Is it against the property law to dig the floor heating ground wire 15 cm slot for upstairs decoration?

At present, there is no legislation on property management in China. The highest law concerning the property management industry and owners is the Property Law of People's Republic of China (PRC), and the highest law is the Property Management Regulations of the State Council. There is no so-called "property law".

According to your description, the 15cm floor heating trough should be excavated on the ground and used for the decoration of upstairs units, which should be plane length rather than vertical length, because the thickness of the floor slab pouring layer between floors will not exceed 20cm. If it is vertical, such trunking has damaged the floor casting layer.

As for whether the decoration has caused damage to the building and affected the stability and safety of the building structure, only the building appraisal department with professional qualifications can draw a conclusion with legal effect, while the inference and appraisal of other institutions, departments or individuals have no legal effect.