Do you need to seal tile floors?

Yes. If it is a ceramic or porcelain tile you only need to seal the grout. If you have a natural stone or quarry you need to seal the tile and the grout. Generally when you install natural stone, you seal the tile before you grout. Otherwise the colorant in the grout will seep into the tile. If the floor is existing you would seal it all at once. Don't forget to use a stripper to remove any old sealer. Make sure the stripper is acceptable for the type of flooring you are sealing. Stone can be very delicate and damage easily. Vinegar can etch marble, granite, and travertine. One last note, you get what you pay for with sealer. Invest in a good sealer and you will get much better, much longer results.