A spring-loaded post extension for resilient support of ceiling grids during seismic events. The post extension includes a fixed cylindrical housing and a movable spring-biased assembly, axially coincident therewith. The housing is connected to the side of a fixed support post. The assembly includes a support tube extending partly within the lower end of the cylindrical housing. The bottom of the support tube is connected to a ceiling grid junction. A threaded rod has an upper portion extending above the upper end of the housing, and a lower portion extending through the housing to connect to the top of the support tube. An exterior spring fits over the upper portion of the rod, and an interior spring fits over the lower portion of the rod. Nuts on the rod provide means to tension both springs into slight compression, defining a spring-biased normal position for the support tube.