That type of tile requires larger spacing or you will have lippage. The wall looks to still need more prep to make it flat, or the use of T or X spacers will show the waviness of the wall underneath in some serious lippage telegraphing through.

All tile should be applied with thinset, including any edging pieces. A good quality white thinset like Mapei Ultralite is what you need here. No mastic in a bucket.

Sand is an important part of grout, as it is what gives it body and strength, plus prevents sagging. If you want a light colored grout that blends, look at Mapei Ultracolor Plus FA in Frost or Warm Gray. It has an ultrafine aggregate that can bridge between the recommended sizes for sanded and unsanded grout widths.

Does the manufacturer allow 50/50 joints? The 4x12 I used was limited to thirds. I've had good success with mastic in a bucket for a backsplash.

Yes, we are going with traditional and not thirds. we are using thinset over mastic. We have an area behind our sink and live by the ocean/water…high humidity. Although the mastic looked less messy to me, I wanted thinset for possible moisture concerns.

I am considering using something other than thinset to attach the edging bc so thin (and want a clean edge/quick set).

If you are doing a 50/50, you will need a minimum of 3/8 spacing, and more advance wall prep. Otherwise you are setting yourself up for major lippage issues. That gets highlighted any time you turn on your under cabinet lights.

If you do not have under cabinet lights planned, stop now, and have that wiring done before you tile over that space. Under cabinet lighting is the single best upgrade that you can do for any kitchen!

Mastic is fine to use for a backsplash, although I find it to be messier than thinset mortar. I would do 1/8" joints. 3/8" is much too large and will make it look like a sea of grout with tile added to it.

You need a grout joint between the field tile and the liner tile. Use the same size grout joint used in the field. Use the same thinset mortar to set the liner. You can use some blue tape to keep it from shifting until it sets.

You didn't answer the question if the manufacturer accepts 50% offset, or if they recommend nothing greater than 33%. I recommend you do a sample board to confirm that you like the grout spacing and the offset. You should have a sample board anyway to try out the grout color.

Thanks all for advice. I had some specific questions which it looks like I was not clear on. I’ll have to edit post or delete :).

Yes, tile is ok at 50. We used thinset. There is no lipage. Most is up. Working on one side that will have the liner (which was pictured). wanted to know if I needed to allow 1/16 for liner (which I think I do). Second, wondering if I could use other medium for liner only since so thin. i have read where others use an adhesive for delicate pieces.

@catbuilder thanks in regards to spacing on liner/adhesion.

"All tile should be applied with thinset..."

Not if you'd like to save time which is money.Grout in anhour.

I think it'll look tidier if the spacing to the liner is the same as between the tiles.