I'm in the process of building a small cabin I wanted to use the T-111 pressure treated as the siding but I wanted to run them side ways and where they meet I wanted to run slats up & down. The reason is I'm using 10' studs for my outer wall and if I run they up & down I will have a seam at the top & I do not like how that looks. I also wanted to paint them. Can you give me any pros & cons on running them sideways? If this is not a good way of doing it I can always put siding over it after time. Thanks

If you run them sideways you'll have 2 seams! If you use them the way they're designed to be used, the seam an be either 2 feet down from the top, or 2 feet up from the bottom. I'd use the lower seam, and make something good out of it by using a feature strip, rather than the cheesy piece of flashing that you usually see.

I think the biggest problem with using T-111 horizontally is that water will be retained in the grooves, and could rapidly begin to de-laminate the plywood.