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It meant that Burnham could use Root’s floating grillage for foundations without having to worry about catastrophic settlement.

Once complete, this grillage of steel would be filled and covered with Portland cement to produce a broad, rigid raft that Root called a floating foundation.

Workers laid foundations of immense timbers in crisscrossed layers in accord with Root’s grillage principle, then used steam-powered derricks to raise the tall posts of iron and steel that formed each building’s frame.

On top of these they laid a grillage of steel, then filled it with cement.

All timber grillage and the tops of all piles should be kept below the lowest water level, and be capped with concrete or stone.