New techniques that can control Casimir forces in nanosacle structures may soon ensure the physical realization of switchable Casimir-force devices. In order to provide useful insights into the behaviour of this class of switches, the idea of Casimir-force actuation window has been proposed here to assist in the design of such switches. The influence of surface effects including residual surface stress and surface elasticity on the pull-in parameters of Casimir actuated switches has been demonstrated. These effects, together with other currently known difficulties due to uncertainties such as surface roughness and trapped electric charge may hinder the realization of this class of devices. An Euler-Bernoulli beam model has been employed to demonstrate surface effects in a nanocantilever switch, and numerical solutions employing a finite difference approach have been obtained for the static bending of this switch. The results demonstrate that surface effects play a significant role in the selection of basic design parameters of Casimir actuated switches, such as static deflection and detachment length. Threshold value of residual surface stress is also studied for these switches. The predictions reveal that exclusion of surface effects in Casimir-force actuation window may result in non-functional switch designs.