Caulking a bathtub requires skill and patience

November 18, 2011

The caulk around my tub is pretty gross. It’s missing in places where the ceramic tile meets the tub. What’s an easy way to remove old caulk? What kind should I use to re-caulk? What are the biggest mistakes a person makes when re-caulking a tub?

— Lafawnda S., Boise, Idaho

 

Leaks around tubs can often be traced to bad caulk jobs or missing caulk. The trouble is that many people don’t know how to caulk a tub properly. It’s not hard to do, but don’t be fooled by those TV shows and smiling personalities promising that “it’s so easy to do!” There is some skill involved, and you need to know a few things.

Let’s start with removing the old caulk. Using a razor knife, you should try to cut away as much of the hardened caulk as possible. The flat razor scrapers used by painters to remove paint from glass work pretty well for this job. Just take your time and slide the blade between the caulk and the surfaces it touches.

Make repeated light strokes with the razor knife, not one cut stroke using lots of force. If the knife slips, you can quickly damage yourself or something in the room. You want the tool under control at all times.

If the caulk is too hard to cut, it can be softened with liquid caulk removers. These work best if you soak narrow strips of paper towels in the solvent and lay them on the caulk. Then immediately cover the paper towels and caulk with a wide piece of blue painter’s tape so the solvent doesn’t evaporate. The next day, the caulk should be easy to remove.

Once the old caulk is gone, it’s time to clean the tile and tub and dry it. Use small amounts of water and the cleaner of your choice to remove any traces of dirt, soap film, grease and so forth from the tile and the tub. Use white vinegar to remove hard water deposits. All surfaces that are going to receive caulk need to be clean and dry.

The places that need caulk are the joints where the tub and tile meet one another and where the tile abuts faucets, spigots, shower arm pipes, floor tile and so forth. Think about where water splashes and where you might see it outside the tub after you use it.

All these places need to be sealed so that water cannot flow or seep behind walls or under floor tile, or migrate to where it can cause mold and wood rot.

I like to use water-based caulks that are labeled for tub and shower use. There are general-purpose caulks, but they don’t seem to be formulated for the high-moisture environment you have in a home shower and tub area.

The biggest mistake you can make while caulking a tub is failing to have the surfaces clean and dry. Remember, caulk is just glue. It’s sticky. It adheres to things, but if the surface is not clean, it will not bond well.

In some situations, water can get behind the tile and tub and soak the substrate. If this happens, it will be virtually impossible to get the new caulk to dry and cure. The water behind the wall will keep the new caulk in a semi-liquid state and when you use the shower or tub, the caulk will wash out. I’ve seen this happen.

You can use a fan, a hair dryer or some other blower to get the crack between the tub and the tile to dry. If left to dry without these aids, it can take a week or more. This means you’ll need another location to bathe and shower.

Another big mistake is failing to tool the caulk so that it’s feathered out well at the edges. The caulk joint needs to be smooth. Avoid smears on the surfaces. Caulk needs to look professional. That comes with practice. I recommend that you set up two scrap pieces of ceramic tile at a 90-degree angle and practice.

Watch the video I have on my Web site that shows you how to tool caulk. Type “caulking video” into the search engine at www.askthebuilder.com.

Tim Carter is a columnist for Tribune Media Services. He can be contacted through his Web site at www.askthebuilder.com. ©2009 Tribune Media Services

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