Nooo I thought we were finally moving past the horrible faux shiplap phase. Skip the shiplap and skip the accent wall. Feature walls only work if you're highlighting something that's interesting.

Where does this shiplap desire come from? I've noticed that people that have no other decorating knowledge always want an accent wall.

Sina, "Only" ? I'm sure there are exceptions.

The OP didn't ask what you all thought of shiplap, she asked what size to do.

Andrea, I would take into account how large the space is and how tall your ceilings are.

Also, if you are ripping them yourself from a piece of plywood, cutting them at 5 7/8" will give you eight, equal 8' boards w/no waste.

if doing pre-cut pieces, I like a 6", but it depends on the look you want.

This poster had the same question, you can read through here for other answers

https://www.houzz.com/discussions/what-size-shiplap-should-i-use-for-my-kitchen-dsvw-vd~2691573

IMO it is the responsibility of pros on this site to offer more than just the answer but also some opinion. Most posters have no idea what shiplap even is so maybe help with that first

Seems like the same "old" posters that cannot stand shiplap keep posting their negativity. Like they did on this thread:

https://www.gardenweb.com/discussions/5053315/shiplap-and-trim-same-color-white#23132433

I still stand by my opinion of shiplap. Unlike a paint accent wall, shiplap will be harder to remove later on, another reason I don't recommend it. And while feature walls don't "only" have to accent a pre-existing interesting feature they tend to work best when they do. Also, love everyone that criticised me for not answering the question and then failed to answer it themselves.

Shiplap is a material that was commonly used as an exterior siding for barns and homes in the South (mainly Texas). REAL shiplap is expensive. Most of what is used today is just regular wood boards painted white.

If you're set on the shiplap, I'd say go 6 inch but it depends on the ceiling height. Do a little math to see how many boards you can fit on the wall with each size and where you'd have to have cut pieces.

Sina,,,I did answer her. why don't you read my first comment?

Wasn't referring to you Beth!

I think Patricia was agreeing with you. she and I were the only ones that mentioned "answering OP's question". not a big deal. can you imagine if everyone decorated in the exact, same manner? to me, it's boring. I think people like what they like and ought to do what they like in their home. So what if 10 years down the road it's a little difficult to remove. remember 1950's paneling??? how was that better?

Measure from ceiling to floor accounting for gap and board size and see how the boards will wind up on the wall. You don't want to get stuck with a 1" strip on top if avoidable.

The baseboard goes on last anyway so you can use the height to help adjust the board heights. You can also rip the tongue off and use it as a baseboard. It finishes the smile a little better and you then terminate you adjacent walls use into it.

Shiplap like any product looks good or bad depending on how its used. A general blanket statement of it being in or out is useless.