Constructing A Wall Around A Qabr (Grave)

A  grave is not a place of eternity and conservation; rather, it is a place of destruction and decomposition. Therefore, it is against the spirit of Shariah to put up the writings on the graves, and for this reason it is prohibited in a few Ahadith. However, to put up an inscription board or place a stone on the side of a grave for identification purposes is allowed. 

In the enquired case, constructing a small wall will not be allowed as it is understood from the Ahadith that prohibit hardening the graves, building upon it, etc..

Nabi Sallallahu Alayhi Wa Sallam forbade that the graves should be plastered (made into permanent structures), used as sitting places (for the people) or building over them.

It is for this reason our illustrious Fuqaha (jurists) have prohibited from hardening the grave or to build around it unless there is a dire need to do so.