Untreated wood vs pressure-treated

[useless]

In another thread it is claimed that you absolutely should not place untreated wood against pressure-treated wood. Can someone explain why this would be particularly harmful?

https://www.byggahus.se/forum/threads/altanprojekt-praestgard.319610/page-3#post-3011508

 

[Pagno]

In another thread it is claimed that one should absolutely not put untreated wood against pressure-treated wood. Can someone explain why this would be particularly harmful?

[link]

Untreated wood has better moisture transportation in the fibers.
Heat-treated/pressure-treated wood has much poorer moisture transport.
If you lay a treated decking on untreated framework, the contact surfaces do not dry as well as if you lay untreated against untreated.

You could say that the impregnated deck is a dishcloth that constantly releases water towards the untreated wood.

It works perfectly well to place untreated against standing posts of pressure-treated, as long as the posts are not absorbing water from any direction.

Best regards, P-A

 

[useless]

But you have that problem even if you cover the timber with paper, masonite, plastic, a steel beam, etc.?
If you have such a construction, it probably doesn't help to separate the untreated and impregnated timber with paper or similar?