rented property

Dear Sir we have a old (before 1970) rented property in Delhi (taken on rent by my grandfather who is passed away two year back) it has been overheard that actual owner had sold that property around 1990 to third party who never approached us for rent or any thing else. though few builders tried to threaten my grandfather to evacuate the premises. There after my grand father file a case against the actual owner that he is not approaching us for rent, after a long procedure, the court has given us a ex-party degree as no one had present in front of court stating that no one can evacuate us force fully from the said premises. now the problem is that the structure get old and need reconstruction to be reside but being there is no owner where to approach for getting approval for repair/reconstruction. I got to know that MCD will give the permission so i visit MCD office several time but due to lack of information i failed to contact the correct authority/Dept. I will be grateful if some one advice me further.