Which department should I report to for illegal decoration?

You should complain to the property about illegal decoration. If you don't care about the property, you should call the Housing Authority. House decoration violations mainly include unauthorized decoration without the approval of the property company; Unauthorized changes to building structures, pipelines, pipelines and other facilities and equipment; Changing the use function of the house without authorization; Indiscriminate use of naked flames, smoking, etc. When decorating residential houses, as owners, we can't change the structure and appearance of houses without authorization, and we can't change the functions of houses and supporting facilities. Only the floor, indoor wall and roof of the house can be changed, but it can't be chiseled on the original floor to avoid damaging its waterproof layer.

property management regulations

Article 45

The realty service enterprise shall stop the violation of laws and regulations such as public security, environmental protection, property decoration and use in the realty management area, and report to the relevant administrative departments in a timely manner.

After receiving the report from the realty service enterprise, the relevant administrative department shall stop the illegal act or deal with it according to law.