If you decide to replace the grout with caulk, be sure that you remove all the existing grout with a grout saw, and then vacuum any remaining grout so you have a clean surface. … Smooth it out before pressing gently down on the caulk to push it deeper into the joint to give it a firmer connection.

Is it bad to caulk over grout?

Caulking over grout will lead to peeling caulk and will likely cause a colony of mold spores to grow between the caulk and grout. To achieve a good-looking, waterproof seal, remove the grout and apply silicone caulk in shower corners.

Can you apply silicone on top of grout?

You can put silicone caulk over cracked grout as a temporary solution, though it’s not generally recommended. Silicone caulk will not hold well over the grout for an extended period of time, as it’s not meant to bond to it.