Compaction of the core of plasterboard is one of the limiting phenomena for its mechanical performance. This mechanism is studied herein in an indentation test. A cylinder made of foamed gypsum is indented in-situ in an X-ray lab tomograph with a sphere of millimeter radius. The reported experiments show that foamed plaster displays a sharp transition between an undamaged state (with linear elastic behavior) and a compacted state with collapsed porosity under the indenter. Tomographic acquisitions of the sample under load associated with a global version of Digital Volume Correlation allow displacement elds to be measured at dierent load levels. However, because of the heterogeneous nature of the indentation test, a ne spatial resolution of the displacement elds is required to measure the strains at the crush-* Corresponding Author. Fax: +33 1 47 40 22 40