Sistering or other solution for deck joists?

[Red Squirrel]

I don't like how they have the joists going right into the wall like that, and I do wonder what they are fastened to inside, and how. It would be impossible to get them on joist hangers unless the brick was somehow put in AFTER the deck, which I doubt. Brick alone is technically not structural so I hope they're not just laying on top... I'd be tempted to redo the whole deck and put a proper header board at the wall with bolts going into the rim joists. If you happen to hit a joist then a lag bolt is fine, otherwise use a normal bolt so you can go and put a big washer and nut on the end at the rim joist on the inside. Once you have the header in place then you can use joist hangers for the joists of the deck. Use the proper nails rated for hangers, they are stronger. When putting in the bolts you probably want to mark where the joists will go as well so you don't put a bolt in that location.

If it were not for the weird way it's fastened to the house I'd go ahead and just sister joists but I think a rebuild is better. For sistering, when you put glue, do upside down Us or Vs. That way if water gets between it will flow out. But ideally they should be screwed on tight enough that water won't be able to get in. I always use clamps to bring it as tight as possible before putting in the screws.

But yeah I would just lean towards redoing it at this point. Some of the major lumber might be salvageable but really may as well just use all new.