A pre-cast concrete base (or footing) is placed on top of the engineered fill and carefully leveled.
The footing serves as a stable base for the steel jack post, keeping it vertical and distributing the weight bearing on the post across a broad area of soil. The engineered fill base underneath the footing provides solid support that won’t shift, settle, or be affected by soil moisture. Some building codes may require a poured concrete base rather than engineered fill.
By the time the weight is distributed through the pre-cast base and the fill, the bearing stresses have dissipated to approximately 10% of the stresses at the top of the post. Even if you have weak supporting soils, you can be assured that the weight of the building will not exceed their bearing capacity.