Columns installed without footings are generally a concession to a quick job and have no basis in sound building practices. Both U.S. and Canadian national codes call for footings on all in-ground concrete columns.
U.S. Boca 1815.0 Canadian national bldg code table 9.4.4.1
Stable column foundations with footings are particularly important where one side of the new structure (deck) is attached to stable, unmoving structure (house). With one side of the deck pinned to the house, any significant movement of the outlying columns will cause twisting and stress in the supported structure. In colder areas, the commonly held notion that frost must get below the column to lift it (frost heave) is erroneous. Columns with footing are much more resistant to washout in hilly or flood prone areas, often meaning the difference between a minor landscaping Job and replacing the whole deck. In out-buildings, where doors and windows are present, a stable unsinking foundation eliminates pinched, binding doors and jambed unusable windows. Columns with footings, allow for future deck conversions to a screened-in porch or glassed-in sunroom because of their stable, load handle capabilities.
