Grout Joint Width - Is there a standard that lists recommended grout joint sizes for tile?
The ANSI and MIA standards do say grout joints should never be less than 1/16" wide, and depending on the type and size of tile they should be wider. It is recommended to always have at least a 1/8” wide grout joint for floor tiles in order to be able to fill the grout joint full. What dictates what width the grout joint should be is how consistent the tile is in its facial dimensions. Irregular sized tiles need a wider joint to allow for a straight grout joint e.g. Mexican pavers with ¾”+ wide joints. Rectified tiles are very consistent in size so you can get away with a 1/8” wide grout joint. Normally on vitreous and semi-vitreous clay body tiles you can have a 3/16” or ¼” wide joint. Use sanded grout for joints 1/8” wide and larger. Good Luck!