50 years old Dweling House

We own a 50 years Old house G + 1 (Madras Terrous I.e. Roof without Steel rods), My grand Father made a Registered Will to my Father and my small Father, stating that the Ground Floor belongs to small Father and First Floor belongs to my Father. Due to the Building was too old, we can't able to stay in First Floor, it is getting Leakage and Wiring problems etc. Now, we like to construct a House there how we need to claim our property. ? In Apartment Act How it is Described ? Anyone suggest a Good IDEA pls