Whether or not house plans need to be engineered will depend on the specific design and the requirements of local building codes and regulations. In general, more complex or unusual house designs may require engineering to ensure that the structure is safe and meets all necessary building codes.
An engineer can provide calculations and drawings to ensure that the house will be structurally sound and able to withstand the forces that it will be subjected to, such as wind, snow, and seismic activity. They can also help to ensure that the house is built to comply with local building codes and regulations, including requirements for fire safety, energy efficiency, and accessibility.
In some cases, engineering may be required by local building authorities as a condition of obtaining a building permit. If you are planning to build a house, it's a good idea to consult with a licensed architect or builder to determine whether engineering will be needed for your specific project. They can help you evaluate whether engineering is required, and if so, provide guidance on how to obtain the necessary engineering services.