Human activity monitoring is a fascinating area of research to support autonomous living in the aged and disabled community. Cameras, sensors, wearables, and non-contact microwave sensing have all been suggested in the past as methods for identifying distinct human activities. Microwave sensing is an approach that has lately attracted much interest since it has the potential to address privacy problems caused by cameras and discomfort caused by wearables, especially in the healthcare domain. A fundamental drawback of the current microwave sensing methods is non-line-of-sight environments. They need precise and regulated conditions to detect activity with high precision. In this paper, we suggest the intelligent reflecting surface (IRS) to assure high accuracy activity monitoring in complicated environments where traditional microwave sensing is ineffective. This work is based on reconfigurable IRS that can perform beam-forming/beam-steering and intelligent machine learning algorithms that can accurately recognise several human activities. For experimentation, the transmitter and receiver are positioned on two separate floors of a building. A complicated multi-floor scenario is created in order to test the IRS. Multiple activities such as sitting, standing, and walking are performed on the floor of the building by two individuals, a male and a female. It has been proven through an experiment that IRS technology increases detection accuracy by around 30% compared to conventional microwave sensing without IRS technology.