Need legal help.

Q: Hi All,
In my property, for odd number floors flats have straight dry balcony is attached to kitchen door (Entry door to dry balcony from kitchen) and for even number floor flats have "L" shaped dry balcony. I am leaving on 5th floor so there is vacant space on top side in my dry balcony from upper flat (i.e. 6th floor).
Issue is the upper flat owner has put the slab on that vacant space which blocks the light and air to come in my flat.
This portion should remain vacant as per building plan which I have received from builder. Also the project is new and still do not form society and run by builder.

Please advise me for necessary action.

Thanks and Regards,
Vikram