Foundations, Slabs-on-Grade, and Panel Casting Beds
This domain covers the ground and concrete surfaces that support both the finished building and the casting operation. Candidates must distinguish foundation elements (footings, grade beams, slab thickening under panels) from the casting bed itself, which may be the building slab, a temporary separate bed, or a combination. Understand how panel self-weight and construction loads transfer to the bed and subgrade, and why bed flatness and joint layout matter for panel geometry.
Key concepts: subgrade preparation and vapor retarder placement, reinforcement and dowel layout at construction joints, bed surface flatness tolerances, bond breaker application, and edge conditions where panels are cast against each other. The building slab often serves as the casting bed, so slab joint locations must be planned to avoid falling under a panel in a way that induces cracking or uneven curing.
Traps: questions implying casting beds need no structural review; confusing slab-on-grade flatness tolerances with the tighter tolerances needed for panel casting surfaces; overlooking that bond breaker must be compatible with curing compound and subsequent finishes; assuming dowels are optional at joints that will see crane or panel loads.
Rule of thumb: treat the casting bed surface as a forming surface, not a floor - flatness deviations telegraph directly into panel faces, so verify with a straightedge before the first panel. Worked example: if a 10 ft straightedge shows a 3/8 inch gap under a bed intended for architectural panels, that deviation will likely be visible after erection and should be corrected or the affected area avoided for finish-critical panels.