The study has critically focused on the grassroots who are not supported by public housing can only rely on the private rental market. They are faced with the situation of living in more expensive and smaller spacing, and even forced to move into subdivided housing to suffer from different challenges in various aspects. Unfortunately, the number of grassroots living in subdivided housing will increase in the future, and the problems of subdivided housing will become more serious. The researcher selected five young adults who are living in subdivided housing for in-depth interview. Their housing expenditure is about 33%, reflecting the high burden of housing expenditures on the grassroots. The study identified that residents living in subdivided housing face different challenges in various aspects. Endanger personal safety, fire hazard, leaking water, concrete peeling, hygiene issues, and mental health are all unsatisfactory. They often lack relevant safety awareness and support. They are often exposed to risks, especially in old buildings and suburban squatters. The research result indicated that living in subdivided housing for long periods of time may be detrimental to the physical, mental, social development, and health of residents. The small living environment of children also hinders their learning, growth, and development. Therefore, different strategies should be adopted to overcome the challenges and difficulties faced by residents living in subdivided housing. Suggestions are provided for the government to improve the safety and health issues of subdivided housing in Hong Kong.