip foundations in 7 percent. Pad foundations on shallow sandy layers show the highest incidence of reported settlement problems, occurring in 28 percent of pad foundation projects. Settlement problems are least frequent in piled foundations. The standard penetration test is the most commonly employed in-situ test, used in 58 percent of investigations. The study concludes that foundation design in Kano metropolis would benefit from a minimum investigation standard specifying borehole depths and test frequencies for different building heights, recommended for adoption by the Kano State Building Code.

Keywords: foundation types, geotechnical investigation, multi-storey buildings, Kano metropolis, settlement