We report here the first layer rigidity study which has been performed on layer double hydroxides (LDH's) having a fixed-host layer. The LDH materials studied have the chemical formula [(CO3)(0.195(1-x))Cl-0.39x]:[Zn0.61Al0.39(OH)(2)], 0 less than or equal to x less than or equal to 1. An inter-layer rigidity parameter of p=4.84+/-0.06 was determined for these compounds from a fit of the standard version of the discrete finite layer rigidity model to the composition-dependence of the normalized basal spacing measured using X-ray diffraction. This result validates the previous results obtained from the more complex, variable-host layer LDH materials.