If it is built by the unit, it is not illegal. The bungalows we used to live in all had extended kitchens, but the kitchen and bungalows were integrated, not built separately. It should be illegal for every household to build another kitchen at the door. If it doesn't affect the traffic, and it is within the dormitory of the factory, the general urban management will not take care of it. If you encounter demolition, the square house you built will be worthless. Demolition is mainly based on household registration and resettlement houses.