If you do a search, you will find many threads on this topic.

You'll find some posts describing how my DH did our shower and tub surrounds. He used Hardibacker (cement board) for the shower/tub walls, and then Hydroban rolled over it. The Hydroban was very easy to apply according to DH (he did 3 coats).

I believe either way is an option, but I am sure our resident experts will weigh in as well (Bill V., mongoct....).

I think it's best to have the waterproofing as close to the finished surface as possible, so that means a surface applied waterproofer, like Kerdi, Hydroban, Redguard, etc.

Thanks to both. Terriks, I'm inclined to agree - a vapour barrier would seem a last resort, being right next to the wood you're trying to protect.

Answered on your other post.