The most important step in raising concrete is not the actually raising of the slab. Instead, the critical component is making sure all the voids under the concrete are filled after it has been raised. This includes the voids that were present before the slab was raised, as well as, any voids created during the raising process. Too many contractors doing our work will raise the slab on pillars or columns of material (whether a traditional slurry or the newer poly foam products) and leave voids in between these columns. Imagine holes that are 5 feet apart with 18” diameter pillars underneath them, for example. There will be a large void, or cavity, between these pillars that is not filled in. A job that is done like this (i.e. raised but not stabilized) will fail. To insure a job that lasts, a contractor must not only raise the slab but also fill the voids created during the raising process.