Praise be to Allah.
This is not permissible, because it is not permissible to interfere with graves in any way so long as any remains of the dead are still to be found in them. The sanctity of the dead is like the sanctity of the living. So it is not permissible to subject graves to any disrespect, whether by stepping on them, making them pathways, praying in the graveyard, or making them part of people’s dwelling-places. None of these things are allowed, unless the occupants of the graves have turned to dust and there is nothing left of their bodies. In that case, it is OK to use the graveyards for fields or houses or other purposes. But so long as any trace of the dead bodies are left, it is not permissible to use them or walk on them, because the dead Muslim came to this place before you; he got there first so he has more right to it. His sanctity when he is dead is the same as his sanctity when he was alive. When the Prophet (peace and blessings of Allah be upon him) saw a man step on a grave, he said: “If one of you were to sit on a live coal that burned his garment and reached his skin, that would be better for him than sitting on a grave.” (Narrated by Muslim, 9711; Abu Dawood, 3228). This is a warning, because of the disrespect towards that Muslim that is involved. The scholars stated that it is haraam to relieve oneself in between graves, and that it is not permitted to sit on a grave, because the Prophet (peace and blessings of Allah be upon him) said: “Do not sit on graves, and do not pray towards them.” (Narrated by Muslim, no. 972; Abu Dawood, no. 3229). We should not lean on graves, or step on them, or show any disrespect towards them; all of that is not allowed. And Allah is the Source of strength.