If one of the tiles is fairly flat with minimum warping cupping you may meet the proper coverage requirement using a 3 8 square notched trowel.
Proper trowel for wall tile.
This trowel size is good for uncoupling membrane.
Use this for 8 8 s and some of the 5 16 thick 12 12 builder grade tile.
The larger the tile the larger the trowel.
1 4 x 1 4 u notch.
Four inch up to 8 inch tiles need a 1 4 to.
If you do not have proper coverage you need to back trowel the tile or use a larger trowel.
Twelve inch square tiles for instance are best applied using a trowel with 1 2 inch by 1 2 inch notches.
With your 12 24 tiles you should use a 1 2 notched trowel on the wall and back butter each tile but just with a skim coat.
Finding the right trowel for the job is quite simple when you know that generally speaking the trowel size should match up to the tile size the smaller the tile the smaller the trowel.
Basic trowel size as a general rule mosaic tiles up to 2 inches wide benefit the most from trowels with notches that are 1 8 to 1 4 inch in size.
1 8 x 1 8 notch.
1 4 x 1 4 square notch.
The trowel i normally have in my hand is a x x 3 8 square notch i use it for most of my installations and to irritate random pets.
The other main consideration is where the tiles will be set on the floor or on the walls and ceilings.
Tile trowels come in many shapes and sizes generally starting out from a 3 16 v notch up to the 1 2 square notch.
Select a trowel based on tile size mortars.
1 4 x 3 8 square notch.
If however the other tile has quite a bit of cupping you may need to use a larger 1 2 square notched tile trowel to get proper coverage.
This may also be a good trowel size for thicker 5 16 mosaics.
Here is a list of the most common trowel sizes and what they re used for.
Tile trowels come in many shapes and sizes generally starting out from a 3 16 v notch up to the 1 2 square notch.
Mosaic tiles and wall tiles up to about 4 by 4 inches call for a v notch trowel with 3 16 by 1 4 inch notches while larger tiles require a trowel with a square or u shaped notch to obtain proper adhesive coverage.