Is it permissible to construct a building over the entire area of a petrol station that contains a mosque, by changing the location of the mosque and sufficing with a prayer room (musalla) within the new building, or by appraising the current mosque and building another in a different location with its value?

It is not permissible to demolish or relocate a mosque unless there is a benefit to the endowment, such as if the mosque is abandoned or becomes too small for the worshippers. This is because a mosque ceases to be the property of its builder and becomes an endowment for Allah once the call to prayer is made therein for people. It is not sufficient to designate a prayer room for workers in a room or similar, as prayer rooms in offices or girls' schools do not take the ruling of a mosque.