Cracked floor grout often starts with movement
Cracked or loose grout has several causes, and the Tile Council says a field inspection is often required before anyone names one. The FAQ's usual list starts with too much deflection in the substrate. That movement cracks grout and, if it is severe, cracks tile as well.
Packing and mixing
Wall joints are easy to bridge if the grout is not forced to the back of the joint. Sanded grout in a joint narrower than 1/8 inch can sit on the surface because the sand grains do not pass through. Too much water or polymer leaves a weak structure after the extra liquid leaves. Adding water after cement hydration has started in the bucket makes grout that packs but crumbles later.
What an inspector looks at
Joist spacing, joist size, span, plywood direction, gaps between sheets, adhesive type, and coverage all belong in the check. The FAQ's usual minimum sketch is 16-inch on-center joists of 2x10 or better for the span, with 3/4-inch subfloor plus 1/2-inch underlayment, or a backer board made for tile. Defective grout is the least likely item on the list.
Source
Fetched 2026-10-11 from Tile Council cracked and loose grout FAQ. The sentences above follow that page. They are not a contractor promise.
Related notes
- Tile notes index
- A hollow sound is not always a loose floor tile
- Porcelain means 0.5 percent water absorption or less
- Backsplash photos
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