Subway Tile Joint Width and Grout

Grout is a design decision disguised as a technical one.

2 mm

Modern, tight, architectural. Demands a flat substrate and accurately rectified tiles. On a handmade-look tile with a slightly irregular edge, a 2 mm joint can look like a mistake rather than a choice.

3 mm

The safe middle. Reads clean without exposing tiny dimensional variation, and suits most 75 × 300 mm porcelain.

5 mm

Period, cottage, industrial. The joint becomes a visible grid, so the grout colour matters as much as the tile.

Grout colour

• Match the tile — the wall reads as one surface, joints disappear
• Contrast — the grid becomes the pattern; good on plain tiles, busy on reactive glazes
• Mid-grey — hides variation and dirt better than white in wet areas

Which grout

Cementitious grout is standard for wall tile. Epoxy is worth the cost in showers and commercial kitchens where cleaning cycles are aggressive. Confirm with the applicator before ordering, because the joint width has to suit the grout, not the other way round.

Talking about tile grout joint width for subway tile is really talking about the pattern: the joint is the pattern.