Is it permissible, in Islamic law, to open a grave and move the deceased for the purpose of rebuilding the cemetery, given that the deceased was buried there five months ago?

The fundamental principle is that it is impermissible to construct graves, rather, they must be leveled to about a handspan above the ground. Building upon graves is not allowed except out of necessity, such as fearing that the deceased might be exhumed or dug up. If there is no need for construction, it is not permissible to exhume or move the father's grave; it must be left as it is. However, if there is a necessity that permits construction, then it is permissible to move it for that purpose, because exhuming a grave and moving the deceased from it is not allowed except for a legitimate reason.