First, the expansion gaps reserved between floor tiles and between floor tiles and surrounding walls are too narrow! When the room temperature changes dramatically, floors, cement layers and tiles will expand with heat and contract with cold. For example, if the gap is too thin and there is not enough space for the tiles to "stretch", the tiles are prone to arching, which is easy to appear in the north, and the humidity in the south is high and the temperature difference is small, which is not easy to appear.
Second, when laying floor tiles, cement and yellow sand were not mixed in the correct proportion. If the cement grade is low, put yellow sand, the lower cement will not stick to the floor tile for a long time, causing the floor tile to tilt.