Running a Dryer Vent Under a Deck. Running a dryer vent underneath a deck is one solution when the exterior vent is in the immediate area of the dryer vent.Click to see full answer. Similarly, can you run a dryer vent under a deck?Dryer vents always seem to be located right where my clients want their decks. Dryer ducts often run between the floor joists and terminate through the rim joist — right where most decks are connected. So yes, there are some concerns. Dryer fires generally occur when lint builds up in the vent (Figure 1).Also, can a dryer vent be vented down? Above: a clothes dryer exhaust vent installed in a mobile home can be vented down through the crawl space and outside through the skirting wall, but must never be vented to terminate right in the crawl space. Considering this, do decks need ventilation? It is very important that there be adequate and unobstructed air flow under the deck to prevent excessive water absorption. Improve drainage or grade flat areas where standing water may gather. For decks with limited ventilation, six inches of clear ventilation is required.Do you need air flow under a deck?If airflow is restricted on one side, the board(s) will expand/contract unevenly, which is what causes buckling, warping, and twisting. We always recommend at least 18 inches of open space beneath the joists because this allows air to pass unhindered and unaltered below the deck.