The National Construction Code (NCC) requires decks to have the same level of ventilation as suspended floors. Since decks are not usually enclosed this requirement is easily satisfied. However, if the deck is enclosed around the perimeter then ventilation openings must be provided. The minimum aggregate area of ventilation in mm2/m of wall is specified in the NCC, depending on the climatic zone - less in the dry centre of the country, more in damper coastal areas. Clearance above ground is the same as for timber floors - 150mm where access under the floor is not required (eg. for termite inspection), 400mm where access is required.
Ventilation under deck