Flat Roof Option
Similar to the floor, the roof slab is cast in a single placement with no construction joints. This method results in a watertight slab that eliminates the possibility of substances entering the tank and contaminating the contents. The roof slab is column-supported with typical spans in the 30-foot range each way. Slab thickness is approximately 8 inches. Roof shoring is placed immediately following the column and column footing placement to minimize construction time. Post-tensioning tendons are placed orthogonally as in a typical two-way suspended slab and are "stage stressed" in the same manner as the floor slab tendons. After the tendons are stressed, the shoring is removed through access hatches.
Dome Roof Option
Column-supported flat roofs are often chosen for buried tanks or where a less visible tank is desired. A cast-in-place concrete dome is an efficient option for circular tanks where a flat roof is not required