In cases of minor flooding I have seen a plywood and solid wood subfloors dry out on their own, as long as you take a board of two of the damaged hardwood off to expose them to air. It’s funny because in a lot of cases with non-OSB subfloor we just tell the client to wait 4-6 months, or until the heat comes on. The subfloor boards or plywood dry out, and miraculously the hardwood in a lot of cases will settle back into place. But OSB will remain permanently swollen, and both the hardwood and the subfloor will need replacement. At great expense.
The Virginia tech study concludes that once OSB goes through several normal indoor seasonal moisture cycles, the flooring tends to remain out of the original position, so more permanent gaps can be expected. It’s not really fair to complain to the osb industry, after we have mistakenly wet their product. But wait there’s more. To their credit the OSB industry is improving on the manufacturing method, and have added a water resistant phenolic resins. In an advertisement I just saw in a home building magazine, the caption reads “Why use AdvanTech ® ? (a new water resistant OSB), because I build all my houses outside.” You can visit their web site at www.huberwood.com and draw your own conclusions. This new and improved OSB maker admits that the old OSB was having some problems. Now, are all contractors using this new OSB material and why did we all settle for the older OSB? WELL, GOOD OLD PLYWOOD HAS BEEN AVAILABLE ALL THE WHILE.
The use of a water resistant resin is the second major improvement in the osb industry, but the Louisiana Pacific co. is still burdened under tens of millions in class action claims from the osb sheathing products they sold from 1984-1997. This was the first generation of osb. A really checkered past.
Plywood is made of plys of real wood with a waterproof adhesive. I generally get about 15 years use from the plywood sheet I expose to all weather in the back of my pick up. You figure it out. I use always exterior grade plywood for all my subfloor, and underlay uses.
Oh, by the by a typical OSB panel has about 4 times the amount of resins that a plywood panel does, thus has an increase in off gassing due to the greater surface area of resin exposed. But the NEW OSB claims to have ALMOST no urea formaldehyde in the composition. This is a relief, but what was in the old stuff?