Deck and pergola planner

Framing — species and joist spacing pick the column of DCA 6 Table 2; the joist span L runs from the face of the ledger to the face of the beam, and the overhang past the beam is limited to the lesser of Table 2’s allowance and L/4. Beam chooses 2-ply first (then 3-ply) and adds posts until the beam span is within Table 3A for that joist span; the beam may run past its end posts by up to a quarter of its span (Figure 3).

Footings — Table 4 gives the maximum 6x6 post height and the footing size (round, square, thickness) for the beam span and joist span. Footings bear at least 12" below grade and below your frost depth.

Ledger — Table 5 spacing for ½" lag screws or through-bolts into a 2x band joist, staggered.

Decking — the joist spacing is checked against IRC 2021 Table R507.7 (5/4 wood 16" square to the joists or 12" at 45°; 2x wood 24" / 16"; composite per its label).

Guards are added when the deck is more than 30" above grade (IRC R312.1): 36" high, posts at most 6′ apart with 1,800 lb hold-downs (DCA 6).

Pergola — posts, two doubled beams and rafters over the deck. There is no prescriptive table for an open pergola roof, so its members are sized with the same deck tables (40 psf), which is conservative except under heavy snow; check snow load, uplift and bracing locally.