The paper describes a case history -related to the Line 9 excavation in Barcelonawhere compensation grouting was initially proposed to minimize the movements of the buildings close to or directly above the tunnel alignment, some of which have piled foundations. Unexpectedly, the ground settlements due to the pre-conditioning stage of the compensation grouting became very significant leading to some light damage to one of the buildings. Eventually, the decision was taken to stop the treatment. Grouting-induced displacements are compared to the movements produced by tunnelling that were very limited. The paper concludes with some considerations concerning the suitability of ground treatment in the context of carefully executed tunnelling operations.