This project involved renovating a turn of the century farmhouse and adding on to it. This room was part of the original structure and you are looking at plain pine boards, circa 1920 or so, butted up to each other.

When doing new construction to achieve this look...do you apply paneling over sheetrock or do you even need sheetrock?

I would always recommend sheetrock, drywall, or greenboard (especially for bathrooms) just to button everything up. I'm not a pro but have worked on many projects and we're getting ready to put wide plank panels in our bathroom. Good luck!