Marble is porous and could easily absorb color from the grout, so it’s important to seal the stone before you grout — even if you’re using white grout.

What happens if you don't seal marble before grouting?

While not all marbles are delicate, most are highly absorbent, and thus easy to stain and etch. Polished marble shouldn’t need sealing before you apply grout, but tumbled marble does — it’s so absorbent that the grout itself will stain it during the installation process unless you seal it first.

What happens if you don't seal marble tile?

If you don’t seal your marble floors, any bit of moisture leaking through could cause marble to lose its shiny, glossy look.