Grout or Caulk (or Both) in the Shower?
Tile expert Mark Ferrante knows why that shower grout is getting moldy
For the fourth year in a row, I’ve removed cracked, moldy grout from the perimeter of my shower floor where it meets the tiled wall. Should I caulk that seam this time, or grout, then caulk?
—Elizabeth Beck, Land O’ Lakes, FL
Stay away from caulks or sealants in that location; they can’t be trusted to keep out water in the long run. But you can count on them to grow mildew, sooner or later.
The best solution would be to fill that joint with epoxy grout, such as SpectraLock Pro Grout. It looks like a regular sanded grout, but it’s waterproof, adheres tenaciously, won’t crack or shrink, and doesn’t stain or need to be sealed.
Before you start, make sure the joint is clean and completely dry; epoxy can’t stick to wet surfaces. To minimize cleanup, apply masking tape along both sides of the joint. And protect your skin with nitrile gloves; epoxy causes dermatitis.
After thoroughly mixing the two liquid epoxy components and adding the colored powder, pack it into the joint with a margin trowel, then smooth it with a Popsicle stick or other round-end stick. Now remove the tape, smooth the joint with your gloved finger, and walk away for 20 to 30 minutes. When you return, gently clean up any residue with a damp sponge.
You have 48 hours to wipe away any remaining epoxy residue, using a clean rag dampened with white vinegar, but keep the vinegar off the regular grout. The shower will be ready to use after two days.