Redevelopment of old apartment building

Dear Sir, Our building is 34 years old. There are 15 flats. We do have a owner's association & bank account in the name of association for all the common expenses. We do have a managing committee with properly elected representative. But our association is not a registered housing society. All 15 occupants do have a registered sale deed. Now, apart from 3 ground floor owners all other flat owners want to go in for redevelopment of the building. Can we go for it. If yes then,What's the process? How many owner's signatures are required to pass the resolution in AGM of Association?