I got lured by discounted osb board

[StinkyAcres]

I used OSB on the outside of my coops, I'm in Southern Ontario so not that different climate wise. They're painted three coats one both sides and have held up well. For floor though I would use either plywood sealed or lay down some tiles over the OSB

Sure, it holds up for a few years. I would think most people want a more permanent coop though. My old coop had painted OSB siding and the sides that got a lot of rain lasted less than 10 years. It crumbled when I took it off this year.

 

[Lulu-vt]

I used OSB on the outside of my coops, I'm in Southern Ontario so not that different climate wise. They're painted three coats one both sides and have held up well. For floor though I would use either plywood sealed or lay down some tiles over the OSB

Do you think the moisture from under the ground will affect the integrity of the osb? It is about 20” off the ground. Currently it’s not painted or stained.

 

[Penpal]

It will last for a while. You don't need to be in a hurry to replace it. But, I would replace it with marine board.

 

[aart]

Do you think the moisture from under the ground will affect the integrity of the osb?

It could. Not all OSB is created equally.
I'd change it out now, since your walls will be on top of it, pretty hard to change out once it rots.