Shielding optimization for the Compact Ignition Tokamak baseline test cell building design is performed to minimize the cost. The design is based on iterative calculations using one-dimensional SN models calibrated to the results obtained by coupling a three-dimensional Monte Carlo model to a two-dimensional SN model. These sophisticated models remove most conservative factors in the baseline design. When a low-sodium concrete is used as the base material, the boron concentration and the thicknesses are reduced substantially. The optimal configuration that satisfies all the shielding and structural requirements shows a cost reduction of ∼14% ($4.1 million) relative to the baseline design.