(Note: In Tractate Sanhedrin 48a, the discussion refers to a grave that was dug and a “nefesh” that was built at the site. Rashi explains that “nefesh” in this context refers to a structure such as an ohel – a mausoleum above the reserved plot. Obviously, we do not place a body above ground in a mausoleum; rather, in lieu of a monument, a structure, an ohel, a mausoleum, is built over the deceased’s burial plot.)
The Rambam clearly states that the whole site is restricted from use unless there is a clear demarcation between the row of stones that was added and the original structure. In such a case, the site may be used when the added stones are removed. If, however, the person for whom it was intended was buried there and subsequently removed, the site remains permanently forbidden for future use.
The Tur (Yoreh De’ah 364:4) rules that even sitting on a grave, on the stones that cover a grave, or on the soil of the grave is not permitted since all these are considered to be items that were uprooted and subsequently re-attached, and thus they have become part and parcel of the grave itself. He quotes his father, the Rosh, who maintains that one may sit on the stone since it is not part of the grave but rather a grave marker on it (see Bayit Chadash and Perisha, ad loc., who refer to it as just a sign). The Tur then quotes the Gemara (loc. cit.) as a basis for forbidding the use of the structure above a grave site in perpetuity only if it was built specifically for the deceased who was buried there but later removed elsewhere.
Nowadays, monuments are placed on graves after burial, and, thus, they might not be considered part of what was specifically prepared or built for the deceased prior to his death.
(To be continued)