How much should Grout Joint Widths vary in size in a Tile Installation?

QUESTION

Hello, My contractor installed 2' x 2' porcelain rectified tile to my kitchen. I wanted 1/16" grout lines but was told that the recommended lines should be 1/8" so I agreed to that. The area is 350 sf. The installer use spacers. The tile is now installed and a few of the tile are actually 1/8", most are larger than that and about 20% of the floor grout lines actually measure 1/4". My question is, is it reasonable for the grout lines to vary to that degree.

ANSWER

ANSWER - The tile industry standards say that grout joints should never be less than 1/16" wide, and tiles should never be butted up to each other.  It is recommended that the grout joints be a minimum of 1/8" or wider depending on the sizing tolerance of the tile being installed.

What dictates what the grout joint width should be depends on how consistent is the tile sizing or how much variation there is in sizing.  The standards state that the grout joint width shall be at least three times the actual variation of facial dimensions of the tile supplied.  The standards for calibrated porcelain tiles allow for about 1/16" size variation, so the grout joint width should be at least 3/16".   Rectified porcelain tiles allow for about 1/32" size variation, so the grout joint width should be at least 3/32".

The standards state that the nominal centerline of all grout joints shall be straight with due allowances for hand-molded or rustic tiles.  There is some language being considered to add to the ANSI standards that say that the grout joint widths shall not vary more than +/- 25% of the intended grout joint width; other than for hand-molded or rustic tiles.

So if the intent was to have a 3/16" wide grout joint, then plus or minus 1/16" (1/8" to 1/4") could be reasonable depending on the type tile that was being installed.

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