I Need To Enlarge My Deck.

[HazMatt-SKO]

Cool beans! Thanx for the thoroughly comprehensive reply!!

2x2s are floating. Planks are 3/4" thick x 6" wide x 6' long. Bolt holes were slathered with sealant before and after insertion. Deck currently has 4 coats of spar urethane, but will get more. I used rubber weatherstripping sandwiched between the roof metal and the wood hatch frame, then covered the joins with liberal amounts of sealant (3 separate coats totaling about 3/8" thick). The 'slo-mo Peter Pan posts" [emoji2] will be installed when I add my awning storage box to the deck.

I used to be a framing carpenter, once in my somewhat eclectic employment history. Nothing that was expected to experience much in the way of vibration and weird torsional stresses, so very much appreciate hearing what all the nuts and bolts are, and where to put 'em!

The "fancy cutting" refers to my original vision of the joists running perpendicular to the long axis, with two rows of bridging.
To have them supported by metal, the underside would have to be cut to accommodate the roof's curvature, and that would take either 2X6 or 2X8s to leave enough loadbearing meat behind.
Not doing the Happy Dance at that concept!

I bought 12' planks (lower per foot cost) and cut them to 6'. Not sure what you mean by 'fancy cutting to accommodate" -- the 2x4 joists are 54" apart, which leaves the bottom of the deck boards about 1 3/8" above the roof metal.

Running lengthwise would require a lot of stringers.....my 240 pounds would deflect the planks more than I wanted on a 22" span, so my stringers are 18" on center.....they're suspended about 1/8" above the roof until stepped on.

You make a good point on centers' spacing, one I hadn't considered, so thanx for that, too. Thus far, I've reckoned on building my posts up off the ribs, which are a RCH less'n 29" apart.

Thinking I gotta do some more thinking about this... [emoji848]