All perfect praise be to Allah, The Lord of The Worlds; and may His blessings and peace be upon our Prophet Mohammad and upon all his family and companions.
Muslim scholars have agreed that it is forbidden to exhume graves because violating the sanctity of the dead isn`t permissible, as reflected by the Hadith where the Prophet(PBUH) said, “Breaking a deceased body’s bones is exactly like breaking them when he is alive.”{Abu Dawoud}. And since Allah, The Almighty, said, "Verily we have honoured the Children of Adam."{Al-Isra`, 70}, part of this honor lies in not exhuming graves nor violating the sanctity of the dead.
In fact, burying the dead in "Fusqiahs" doesn`t comply with the rules of Sharia and thus it isn`t permissible. Resolution No.(126) of the Jordanian Iftaa` Board forbids burying more than one dead person in a grave, and it stated the following: "In principle, it is imperative that each deceased person is buried in one grave, and it isn`t permissible to bury more than one person in a grave if that wasn`t necessary.
However, in case of necessity: When there are many deceased persons and it is difficult to bury each in a separate grave, burying them in one grave is permissible. If the deceased person was buried in a grave, it isn`t permissible to build any structure over it, except that which preserves their corpse and keeps it in its place. Moreover, it isn`t permissible to bury a deceased person over another as indicated by the Hadith of Jabir(May Allah be pleased with him), who said, "The Messenger of Allah (PBUH) forbade that the graves should be plastered (made into permanent structures), used as sitting places (for the people) or building over them."{Muslim}.
In addition, the grave should be in an underground hole, because the Prophet(PBUH) said about those killed in the Battle of Uhud, " 'Dig graves and make them good and deep………"{Sunan An-Nassa`i}.
In conclusion, it is impermissible to build graves over each other because they, in fact, become like the big drawers of hospitals` mortuary fridges, and not graves in the sense that preserves the sanctity of the deceased. Moreover, there is no need for burying more than one person in one grave since the desert is very vast, a human being is only buried once, and wherever there is a cemetery people can reach it. And Allah knows best." One can`t fail but to notice that in our country the bones of the dead don`t decompose save after a hundred years, and it isn`t permissible to add layers of dirt on old graves to new ones over it until making sure that the bones have completely decomposed. It is also conditioned that the burial process should comply with the rules of Sharia. And Allah knows best.