Q:

How to repair the grout on the floor

Should I replace the damaged floor or just the grout?
What kind of grout do you suggest and how to proceed?
Thank you.

A:

The right way: pull up the tiles, fix the underlying problem (flexing floor maybe?), reinstall. This will take more time/money but will fix the issue better, longer.
The cheap way: Fill the gaps with tile epoxy. You clean the damaged area, mix the resin, add color to match the tile, and fill in the crack. Depending on your skill, it may be obvious up close, will probably last 6 months - 2 years, and possibly will look worse over time. but it's cheaper and a lot less time.

