1. OVER proper waterproofing. Neither cement board or tile is waterproof.

2. NOT in a brick pattern. 33% offset is the max offset. With 50/50, you are assured lippage.

3. Using LHT mortar, not thinset. You need something stickier and more able to handle the size and weight.

4. 3/16 spacers as the starting point for spacing. The more warped the tiles are, the bigger the grout line needs to be.

5. Creating roughly equal cut size at corners that wrap around the corners. Each wall is not handled independently. It's done as a whole.

You need a real tile contractor. This is out of your lane. https://www.ceramictilefoundation.org/find-certified-tile-installers

I am hiring someone and I will be using cement board with RedGard.

Is there less of a concern with lippage with Italian porcelain tile?

I didn't know that I needed to set these tiles with mortar. Thinset was mentioned.

Thinset is a type of mortar. So is Large Heavy Tile mortar. ProLite is a good option, easily available. Be wary of red guard contractors. They often detail the jobs incorrectly. A foam board or applied membrane contractor generally is a step up in skill.

This shower is the is 72" but using 12 X 24 tiles. Hard to see but of you enlarge it you can see the basic layout they've used.

Cook's Kitchen, what do you mean by incorrectly?

Be wary of red guard contractors. They often detail the jobs incorrectly.

I'd prefer we don't get into a side discussion about lippage. I understand the concept.

Either jack on jack (checkerboard) or running bond (brick pattern) the first tile should be centered and the whatever needs to be trimmed out of the last tiles should be equal. so 6' tile pieces on the ends sounds about right.

However if you treated all the walls as a whole pattern you could start at one 36" end and cut the last tile in half then use that other half to start the 60" wall. This would give you less tile cuts and a continous pattern. Plus less grout lines means less chance for unevenness called Lippage and less grout to grow mold.

I have to laugh with the "red guard contractors". Yeah using membranes and mixing and matching different name brands and components to do a simple shower is the way to go. The more components you add the more to fail. Schluter saved everyone with their barrage of internet advertising.

Heavy tile require a strong base. Your best bet would be simple roofing felt and some floated walls. This entire waterproofing deal is just out of control on here.

One more time, the entire issue was when green board was being sold as or though to be waterproof. Tiling was done right over the gypsum board and when water intrusion happened the board crumbled and mold formed. Funny thing is do you know how many showers are still being used exactly like that with zero issue? There isn't a tile person incl myself who did not do showers like that back then. I had one in my own home that was going on 20 plus years without an issue as the caulk and grout was always kept up.

Do most people even realize these membranes and some roll on waterproofing are still designed to be used on gypsum board. thats their entire purpose not for cement board although of course they can be used on them.

Pick a tile that works for your layout. What you are seeing is what happen when these offshore Co's produce tile not taking into account normal US shower or tub sizing. Heck, they can be floor tiles?

It's not uncommon for large format tile to be warped and have lippage. If you want to avoid this, be particular about the tile you buy: get samples and place them face-to-face to see if there are any gaps...in the middle or at the ends. I have 12 X 24 tiles on my shower walls and I checked quite a few of them this way before installation to insure they would be dead flat. Even then, I still had them installed in a stacked pattern, rather than a running bond to reduce any chance of lippage.

Lippage is a non-issue when using T-Lock or similar tile leveling system. It costs extra no doubt however a must for 12x24 or larger format tiles. Our tilers used 1/16" T-Lock for entire home, floor and walls, including bathroom floors and shower walls, an incredible job indeed.

A good tiler does his calculations for each size/direction/layout of floors and walls they cover before laying the first tile. We used straight horizontal tile layout for our 120"x48" master shower walls and master bathroom floor whilst we used 50/50 horizontal layout for all guest bathroom 72"x36" shower walls and floors.

I think with so many conflicting opinions I'd rather just go with the TCNA recommendations. I think that means a third offset.

Buy a TCNA manual and learn about why topically applied liquid coatings are the riskiest route. It’s typically used by the same type of contractor who does a vinyl liner flat to the floor and who just staples it to a wood curb and screws on cement board over it and then pours a slope. He uses it because someone told him he had to, and not because he understands anything about how shower waterproofing works. https://www.tcnatile.com/products-and-services/publications/218-english-publications/188-handbook.html

A single system, done correctly, carries a warranty. A single system, done incorrectly, will not, but the manufacturer generally helps out anyway. Any system is only as weak as the most incorrectly done part of that system. The weak point is always the contractor.

A hacked system of half of one and a dozen of the other never has a warranty to start with, even if the contractor “assures” you that he has done it that way “for 30 years”. Those are the contractors to avoid at all costs. If they aren’t taking industry education classses, and changing and improving their work every year, do not hire them! You will regret it.

https://www.ceramictilefoundation.org/homeowners-guide-to-hiring-qualified-tile-installer 

Here’s a failed job being torn out. See the red?

We have a Kohler shower pan installed already so it's just the walls.

These redguard jobs rarely [almost never] fail because of the walls, they fail because of the floor is not done correctly, because floor membrane is not properly applied. Because contractors leave nails or screws that stick out. And Your pictures prove the point.