ninja_yodeler wrote:to the best of my knowledge hearth fires have a soak value of 25 so you need at least 26 to damage them, however that damage would be tiny you want a lot higher than that to get it done in a reasonable time

Damage is calculated based on your score of sqrt(str). A damage soak of 25 is actually the value of a palisade, and requires 400+ str to damage with a sledgehammer.
I've heard 36 str is enough to hurt it with bare hands, that puts the soak at 6. It might be that the soak is 5 and people think you need to deal a full point of damage per tick to do anything. Either way, If that's true, 16 str to hurt it with a pickaxe, 25 with a stone axe.
Mind you though, it has a helluva lotta health. So bring water.