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.
Type of trowel for wall tile.
Actual coverage depends on substrate type of tile and setting method.
This can either be a.
A 6mm x 6mm trowel will leave a 3mm bed of adhesive beneath the tile.
1 4 x 1 4 square notch.
This trowel size is used for thinner membrane installation and not typically used for tile.
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.
How to choose a tile trowel square and u notch trowels.
A great trowel for installing small ceramic tile such as 4 25 x 4 25 6 6 and 3 6 subway tile is this 1 4 inch square notch trowel.
Twelve inch square tiles for instance are best applied using a trowel with 1 2 inch by 1 2 inch notches.
Tile trowels come in many shapes and sizes generally starting out from a 3 16 v notch up to the 1 2 square notch.
Use this for 8 8 s and some of the 5 16 thick 12 12 builder grade tile.
Also make sure the thin set mortar you hand mix yourself is also rated for vertical surfaces.
1 4 x 3 8 square notch.
This may also be a good trowel size for thicker 5 16 mosaics.
1 4 x 1 4 u 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.
This trowel size is good for uncoupling membrane.
The other main consideration is where the tiles will be set on the floor or on the walls and ceilings.
V notch trowels are the preferred type for walls but they are not mandatory.
1 8 x 1 8 notch.
The v notch is superior.
Tile trowels come in many shapes and sizes generally starting out from a 3 16 v notch up to the 1 2 square notch.
Using a u notched trowel and embedding the tile into the adhesive leaves you with a bed of adhesive beneath the tile a little over 1 3 the size of the trowel teeth.
Here is a list of the most common trowel sizes and what they re used for.
Anytime you use 12 x 12 or smaller vertical wall tile you always use a v notched trowel rated for tile installations since it is made specifically for vertical surfaces to bond the mastic mortar successfully.
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.
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.
The most common type of trowel for floors is the u notched trowel.