It’s less formal than raised panels, however is correct reception during a country or rustic surroundings. Beadboard is flexible enough that it’s sensible in only regarding any space within the house.
You can find it in 4 ft. by 8 ft. panels within the huge home centers like Home Depot. Usually, the panels run about $20 each, are 3/8″ thick, and are made of pine. This is a soft wood which will expand and contract with changing seasons, so paint the panels before you add the bottom and top rails.
The beads on these panels ar regarding one 1/2″ wide. If you want more width, you’ll have to by tongue and groove boards and assemble them individually. If you go this route, the cost will be greater, and the installation time will be more, but you have much more choice as to the look of the paneling once it’s finished.
I have visited several historic buildings over the years, and the Early American carpenters were pretty imaginative about how they assembled beaded wall panels. I’ve seen three or four widths combine in a repetitive design; alternating 2 widths; and I saw a room where 8″ wide planking was used on one wall and 2 1/2″ wide beadboard was on another wall.
Having imagination about these things is all well and good, but the steady, constant repetition brings a sense of uniformity that I believe is what most people look for. Height is another aspect where you will have a lot of flexibility.
The minimum height ought to be “chair rail height” or 34″ higher than the ground. However, your decorative scheme might be better served if your panels were 40″ high, or 48″, or 60″, or anything in between.
The best thing to do is to make templates or sample pieces out of cardboard or some other inexpensive material. Tape them to the wall and leave them there for one or two of days. Then try it again, using a different height. Decide that you wish best, and go along with it.
Your top and bottom rails should be notched out in the back so that the panels fit inside the rails and the rails touch the walls. This will eliminate gaps between the rails and the walls.