I have selected large format Porcelanosa wall tiles (33.3 cm x 100 cm) for a bathroom. From the brochures I have seen, these tiles tend to be mounted with a very minimal, almost invisible grout spacing. Our builder has started to mound these using a more regular 3mm spacing, which I am worried will look odd. He said that trying to mount with a 1mm or 2mm spacing will result in the spacers compressing and making an even finish very difficult. Is this true, or is there some special technique needed for large format tiles with a small grout gap?
I think that 33.3 cm x 100 cm (13.1 inch x 39.4 inch) large format tiles will actually look good with a 3 mm (1/8 inch) grout line.
The builder is probably using clips to hold the tiles to the wall, and the ones I've used are thicker than 1 mm. These clips help make the tiles flush with each other as the tile adhesive/thinset dries. If they install them without using clips (or another system) it will be exponentially more difficult to install well.
If you want the grout spacing smaller than 3mm, I would ask the builder what the smallest spacing they can do without extra work with their clip system, and ask them if it's possible to use another clip system that would work better?
If the tile you chose is rectified, then you may use any size groutline you like, it's that simple. If it isn't, then most manufactures will recommend a 3/16 groutline due to tile variation. If he doesn't know to use rigid spacers to handle the weight or to use a mortar made for large format tiles that can support that weight, stop him now.