Sheathing to concrete gap fill
Have a semi odd scenario.
1950’s house, Zone 4A for reference
North facing alcove front porch
Originally the siding was installed and then the concrete front porch was poured. I am removing the vertical T&G siding as part of a larger renovation and to access the termite damaged rim. Plan is to replace the rim and any other damaged framing then install 7/16 Zip over the board sheathing and reside with a new Vertical T&G over a rain screen. I’ll install metal flashing from the Zip to the concrete (Risinger recently did this same detail in a video). The rim will be sprayed with foam on the inside in the fall.
My question is thus:
The old siding was 3/4 thick and there was no gap between it and the concrete. Once the 7/16 Zip is installed there will be a 5/16 gap between the sheathing and the concrete. There will be no airflow.
What should I fill this gap with?
Should I leave it open?
Is it a bad idea to put OSB into this space?
I could put something like a 3/4 PT into there that I coat with Copper Napthenate to discourage future bugs and then tape the joint to the Zip.
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