Hollowcore Plank Selection Calculator

The span/load table is simplified from the hollowcore section capacity design aids in the PCI Design Handbook: Precast and Prestressed Concrete, 8th Edition (MNL-120-17), published by the Precast/Prestressed Concrete Institute, cross-checked against published manufacturer catalogs. The Fire Rating output is a rough equivalent-thickness estimate in the same spirit as the fire-resistance tables the International Building Code (IBC) references for concrete assemblies -- it is not a substitute for a project-specific, code-official-approved fire rating, which depends on aggregate type, cover, and the exact assembly tested.

The calculator still displays a Recommended HC Depth -- it falls back to the deepest table row (16") even when that row doesn't actually satisfy your span and load. This is easier to hit than it sounds: at this calculator's own default Superimposed Load (80 psf) and Composite Topping (2 in), the fallback already triggers once Clear Span reaches 39 ft, and at the calculator's maximum 60 ft span it triggers unconditionally, regardless of load or topping. The only way to catch this is to check both Span Utilization and Load Utilization: if either one reads above 100%, the displayed recommendation is infeasible and you need a deeper custom section or a different structural system.

Because the table lookup only reselects a different plank depth once your load (or span) crosses into a different row's capacity range. A modest load increase that still fits the currently-selected depth changes Load Utilization but leaves Piece Weight unchanged, since the selected depth and its associated self-weight haven't moved.

Clear Span has the largest measured effect, since piece weight is a direct product of total dead load per square foot, Plank Width, and span length. Plank Width moves it by the same direct proportion, while Superimposed Load itself doesn't directly enter the weight calculation at all — it only matters indirectly, through which depth gets selected.

Yes, occasionally — Composite Topping Thickness grants a small capacity bonus (about 4% per inch) to every table row's adjusted span and load limits, on top of adding roughly 12.5 psf of its own dead weight. In borderline cases that bonus can be enough to qualify a shallower plank than a topping-free comparison would select.