Or in you case, where its only on the first floor, you will have to rate to the underside of the floor decking above AND fire rate the ceiling as well (if there is livable space above that is not associated with this ADU/STR).

In this scenario the underside of the roof deck would be ventilated to address drying concerns.   

Todd one straightforward strategy for addressing damp crawlspaces is to apply --closed cell-- (not open cell) spray foam to the entire underside of the flooring deck of the home, provided you have some sort of sheathing or substrate below the finished flooring.

What's supposed to happen is that the sink is held in place by little clips on the underside of the countertop and sealed to the granite with silicone caulk.

I did this in half a day with all seven windows in that unit.I cut a piece of 1X4 and mount it on the underside of top side of the recessed window frame, using three 2-3/4" Tapcon screws from the bottom driven into the concrete blocks. 

We later found burn marks on the underside of the upper kitchen cabinets and candle wax in the carpeting.

The odor then goes into the crawl space via the gaps and voids in the unfinished underside of the wood.

In the attic if you see discoloration on the underside of the roof it may have a leak.

Years ago, in NYC, I used to hide a key in a magnetic key box outside attached to the underside of metal stairs. 

These planks that looked pretty nice got pulled up and showed an underside that looked, felt, and smelled like cat piss jelly -  thick.Now there is a layer of 12x12 linoleum glue down tile that was underneath the LVP.