I have a question. I am building a chair wall on a kneewall standing in front of another full sized wall. It will be straped out horozontally, and all insulated, vapor barrior the works. I don’t know why this sticks in my head maybe, there is something to it. Thats why am drawing on the wealth of knowledge here. Is it important to sheet the wall with drywall or plywood, under the T&G edge and ceter board? Is there a reason i can’t remember?  I do remember tearing out a wall and re hanging it because they painted it after it was installed. The boards shrank and all of the tounges made bright lines over time, which really stood out and detracted from the appearence. We tore it out and repainted it all. probably a case where the owner didn’t know what color she wanted. I wonder if I am confusing this question, with that answer. its been a few years. I wanted to see if anyone else had anything to say about it. I don’t see the need really. The finished wall will be a chevron pattern alternating down the length of the wall. probably natural finish. Thanks