I am getting ready to build a pergola and am planning to stain it white using an opaque stain. I will be able to stain the components before building the structure for added protection.

Do I need to use pressure treated lumber if I am planning on staining it? What's the best type of wood to use in the application?

And while we're at it, can anyone suggest a preferred opaque stain product?

Any other thoughts, suggestions or tips?

I would go PT or maybe cedar because even n opaque stain isn't 100% water proof for ever. I like this company but many of us have our favorites. Wolman Deck and Fence Stain

I am right now trying a new(er) latex stain from Sherwin Williams,Deckscapes.

It says to test new wood for absorbency by putting a drop of water on different areas and see if it beads or gets readily absorbed.

New wood will most likely bead and require 1-2 weeks to weather out before using this product,being that it is water based.