Depth of #foundations

Foundation #depths for #decks and other accessible exterior #platforms can be less than the minimums in NBC Table 9.12.2.2. if the deck is not more than one storey and not more than 55 m2 (590 ft.2) in area, the distance from the #ground to the underside of the #joists is 600 mm (2 ft.) or less, the deck does not support a #roof and its movement will not affect the structure it serves (Figure 9.12.-6).

Quoted from Illustrated Users' Guide -- NBC2015