Grout Joint Width Guide

Why do we need grout joints?

Grout joints serve two critical functions: they accommodate slight variations in the size of the tiles, and they absorb stress from the expansion and contraction of the subfloor. A completely "seamless" tile floor with tiles touching each other will inevitably crack or tent (pop off the floor).

Rectified vs. Non-Rectified Tile

The width of your joint depends heavily on how the tile's edges were manufactured:

• Rectified Tile: These tiles are cut or ground after firing to ensure exact, perfectly straight edges. Because they are uniform in size, they can support very narrow grout joints (typically 1/16" or 1/8").
• Non-Rectified Tile: These tiles are molded and fired, and shrink slightly during the firing process. They have slight size variations. They require larger grout joints (3/16" or 1/4") to visually hide these variations.

Standard Recommendations

• 1/16 inch: The narrowest recommended joint. Only suitable for high-quality rectified porcelain, natural stone, or precision glass.
• 1/8 inch: The standard for most modern floor and wall installations using rectified tile.
• 3/16 to 1/4 inch: Required for non-rectified tiles, subway tiles with built-in spacer lugs, or large format tiles on a floor that isn't perfectly flat.
• 3/8 to 1/2 inch: Used for irregular materials like Saltillo (Mexican terracotta), quarry tile, or rustic cobblestone looks.

The "Lippage" Factor

If you are laying large rectangular tiles (like 6"x24" wood-look planks) in an offset pattern, the center of the tile is often slightly bowed upward. If you put a narrow 1/16" joint, you will feel the edge of the tile with your bare feet (lippage). For large offset tiles, the TCNA recommends a minimum 1/8" joint (often 3/16") to smooth the transition between the bowed center and the flat edge.