in pagdi system do teenant have right to build the house again?

Dear sir , We are teenant (pagdi system)from more than 50 years in delhi. After my grandfather died the rent slip was transferred to my father without any problem. The house is divided in two parts , we live in upside & downside one more teenant is living .. Now the problem is that the house is very old around 100 years &it is in bad condition now .. I have discussed this problem with the teenant who is living downside he is also agreed . We are worried that the house is not strong .there are cracks which are increading day by day . we have tried to make the house strong and spend lot of money to make house strong. Can we rebuild the house again in this case where the house is in very bad condition.?? If the society or land lord didnt agreed to rebuild the house then what step we should take?? Can we write letter to landlord describing him the problem & who will be responsible if house falls ?? Can we give our area to builder for flats ?? If the landlord or society concerns will get agree then what documents we should take from him ?? Kindly please guide us the right way ..