Why would you want pressure-treated wood?
Pressure treatment only serves a purpose with continuous ground contact (i.e., installed in soil).
If it is above ground (approximately 150mm air gap) but can get rain on it, place a strip of tar paper/underlay on top so the wood never gets wet.
If the task is to support a wooden deck, for example, the joists will last for at least three rounds of decking because the joists themselves never get wet or even moist thanks to the tar paper/underlay. And this is regardless of whether they are pressure-treated or not.
Like this
https://www.byggmax.se/syllisolering#913=105680