I don’t have the documentation for this particular stove, we got it second hand. We kept ours about a foot off the walls, but our hearth is all tile & concrete board with a 1″ air gap between the combustible part of the wall (stick framing) and the concrete & tile part. It was completely fine operating like this. I think it would have been ok without the air gap too, but I prefer “completely fine” over “ok” :). It really depends on the space you’re setting it into. It’s a great stove, we upgraded to the one in the blog post, and it is indeed better, but it’s not $2800 better when compared to the Alpiner. And the Alpiner has a simplicity to it that I really like, there’s really nothing wrong that can happen to it. Bricking it is dead simple and the path from the fire to the smoke stack is as straight as can be. I heard that it’s also 100% thick steel which is really good at retaining heat, and indeed it did better than our cookstove at being still warm in the morning.

I hope this helps, let me know if you have any other questions.