What is the sharia ruling on an uncle demanding the construction of a third floor for him in a house that the father built entirely, knowing that the father was the one who built the ground floor for the uncle, and that the father, his three sisters, and his grandmother are more entitled to the inheritance than the uncle?

The determination of who has the right to build the third floor and above depends on what the uncle owns of the house. If his share is only the ground floor, then he does not have the right to build the third floor, and the right belongs to the father because he owns the second floor.

However, if the uncle has an undivided share of the house and it is not designated to the ground floor, then the right to build the third floor and above is shared between the father and the uncle. Neither of them has the right to build independently except by mutual agreement. For whoever owns the land owns the air above it.