wanting to make an outdoor sauna.. what wood?

[treeroot]

Looking to mill up some wood to make an outdoor sauna. Something like in the picture attached.. I have access to spruce, tamarac or apsen for wood. I would prefer to mill the wood, not buy.. So that's what we have in our area. Oh and there is some balsm fir around, but not much.

I was thinking tamarac, but I think it might bend and twist each time you use the sauna due to the moisture.

Any ideas?

 

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What you have at your disposal buddy.

 

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Pine.