Ah... I see. Well, you were asking about your run, so I was talking about my run, too

The run uses 2x4's and 4x4's. The blue siding on the coop is OSB. I used Behr waterproofing stain on both, the difference is that I used the solid color (blue) on the coop, and the semi-transparent stain on the run, because I was going for the natural look there - wanted the grain in the wood, and a dark stain to look more like tree bark. I didn't pre-treat anything before staining, and everything seems to be holding up fine so far (5 months).