The potential energy surface for the gas-phase SiH4+K-->SiH3+H-2 reaction and its deuterated analogs was constructed with suitable functional forms to represent the stretching and bending modes, and using as calibration criterion the reactant and product experimental properties and the ab initio saddle point properties. Using this surface, the rate constants were calculated with variational transition-state theory over the temperature range 200-1000 K, finding good agreement with experiments. We also provide a detailed analysis of the kinetic isotope effects and a comparison with the scarce experimental results.