Water-based latex acoustical sealant (caulk) in crawlspace / under mud sill?

finePNW | Posted in General Questions on August 10, 2023 07:22pm

I am in the Seattle, WA area (Climate Zone 4C) and making a last minute scramble to convert a normal addition project into a high(er)-performance addition — with gung-ho air sealing and continuous exterior insulation.

Is the water-based latex USG Sheetrock Acoustical Sealant OF for use between mudsill and sill gasket or in the crawlspace/basement in general? Their spec sheet cautions against use in “wet” areas, so I am leaning towards “no.” However, the sill and rim joist will have aluminum faced polyiso exterior insulation and will be flashed, so bulk water shouldn’t be a problem.

Should I be concerned about this in terms of “wet”ness? Will the generally moist nature of the stemwall/crawlspace/mudsill area cause any issues with durability or, worse, mold?

I suppose they also indicate discoloration when used on copper, and the mudsill is treated (probably with a copper concoction); I’m not worried about color, but hope it is not an indication of long-term chemical incompatibility.

Here is the caulk — installation guide and submittal sheets attached: https://www.usg.com/content/usgcom/en/products/walls/drywall/sealants/sheetrock-acoustical-sealant.html

UPDATE: I decided to just go with Dynaflex 230.