A couple of years ago the government changed the requirement for treated lumber as a result we have a different type of treatment in the lumber today.
The result of that is any standard framing wood touching treated will start rotting on contact.
To solve the problem the code is requiring a barrier between the treated and any framing lumber.
Another problem also has surfaced galvanized metal and the treated lumber is also reacting to each other, they say having the nails double dipped in galvanization will solve the nail problem, to solve the joist hangs you must put a barrier between the treated lumber and the hanger on all surfaces.
Minnesota Law is requiring a air space of 1 1/2” between the rim joist board that bolts on to the house there recommendation is to put 12-16 washers on each lag bolt as spacers to keep the treated rim from touching the wall framing.
The problem with that is a 16’ long board has 12 bolts sticking out with 144-192 washers hanging on this bolts and your trying to attach them all at once. Not happening.
Instead use 1 1/2” Galvanized steel square tubing the height of the rim joist tack it on to the rim, this will be much easier to install and provide a wider surface contact with the wall framing.
Now it time to install your decking remember your treated boards will rot wood if you are using cedar, cypress, or redwood, IPS use must put a barrier down over the top of the joists before you lay the decking.
Trex decking and other types of composite decking have different requirements for example Trex’s needs the joists spaced 12” on center, and you must space the deck board1/4” apart because the Trex board over time swell over 1/8”.
Cedar, Cypress, or Redwood, IPS board need to be sealed with a sealer or a solid color stain to keep them looking go and to keep them from weathering and firing up.
IPS (iron wood) boards are great. They come from South America, and are very strong, in the 1900 they used to make ship bottoms with this type of wood.