We are building a deck, and the whole time so far we have been planning on attaching the deck to the house via a ledger board. After stripping the siding and insulation foam board, we discovered that all that remains is ~7/8" sheathing attached to the ends of the floor joists (I-beam shaped, spaced a little more than 19" on center). As far as we can tell, this is insufficient for attaching the ledger, no matter how many lag screws and such we use. Is this true? If so, how can we solve this?
Some of our constraints: - Making the deck free-standing would be difficult / impractical at the height we have to work with. Our current design has the beams at the same level as the joists. Putting beams below the joists to make a cantilever toward the house would require making the beam either very short or partially under grade. - Our basement is finished, so we can't easily add structure to the floor joists from there. We could cut away some of the sheathing, but we're a bit concerned this could increase the risk of water getting in through the seams.