which I bought materials told me to go with Douglas Fir lumber over pressure treated (they sell both) but to use Deck Wrap.



I covered the ledger boards, the tops of all beams, joists and stringers (and the bottoms of stringers) and the sides of the rim joists with Deck Wrap.

According to the supply place, once you cut pressure treated lumber it loses most of its protective properties unless you cap the ends and treat again. They swear by Deck Wrap and their deck install guy says he will not build a deck without it.

I personally know nothing, but, they are the experts. so I went with their advice.