Builder is not paying compensation 4 delaying project for 2 yrs

I want to file a case against the builder for non paying compensation/interest for delaying project for 2 years. Below please find the builder response to my compensation request. Total cost of the flat: 29 lakhs 69 Thousand Paid till 29th June, 2014: 26 lakhs 72 thousand Interest component builder should pay due to delay: 4 lakhs 50 thousand till today Property Location: Devanahalli, Bangalore As per builder buyer agreement, flat was to be delivered on or before 30th June, 2014 with all amenities. Flat has not been delivered till date. Builder buyer agreement was signed on 5th December, 2012. As per builder buyer agreement page no 10, point no 20, the vendor/developer agrees to construct and handover the flat with all amenities on or before 30th June, 2014. Builder Response to my email request: Builder is denying to pay any compensation/interest with below cause. Please refer to the clause no.19 on page 10 of our Sale Agreement dated 5/12/2012 wherein the point of non availability of materials/other factors are mentioned. We acknowledge that the project has be delayed and inspire of our sincere efforts to finish the project on time we have been hit badly by some factors which was beyond our control and to an extent may be you can call it act of god. When we say act of god,during the escavation for the basement and for the fottings we had to encounter hard rock which had to be drilled,broken up and extracted out and that was a cumbersome process where we lost about 4 months as we could not blast the rocks due to objection from the local people.