Grout coating on terrazzo floors
Grout coating is a largely misunderstood aspect of terrazzo flooring installation and restoration. When terrazzo floors are installed, once they are found, they are grout coated. When you grind a freshly installed terrazzo floor you get some degree of pitting and rock loss. The mixing causes bubbles in the mix which rise through the mix as the terrazzo cures.
The grinding process agitates the rock and pulls some rocks out. Others can end up with small pits on the line between the rocks and the binder, or solution the rocks are mixed in. All new installations should be grout coated after grinding. When a floor is restored some of the old grout is lost.
Grinders also take floors down to expose new pitting from voids in the floor matrix. The best way to hide them is to hone and coat the floor. Unfortunately those are not the best looking, longest lasting shine floors. When a floor is diamond polished to a high shine then grouted as needed some pitting will still show, but overall the floor looks much better.
A diamond polished floor is the least slippery floor. The reflections are true and resemble polished granite much more than a coated floor and you may have to redo your finished floor seven times before you have to do a polish up on a diamond polished floor. Our diamond polished terrazzo floors last 10 years, on average, before they need a polish up. That procedure normally costs half what a full restoration costs. Hopefully this information can help clear some misunderstandings about grout coating terrazzo floors. Thanks.