The kagome metal ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ hosts an intriguing interplay between charge-density-wave (CDW) order and superconductivity that is highly sensitive to lattice distortions. However, determining the specific roles of the in-plane $\left(A_{1g,1}\right)$ and out-of-plane $\left(A_{1g,2}\right)$ symmetric strain channels has been hindered by their intrinsic mixing in conventional piezo-based experiments. Here, we combine in-plane uniaxial strain with direct $c$-axis compression to independently access and disentangle these symmetry-resolved responses in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. We reveal that $c$-axis compression drives a substantial, linear enhancement of the superconducting transition temperature $\left(T_c\right)$ alongside a suppression of $T_{\mathrm{CDW}}$. The tuning efficiency of this out-of-plane deformation acts with an opposite sign and far exceeds that of in-plane strain, demonstrating that $c$-axis lattice control dictates the phase competition. Furthermore, by isolating the pure elastoresistivity coefficients, we find that the out-of-plane cross-coupling coefficient $\left(m_{13}\right)$ is comparable in magnitude but opposite in sign to the in-plane response $(m_{11}+m_{12})$. Unlike the sharply peaked in-plane response, $m_{13}$ exhibits a distinct, order-parameter-like onset across the CDW transition. Our results establish that out-of-plane lattice control plays a dominant role in tuning the intertwined states in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ and provide a general pathway for resolving strain-coupled electronic responses in layered quantum materials.

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• Charge density waves
• Elastic modulus
• Kagome metal
• Low-temperature superconductors