Delay in the delivery of the house

Location/place: Chennai

Name of company/service: Kasthuri Constructions FIRRM

Dear sir,
The builder agreed to complete the construction of our house on or before 30th September 2012, and in case of any delay of handing over,the builder agreed to pay a rent of Rs.3000/-per month.But neither he is completing nor he is paying the rent.I have the original agreement paper,all payment details with the receipts.Kindly help me.