[Crowbob]

I have the same situation. I decided a ceiling under the entire deck (mine is 17x23 or so) would be a perfect hideout for birds, critters, bugs, leaves, etc. So, I’m thinking a couple of panels of sloped corrugated fiberglass/plastic panels suspended by chain would allow the occasional cleaning, probably annually.

At least some of the area under the deck would be dry.

I’ve considered long wedges under each joist but wood would crack and/or split over time.

I haven’t done anything, yet.