To Caulk or Not to Caulk?

House Doctor | Gary Dymski

January 22, 2004

Q. We had a new second-floor bathroom installed, including wall-to-ceiling tile, a new tub and toilet. The tile installer told us to caulk around the tub. I always hated caulking around the tub. It never looked good. Mildew always seemed to grow and the caulk often needed replacing. I happened to mention this to the plumber and another tile installer who were working at a friend's house. They both said they do not caulk around tubs, where the top meets the tile. They just said to make sure the grout line was in one piece. What should I do? -- Caroline La Scala, Oakdale

A. Personally, I think the guys who told you not to caulk are crazy. Grout is cement and sand and color. When hard, it has very little elasticity. When your tub is filled with water and a bather, it moves ever so slightly. This movement, as well as temperature and humidity changes, lead to the grout line separating and the growth of mildew.

Here's what I do: I make sure to use a grout with a latex additive (for elasticity) and then I always use a silicone caulk around the tub. Depending on how often the tub is used, I might have to clean and replace the caulk line two or three times a year. To get rid of any mildew that develops, spray the area with a 50-50 mix of chlorine bleach and water and let it set. The mildew will be gone the next time you shower or bathe. To remove old caulk, use Caulk-Be-Gone by DAP (about $5 a tube). The gel softens the old caulk in as little as two hours so it can be scraped away with a plastic putty knife. You also can use a single-edge razor blade to scrape remaining caulk off the tub or tile. When it's clean, rinse with water. I also use a hair dryer to blow the gap free of debris and dry the area. When it's dry, lay a new bead of caulk.

Here's a tip: Create a seam for the new bead with masking tape. Run a strip of tape along the bottom row of tile, about 1/16 inch above the tub edge. Run another strip on the tub, about 1/16 inch from the tile. You'll be left with an exposed area, about 1/8 inch wide. Carefully run the new bead of caulk into the exposed area, then set the bead with a wet finger. Let the bead set for a few minutes, then remove both strips of tape.