Tiling

Grout Cracks at Corners Because It's Rigid on Purpose — Caulk Isn't

Grouting a tub-to-tile corner instead of caulking it guarantees a crack within a season or two, no matter how carefully it's applied.

Grout is a rigid cementitious (or rigid epoxy) filler designed to lock flat, stable tile joints in place. Corners, and any joint where two different materials meet — tile to tub, tile to countertop, floor to wall — flex slightly with temperature changes, structural settling, and daily use. Rigid grout has no give, so it cracks at exactly the points where movement concentrates.

Sanded or unsanded caulk, formulated to match grout color, stays flexible indefinitely and is the correct material for every inside corner and dissimilar-material transition. The rule tile setters use: flat field joints get grout, movement joints get caulk.

Put this into practice

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More facts like this

Grout Joint Width Changes How Many Tiles You NeedTile quantity is calculated on tile size plus joint, not tile size — a detail that quietly changes the order on any large floor.
Large Tiles Need a Flatter Floor Than Small OnesA large-format tile cannot flex over a hump. Anything over 400 mm needs the substrate flat to about 3 mm over 3 m, or the edges stand proud.
Grout Sealer Wears Off Long Before It Looks Like It HasShower grout sealed once at installation and never again is typically unprotected within a year, well before it shows visible staining.