Flat Roof Waterproofing at Residence House by admin | Feb 5, 2015 | Uncategorized | 0 comments Problems: Water Seepage and Leakage from the Flat Roof Top to the Car Porch and Living Hall Area Area : 1500 SF Solutions : Koster 21 Project Photo: 1. Jet Wash and patching the cracks area 2. First Coat of Koster 21 3. First Coat of Koster 21