My concrete flat roof is 2 years old. Above the roof I have fixed terracotta tiles. During heavy rains I find water leakages (dropping) inside my house in several places. Water drain is perfect. No water stagnation after rain stops. I couldn't find any cracks, holes in my roof. Kindly suggest me how to find out the exact leakage point. I would be ever thankful for your valuable suggestion. I want to get rid of this problem.