Do I need a barrier for pressure treated wood when it touches concrete?

You really should consider using a standoff post base—it's basically a must if you want to prevent rot in the future. I’ve been watching a lot of DIY projects, and those bases are commonly recommended because they keep your posts off the ground.

I agree with others here! Not only should you have pressure treated wood, but it’s also a good idea to use ground contact rated wood. Holding the post off the concrete with a base is key, plus treating any cut ends with wood preservative will definitely help too!

It's crucial to use pressure treated wood when it comes into contact with concrete, as concrete can draw moisture and cause the wood to rot over time. I recommend using a standoff post base, like a Simpson base, to keep the wood off the concrete. That way, you give your pillars a better chance to last longer.