An attached deck hangs half its weight on a single board: the ledger, fastened flat against the house band joist, from which the deck joists span out to the beam. Because that one connection carries so much, the code prescribes it in detail — 2021 IRC Table R507.9.1.3(1), also published as Table 5 of the AWC deck guide (DCA 6), tabulates the on-center spacing of 1/2-inch lag screws or thru-bolts by deck joist span, for a ledger of southern pine, Douglas fir-larch, or hem-fir on a 2-inch nominal SPF band joist at 40 psf live plus 10 psf dead.
The three connection details trade convenience against spacing: lag screws must fully penetrate the band joist and demand the tightest spacing, thru-bolts allow the widest, and thru-bolts with up to 1/2 inch of stacked washers can bridge a furring gap at a spacing penalty. Longer joist spans put more load per foot on the ledger, so the required spacing tightens as the span column grows — an 11 ft joist span reads from the 12 ft column, and spans over 18 ft need an engineered connection.
Placement is prescribed too, per Figure R507.9.1.3(2): fasteners stagger between a top and bottom row, at least 2 in and at most 5 in from each ledger end, 2 in down from the top edge and 3/4 in up from the bottom. Flashing (R507.2.4) and the lateral-load connection (R507.9.2) complete the code picture around the same board.