That s assuming the tiles are indeed perfect in size.
Marble tile grout size.
You never want tiles in direct contact with one another.
This thickness leaves room for the natural variation in size and the perfectly imperfect edges of handmade tile.
Finished grout lines will vary from 1 16 to 3 16.
Literally zero variation in size and all perfectly rectangular.
Marble flooring installed in different sized repeating patterns such as the versailles pattern require large grout line widths.
Large grout joints will require the use of sanded grout.
For the size of the tiles you are using the minimum grout line width for the 12 wall tile is generally 1 16 and for the 24 floor tile 1 8.
Note that using the smallest grout possible will increase installation time.
Actual finished grout spaces will vary from 1 8 to 1 4 if 3 16 spacers are used.
If smaller spacers like 1 8 are used it will accentuate the size difference of handmade tile.
You can space marble tiles on a fireplace as wide as 1 8 inch apart or as narrow as 1 32 inch.
Tiles that vary in size and shape need large grout joint widths 3 8 to 1 2 inch.
Fill grout joints on natural marble with joints larger than 1 8 inch with sanded grout.
All other cuts of tile from tumbled to chiseled to punched contain slight variations in shape and size.
Generally sanded and unsanded grout should never be mixed and absolutely never with marble or any other surface that can be scratched by the sand in grout note.
This will create a smooth slab like surface out of the flat tops of the marble tile.
Joints wider than 1 8 inch can result in cracked grout and joints narrower than 1 32 inch might.
Rectified tiles are perfectly uniform with precisely defined edges requiring the least amount of grout.
A higher quality tile could allow for a 1 16 or 1 8 grout line and maybe even a brick layout as lippage may not be an issue in a perfect tile world where as a lower quality tile might have major lippage risk so laying the tile in 1 3 s and having a 1 4 grout line is recommended.
Grout lines can vary greatly from jointless installations showing no or virtually no grout to about 1 4 inch.
First the smallest grout lines less than 1 8 inch are ideal for rectified tiles.
Marble is a cut product manufactured to extremely tight tolerances and usually designed to be installed with 1 16 spacing.