Mr. Feng Shui, what's happening on the roof at night?
1. There are animals like cats making noise in the room.
2. There is a gap between building cement materials, and there is a temperature difference during the day and night, which makes a sound when it expands with heat and contracts with cold.
Extended data
Thermal expansion and cold contraction of cement materials
In the final analysis, the function of watering is actually to replenish water. Hydration is a chemical reaction, which makes various components of concrete react and closely combine together to meet the strength requirements. Theoretically, the wetter the place, the longer the time, the higher the strength of concrete. Another function is to dissipate heat. When concrete is hydrated, its internal high temperature can reach above 60 degrees. Ordinary thermometers can explode instantly, and water can take away the heat emitted from the concrete surface through evaporation. Excessive hydration heat will lead to cracks in concrete. Thereby making a sound.
References:
Baidu Encyclopedia/Cement expands with heat and contracts with cold (copied from others)