Deck Advice for Sealing Concrete Slab Edges Against Exterior Wall
Tore out a pre-existing 20 year old wood deck that was deck boards nailed to prone 2x4's laying on a concrete slab. The edge of the concrete slab has about a 1" or less gap around the edge between the house and the slab. The previous homeowner seems to have run shingles down to the level of the slab and it looks like wood joists for this protruding room are just sitting on the poured foundation. (Hard to tell through gap right now.)
When I dug into the proper way to seal a concrete slab it mentions backer bar and sealant along the surrounding gap. However, this usually assumes you're sealing concrete to concrete in most cases. The other side of the gap appears to be wood / joist / exterior wall. My gut says I should cut back the shingles to the level that I expect the new deck to be at, and try to slip flashing in there and seal the flashing. Or add some kind of waterproof wall material to the exterior wall before attempting to seal it.
I googled a bunch before posting, but I can't find a good recommendation for what to do when trying to seal a concrete slab gap against a non-concrete exterior surface. Any advice would be appreciated.