What to do when owner refuses to address leakage from flat above?

RESPECTED SIR, I HAD PURCHASED A SMALL FLAT BEFORE 6 YEARS. i.e. I AM STAYING ON 1ST FLOOR FLAT IN AHMEDABAD FOR LAST 6 YEARS. 2ND FLOOR FLAT (JUST ABOVE MY FLAT) IS OWNED BY NRI (INDIAN ORIGIN BUT SETTLED IN CANADA). THERE IS A TERRACE ON HIS FLAT. IN SHORT OURS IS A LOW RISE FLAT (GROUND + 1ST FLOOR FLAT & 2ND FLOOR FLAT). BEFORE 6 YEARS, WHEN I PURCHASED 1ST FLOOR FLAT, IT WAS ABSOLUTELY FINE & NO LEAKAGE PROBLEM. BUT BEFORE TWO YEARS, NRI (2ND FLOOR OWNER) WHO IS STAYING JUST ABOVE MY FLAT, RENOVATED HIS FLAT & CHANGED TILES IN WHOLE FLAT & LEAKAGE PROBLEM IS STARTED. WE CALL HIM & SHOWED THE LEAKAGE PROBLEM & ALSO REQUESTED HIM RESOLVE SUCH LEAKAGE PROBLEM BUT HE IS NOT GIVING ANY ATTENTION TO SUCH PROBLEM. HE USED LAST WORDS THAT HE WILL NOT TAKE ANY ACTION TO STOP SUCH LEAKAGE & DO WHAT EVER YOU LIKE. SIR, MAY I KNOW THE REMEDIES UNDER THE LAW WHICH I CAN INITIATE AGAINST SUCH NRI.