Symptoms
- Grout falling out in small chunks or powder
- Visible gaps between tiles with no grout at all
- Grout feels soft or sandy when touched
- Often worse near tub, shower, or sink edges
Likely causes
- CommonAge and normal wear of the grout materialGrout has a lifespan and eventually becomes brittle and crumbles.
- CommonWater intrusion breaking down the grout from moisture exposureWet areas like bathrooms and kitchens see faster grout deterioration.
- PossiblePoor original grout mix or applicationToo much water in the original mix weakens the cured grout.
- PossibleMovement in the substrate stressing and loosening the groutFlex in the floor beneath can shake loose grout that's already brittle.
What to do
- Use a grout saw or oscillating tool to remove all the crumbling and loose grout down to the tile edge.
- Vacuum thoroughly to clear dust and loose particles from the joints.
- Check the tile edges themselves for chipping while the joint is exposed.
- Mix new grout matching the type and color of the surrounding grout.
- Apply with a rubber float, pressing firmly into the joints at a diagonal to avoid pulling grout back out.
- Wipe excess with a damp sponge before it sets, then let it cure fully per the product instructions.
- Seal the new grout once cured to extend its life and resist future crumbling from moisture.
Tools and parts
- Grout saw
- Rubber grout float
- Sponge
Matching tile groutSearch: “matching tile grout sanded unsanded”
Grout sealerSearch: “penetrating grout sealer”
When to call a pro
Call a tile professional if crumbling grout is widespread across the floor or near a shower/tub, since water intrusion there can affect the subfloor.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.