  $\mathrm{Cu_2IrO_3}$ is among the newest layered honeycomb iridates and a
promising candidate to harbor a Kitaev quantum spin liquid state. Here, we
investigate the pressure and temperature dependence of its structure through a
combination of powder x-ray diffraction and x-ray absorption fine structure
measurements, as well as $ab$-$initio$ evolutionary structure search. At
ambient pressure, we revise the previously proposed $C2/c$ solution with a
related but notably more stable $P2_1/c$ structure. Pressures below 8 GPa drive
the formation of Ir-Ir dimers at both ambient and low temperatures, similar to
the case of $\mathrm{Li_2IrO_3}$. At higher pressures, the structural evolution
dramatically depends on temperature. A large discontinuous reduction of the Ir
honeycomb interplanar distance is observed around 15 GPa at room temperature,
likely driven by a collapse of the O-Cu-O dumbbells. At 15 K, pressures beyond
20 GPa first lead to an intermediate phase featuring a continuous reduction of
the interplanar distance, which then collapses at 30 GPa across yet another
phase transition. However, the resulting structure around 40 GPa is not the
same at room and low temperatures. Remarkably, the reduction in interplanar
distance leads to an apparent healing of the stacking faults at room
temperature, but not at 15 K. Possible implications on the evolution of
electronic structure of $\mathrm{Cu_2IrO_3}$ with pressure are discussed.
