I carried out waterproofing repairs on my concrete roof before the last
monsoons. I had faced some leakages so I decided to call in a contractor to get
the job done. He used a flexible waterproof coating that not only worked well
that monsoon but is still going strong! I was very impressed with his work so I
asked him what he used. He used a waterproofing compound called roff hyguard. I
could see first-hand how effective it was so it definitely could be something
that you could try.