Paint OSB subfloor to protect from rain during slow construction?
The house I’m building in central Arizona has a subfloor of 23/32″ Norbord Truflor OSB on i-joists over a ventilated crawlspace. I’m building by myself and very slowly, so it might take me three months before I have walls and a roof. In the meantime, I’ve considered protecting the OSB from weather by painting it with Rust-Oleum Porch and Floor, which is designed to withstand sun and occasional puddles of water. On average, my location will get 6 days/1.2 inches of rain in March, 3 days/0.7 inches in April, and 2.1 days/0.3 inches in May. The Truflor has an Exposure 1 rating to withstand normal delays in construction without affecting its structural properties. I tried tarps to keep the subfloor dry, but they failed miserably.
Does my dry climate compensate enough for my slowness in building that the OSB should endure the time it will take me to get it out of the weather?
Would painting the OSB create any problems because it will only be able to dry from the underside when it absorbs moisture from the crawlspace air until I seal the undersides of the i-joists with foil-faced polyiso?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part