Is it possible to grout over grout? I thought that was a sure way for failure?
It is if you are applying regular grout over grout. Grout is not a adhesive so it will not stick to anything. It is designed to wrap around the tile and also needs to be the full depth of tile. This locks the grout and is more of a mechanical bond.
So what can I use?
Epoxy grout is part epoxy and part grout. The epoxy will bond to just about any CLEAN surface. I like to remove the top layer of grout with a utility knife or an oscillating tool with carbide or diamond blade.
Once the surface is clean and dry, you can apply the epoxy with a small 1-2 oz syringe, smooth with finger or wood stick with round corner like a popsicle stick or grout float, scrub with white nylon pad using warm water, then wipe residue off tile with a clean microfiber cloth and keep dry for 24 hours.
I like to use Super Grout Additive available at www.ceramictilepro.com. visit the youtube channel for more info.
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Shower Pros of Roseville Folsom Sacramento
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Epoxy grout was applied over existing grout AFTER area was cleaned thoroughly. I always use Super Grout Additive.
Using a simple rubber caulk application tool, epoxy was smoothed into grout joints with ease and very little waste. The tool used here is Caulk tool.
Shower Pros have over 30 years experience with all aspects of tile and grout. Call for a free estimate 916.600.2009