Lee started laying down the underlayment flooring in one of the upstairs bedrooms. We are using 1/2″ CDX plywood. We plan on having wood floors so we needed to use plywood instead of OSB because of its superior nail holding capability. Putting down the underlayment also is going to make the upstairs floor stiffer. We are using glue and screws to help prevent squeaks.
We originally were going to use a product called DAP Subfloor 7000 (because it had low VOC emissions) under the CDX. We must have gotten a bad batch of it at the store because it was rubbery and non adhering. So we brought it back to the store and ended up going with PL Premium. Its a polyurethane adhesive which is basically not suppose to off gas. It seems to have better performance in every way compared to the other product. It also had less warnings (like brain damage) on it compared to the DAP. So far Lee seems pretty pleased with it.