Why epoxy?
Cement grout is yesterday.
Standard cement grout absorbs water, stains from coffee and food, cracks along tile edges, and needs re-sealing every year. Even then, it goes grey within 3–5 years.
Epoxy grout is a two-part compound (resin + hardener) that cures into something more like a plastic than a cement. It's fully waterproof, immune to stains, never cracks, and never needs sealing.
It costs about 2× cement grout up front. But you'll never re-grout again — and it looks exactly the same as the day it went in, 15 years later.
