Materials for subfloor

[bjoho]

I have some 21x145 mm that I am considering using for the subfloor. The wood is actually exterior cladding where one side is rough-cut. It is not tongue and groove.
Are there any obvious reasons NOT to use the wood for the subfloor? If not:
-Should I treat the wood in some way? Oil or anti-mold or the like?
-Since the wood is not tongue and groove, should I seal between the planks? With what?

I am building a small vacation house that is not used during the winter.

 

[Max31]

Hello

We did the same thing when we extended my parents' summer cottage. We put a wind barrier over so the wind wouldn't blow directly into the insulation; the cottage is on pillars.
However, I cannot say if there is any "risk" with this method of making the subfloor.

/Max