Yes but more importantly is the vents from the house.

The deck ledger usually goes on the boixer that the underfloor vents are located unless you have a basement.

You didn't mention the size of your deck, but you won't need the same calculation as underfloor venting 1sq ft / 150 sq ft.

I would say you only need enough to get some air flow to the bottom of the joists/decking.

Use the 6x14 underfloor galv. vents put maybe a couple within 3' of the coners, or where they will get the best air access. It should be easy to cut the holes in the skirt & screw them on from the exterior.

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Alter Eagle Construction & Design

If it is 18" off the ground and has spaces between the deck boards, I would not worry about it.

Excellence is its own reward!

I've removed plenty of those over the past 30 years, the deck spacing alone is not enough, you need air to circulate.

With a closed skirts you won't get the movement you need in some seasons.

Timber eating insects LOVE wet wood, and with the new acza treastment not being ground treat percentage under there it'll rot even faster.

Cut a couple of holes & screen it it'll only take a few minutes and you'll be ****her ahead.

http://www.altereagle.com/

http://decks-ca.com

http://kingofcrown.com

Alter Eagle Construction & Design