I attended a wood flooring job where a slab took moisture from a plumbing failure. There was poly sheeting on the slab, 12mm ply then 13mm overlay solid timber. The whole thing buckled like buggery. So there are definitely points which poly cannot withstand. As JD always advises- see what the warranty says!
The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher