Cracked grout is a symptom
Grout does not crack because it got old. It cracks because something under it moved, and grout has no flex at all.
So the first thing we do is work out what moved. Regrouting without answering that question is the most common tile repair there is, and it fails, usually within a year, in exactly the same lines.
The usual causes
Deflection. The floor flexes when you walk on it. Common in older houses where the joists were never sized to carry tile. You can often feel it: stand on the cracked area and have someone walk past, and you will notice give. This one needs structural work underneath, not more grout.
No uncoupling membrane. Concrete and tile expand at different rates, and without a membrane between them the slab drags the tile as it moves. Cracks tend to run in long straight lines, often tracking a crack in the slab below.
No movement joints. Large tile floors need soft joints, usually at the perimeter and every twenty to twenty five feet. Tiled hard to the wall on all four sides with grout in every joint, a floor has nowhere to expand and it will relieve the stress somewhere, usually as a line of cracked grout or tented tile.
A genuinely local failure. Sometimes it is just one dropped-something impact, or a small area that never got full mortar coverage. This is the good case and it is a straightforward fix.
How we tell them apart
We tap the floor. Hollow tiles sound obviously different from bonded ones, and mapping where the hollow spots are tells us whether we are dealing with one bad patch or a whole floor that was set with poor coverage.
We look at how the cracks run. Long straight lines that ignore tile edges point at the slab. Cracks that follow a joist bay point at deflection. Cracks confined to one area point at impact or a coverage void.
Then we tell you what it will take. Sometimes that is a half day repair. Sometimes the floor needs to come up, and you should hear that before you spend money on a repair that cannot hold.
What we repair
Cracked and missing grout, loose and hollow tiles, replacing individual broken tiles where you have attic stock or where we can source a match, failed caulk at tub and shower joints, and regrouting where the substrate is sound.
We also colour seal and deep clean grout that is structurally fine but stained. That is a cosmetic job, not a repair, and it is far cheaper than replacement when the floor is otherwise good.
A note on matching: if you do not have leftover tile, an exact match on a discontinued product is often not possible. We will show you how close we can get before you commit.
Where we work
Tile and grout repair from Logan to Nephi, including Murray, Sandy, Midvale, Cottonwood Heights, Holladay, Millcreek, Taylorsville, West Jordan, South Jordan, Riverton, Draper, Lehi, American Fork, Bountiful, and Layton.