The property is flat.

From the description and picture information you provided, we can analyze it from the following aspects:

1. Floor heating installation and ground treatment

You mentioned shoveling the ground flat and laying it warm. Under normal circumstances, the installation of floor heating really needs to treat the ground to ensure the flatness and heat dissipation effect of the heat dissipation pipeline. However, if the construction process is carried out in strict accordance with the specifications and the main structure of the floor is not damaged, the installation of floor heating itself is unlikely to cause bulging or cracking of the ceiling downstairs.

2. The reason for the bulge in the ceiling downstairs

There may be many reasons for bulging, such as poor material ratio, improper construction and excessive indoor humidity. Judging from the pictures you provided, the cracks are all white ash, which probably means that the cracks existed before scraping. Therefore, the bulging and cracking of the ceiling downstairs may be related to the original construction quality, material problems or environmental factors, rather than the floor heating installation upstairs.

3. Property management and judgment

Property personnel handled the bulging and took photos, but could not determine the specific reasons. This may be because the causes of bulges and cracks are complicated and require detailed inspection and analysis by professional construction or decoration personnel.

4. Overlord Agreement and Responsibility Ownership

The overlord agreement signed downstairs is not legally binding, and the responsibility attribution needs to be judged according to the actual situation and evidence. If the downstairs insists that the bulge and cracks are caused by the floor heating installed upstairs, sufficient evidence needs to be provided to support this statement.

In view of this situation, we suggest that you take the following measures:

Communicate with the downstairs in a friendly way, explain the installation process of floor heating and the possible impact, and invite them to check and analyze with professional building or decoration personnel.

If both parties cannot reach an agreement, they can contact the property or relevant departments for mediation or arbitration.

If necessary, you can seek legal channels to resolve disputes. Before this, it is recommended to collect relevant evidence, such as construction contracts, photos and videos. To prove his innocence and safeguard his rights and interests.

In short, when dealing with such problems, we need to remain calm and rational and solve them in a reasonable way.