I have a bathroom wall that I'm wanting to re-grout. I've removed the old grout, and have found there's a space between the back of the tiles and the wall. The tiles seem pretty solid though (after pushing on them, they don't seem to be going anywhere).

The problem is when grouting the vertical gaps in the tiles, the grout just falls through and into the space between the tile and walls. I'm not sure how the original tiler/builder managed to grout this.

I was thinking of packing the gaps with material (foam I guess?) so the grout has something to sit on. Does that seem right? Or are there an other ideas out there?

  • Grout bag and pump the joints full of grout?
    – redlude97
    May 8, 2021 at 10:20
  • I think that would encounter the same issue - the grout just falls through the joint and into the space between the tiles and wall. I mean, eventually it would work once I pump enough grout to fill the entire space...but that would be a LOT of grout, lol.
    – sjl
    May 8, 2021 at 10:29
  • If it is not a pre-mixed grout, you shall add a minimum amount of water to make a stiff mix, which is more stable if applied by hand at a slow rate. Then smooth the surface using a wet towel. Don't forget to wear gloves.
    – r13
    May 8, 2021 at 16:17
  • I'd rather fill the voids with grout since hollow tiles are inherently unstable. Foam isn't stable either and the grout will crack through eventually
    – redlude97
    May 8, 2021 at 21:35

1 Answer 1


I've had great results by packing string/twine into the cracks. It stays in place and gives the grout something to stick to.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.