Hi community,

We’re in zone 5, hot dry summers, very low humidity right now, 10-20 by day, 20-30 by night.  Winters are rainy/snowy here.

My main question: how soon after cement is poured for beefing up foundation walls, can a crawlspace vapor barrier (over the dirt crawl space, but attached to those cement foundation walls) be installed without negatively impacting the curing of the concrete, and without sealing in moisture excessively.

We are replacing crawl space siding in some areas, and putting cement under that  (a portion of the foundation is pier and post, and they are transforming that into a more continuous base for the siding — cement-filled sand bags, concrete blocks, etc. to make it a more continuous foundation and less inviting to pests and moisture).

Above the concrete/cement, there will be PT sill plates (with butyl tape as capillary barrier in between the cement and plate), framing, and a wall assembly of 5/8 plywood, drainwrap, foamular XPS, rainscreen, then metal siding (Corten).

Planning to put 12 mil vapor barrier from Crawl Space Ninja, using butyl tape and christmas tree fasteners, on the cement walls 3″ below the sill plates.  

How soon after the cement work is done, can the vapor barrier be installed onto that cement, without negatively impacting curing or trapping moisture (weather is very dry now so we want to maximize the drying process).

This will be a vented crawl space with a small exhaust fan which turns off in cold temperatures, and an auto-vent that closes at 40 degrees and opens back up at 70.

There is a basement in that same area, and part of what is being rebuilt (post-remediation) is the dividing wall between basement and dirt crawl space.  The bottom of that will be concrete.  It will be easier to install the vapor barrier before the plywood portion of the wall is built (crawl space is very short but the basement is tall), so this might need to be done after the cement portion of that dividing wall is built but before the wood portion (vapor barrier will attach to the cement portion).

How long is it best to wait post-cement-work before installing that vapor barrier attaching to the new cement?

Thanks!