Shore Tower Design Calculator

Total Design Load responds only to Slab Thickness, Concrete Unit Weight, Construction Live Load, and Form Dead Load -- it never depends on Shore Capacity or Bay Size at all, since those two inputs only decide how the same fixed load per square foot gets divided up among posts, not how big that load is. Shore Capacity is the input that swings the shore count the hardest: at this calculator's other defaults, a light-duty 500-lb shore forces 225 shores into one 20 ft x 20 ft bay at a cramped 18 in spacing, while a heavy-duty 30,000-lb shore needs only 9 shores at a 162 in spacing -- a 25x range in shore count from Shore Capacity alone. Bay Size behaves roughly quadratically on Shores Per Bay, not linearly, because it grows the shoring grid in both directions at once: a 4 ft bay needs only 4 shores, but a 40 ft bay -- 10x the length -- needs 81, about 20x as many, since doubling bay dimension roughly quadruples the enclosed area that needs support at a fixed post spacing. Practical Spacing rounds DOWN to the nearest 6 in increment from the calculated maximum spacing, but it never reports a spacing below 12 in -- shore posts and their cross-bracing physically cannot be packed tighter than that on a real deck. For most inputs the calculated maximum spacing sits above 12 in, so that floor never engages and Shore Utilization lands under 100%, typically in the 70-100% range.

But when the load is heavy enough -- a thick, dense slab; a light-duty shore; a high construction live load, especially in combination -- the calculated maximum spacing can fall below 12 in. When that happens, the 12 in floor forces Practical Spacing WIDER than the load actually allows, and Shore Utilization reads above 100%. That is a real overload, not a rounding artifact: the shores as spaced cannot safely carry the load. ALWAYS check Shore Utilization before using the displayed Practical Spacing -- at or below 100% it is safe; above 100% it means this shore capacity and load combination requires either a higher-capacity shore, a reduced design load, or an engineered non-standard spacing tighter than 12 in (which this calculator does not model).