The contractor or the builder may or may not engage the services of professionals to design and construct the house or the apartment that you wish to buy.
In the absence of control over the design of the structure as per Indian Standards requirement for RCC design, the durability, the quality and safety of the structure suffers.
This leads to loss of life and property.
Therefore it is necessary to ensure that the house/apartment/villa that one proposes to buy meets the quality requirements.