How to make a deed for sharing rooms/floors of a house.

Sir, We have a 2 storied house on a plot measuring 1.5 katha constructed by my father. The ground floor is occupied by my brother while I stay in the first floor which is tin roofed. Recently, I have extended the house and constructed 2 new floors adjoining to the existing building taking homeloan which is paid by me only. Again I give the ground floor of this new part to my brother and take the first floor but without any agreement. I also expressed my brother that since I had spent a huge amount for the new floors, the space above the floors will be in my control and I can only build house there in future and my brother have no control over this area which is also agreed by my father too. Now, my question is since we did not make any agreement, will there be any problem in future. I want to make an agreement for the property. Please advice how to go about it.