I suspect the designer means vertical stack, no offset.

She actually suggested 1/3 offset, vertical placement.

Well if that's the look you both want then I agree with the 1/3rd as with 1/2 you may run into lippage problems due to tile warpage.

Not sure of the pros and cons of either. Is there more than one way to do a 1/3 offset? I thought I read that here on Houzz.

Designer's input is perfect- 1/3, vertical.

The tile manufacture probably specifies max of 1/3 offset as a lot of large tiles do have that written in their specs. We have 12 x 24 porcelain tiles and my contractor used 1/3 offset and a lippage control system (sometimes called levelers) to make sure there wasn't any lippage. It worked great, nice flat installation.

ajcn, they intend to use the levelers also. Does the 1/3 offset give a stair step appearance?

Good catch! It can give a stair step appearance if you do it wrong. Stagger it a different way and it doesn't. I have a pic of this; let me search.

AJCN will look forward to more information on this.

Read the instructions! The manufacturer will tell you exactly what to do. Do that.

Laying the tile vertical can make the room look taller while going horizontal can make it look wider (similar to the vertical vs horizontal stripes on clothes). I think it also gives a more modern feel. We went vertical with the 12 x 24" tile in our shower. Our house tends toward mid-century modern so the modern feel goes with the bones of the house.

Part of the reason that we chose vertical is the tiled bench in the shower. By going vertical with the tiles, there are only vertical grout lines on the bench since the 24" direction of a tile is longer than the the height of the bench and longer than the depth of the bench. If we had used the horizontal direction, there would have been horizontal and vertical grout lines on the bench side and top as well as vertical ones.

There are two ways to do a 1/3 stagger.

In one, you move the tile edge 1/3 of a tile in the same direction for each row so you have 3 kinds of row. E.g. if you move to the left each time and start the first row with a full tile, the next row with 2/3 of a tile and the row after with 1/3 of a tile, then the next row you are back to a full tile.

The other way is to use only 2 kinds of row so the rows alternate by moving over by 1/3 of a tile and then back the other direction by 1/3 of a tile. E.g. if the first row started with a full tile, the next row started with 2/3 of a tile and the row started with a full tile.

I guess one could see the grout lines in the first way as looking like steps of a stair. Personally, I prefer the look with 3 rows of the pattern over the look with two rows. I don't see why one is "wrong" and the other "right". Seems like personal preference in which pattern is preferred.

As far as installation goes: When asked, I just told my tile pro that I didn't like the stair-step effect, and he knew what to do, so if you have a competent tile pro, he or she will know how to handle it. If they are unsure or confused, that's a red flag.

As far as style decisions go: A note about vertical layout. Make sure that you are really attracted to that look (you are going to be looking at it for a long time). It's great that your designer is making recommendations, but it's more important that you like that look. Personally I don't like vertical layouts, they don't evoke soothing feelings of calm for me. Maybe that's because in nature, the soothing, calm things seems to be more horizontal, like the surface of the ocean or a lake; the broad reaches of a tree's branches; the wide expanse of an eagle's outstretched wings; but that's just me. Maybe there are vertical soothing images like waterfalls or sunbeams, that evoke a lovely feeling for people, but I just don't feel comfortable in a space that has vertical tile. It's a very personal thing.

As far as re-sale considerations go, if that's a possibility: Vertical is a very specific choice that could be trendy/modern or not fit in with a traditional house. Anytime you put something very specific in your house, you are running the risk that it will alienate a future buyer. But that totally does not matter if you are planning to stay a long time, so you can just disregard this comment if that's the case.

As far as changing to horizontal: If you change to a horizontal layout though, you still want to do the 1/3 off-set without the stair-step effect, and you can do that like the picture above.

Mine are horizontal with a 1/2 offset and there’s no lippage on either the floor or shower. My tile guy placed them out and checked them prior to installing them. I also had the same layout in my previous bathroom.

Gerry, I think you got lucky.
My nephew sets tile. Doing 1/2 offset on 24 inch tile is something he refuses to do. Except for his other aunt. Because he was matching preexisting work . Took him three times as long as 1/3 offset.

I checked our tile before deciding. Our wall and floor tile are both porcelain but are from different manufacturers. In both cases, there would have been too much lippage with a 50% overlap. That's why we went with 1/3.