Rain can definitely affect the structural integrity of a building if it is not properly waterproofed! When water penetrates the surface of a building, it can cause mold growth, rot, and deterioration of building materials such as wood, concrete, and steel. Over time, this can weaken the structure and lead to significant damage and even collapse. Therefore, it is important to ensure that a building is properly waterproofed for the safety of those that occupy the said building.