What is Islamically permissible and impermissible concerning a cement grave built above ground, where the grave is opened to bury a new deceased by placing the bones of the previous deceased in a corner of the grave?

It is not permissible to construct graves in the form of rooms where the bones of a previous deceased person are thrown to bury a new deceased person in their place. This is due to the sanctity of the deceased, and "breaking the bone of a deceased person is like breaking it when they are alive." Furthermore, the grave is a confinement for the deceased, and it is not permissible to exhume it as long as its occupant is within it. It is also forbidden to introduce a new deceased person to a grave with another before the complete decay of the first. This contradicts the Sunnah (definition) of graves.

However, this ruling applies in cases of choice. As for situations of necessity, such as a shortage of land or a high number of deaths, it is permissible to combine multiple deceased persons in one grave out of necessity.