There are a few probable causes but before you tear up the tile and start over try this quick cracked grout fix.
Fix floor tile grout.
While grout is a durable material tile surfaces suffer a lot of wear and tear that can crack it resulting in a shabby look.
Measure the space between the tiles.
Choose the correct type of grout based on the width of your tile joints and where the repair is being done.
Dealing with cracked grout is a common issue that comes up for many homeowners at some point.
Once the grout cracks for any reason it s time to repair broken grout before there is any damage to the surrounding tiles.
If the width is 1 8 of an inch or smaller use an unsanded grout.
Is the grout between your floor tiles cracking or worse crumbling away.
Use a grout saw that has a blade with a width that will fit between the tiles you re working on.
2 remove damaged grout and debris with a grout saw.
If the space is larger than 1 8 of an inch use a sanded grout.
Be extra careful with this step as you can scratch or chip tiles during the scraping process.
3 follow the instructions on the grout to create.
A grout saw is a small handheld blade that fits between the gaps in tile.
Remove all the loose and cracked grout with a grout saw or dremel tool and completely vacuum out the gaps.
Grout is available as sanded or unsanded.