First of all, it depends on whether the occupied terrace is owned by the owner. If it is owned by the owner, it is illegal whether the house is built or not. If the terrace is privately owned by the owner, it depends on whether there is a clause prohibiting the construction of "sun room" in the relevant treaty. If there are relevant provisions, then the owner can't build it; If the balcony is privately owned by the owner and there is no relevant regulation prohibiting the construction, then if the owner wants to build a "sun room", he should also report it to the property, communicate with the property and developers, and go to the relevant departments for approval without affecting the lighting and use of others.
Illegal construction refers to houses and facilities built outside the planning area without obtaining the planning permit of the proposed project (original site and site selection) and in violation of the provisions of the Land Management Law, the Urban and Rural Planning Law, the Regulations on Planning and Construction of Villages and Market Towns and other relevant laws and regulations. Illegal buildings have the characteristics of occupying safe passage, illegally occupying cultivated land, affecting urban public space and destroying ecological environment. Many illegal buildings are still hidden in legal buildings. Illegal buildings damage the credibility of the government, destroy the urban landscape, restrict the healthy development of the city and the implementation of urban and rural planning, and also affect the future development of the city. According to national regulations, illegal buildings should not only be demolished, but also the parties involved in illegal buildings should bear all the expenses incurred in dismantling illegal buildings.