Monday, May 14, 2007

How to caulk a tub / shower

This is the page where I maintain a periodically updated version of my Secrets of Tub Caulking post. The updated version is straightforward, skipping over the long story of how I became so frustrated with lousy caulk products and the "assume-nothing-ever-goes-wrong" school of instructions that I created and tested my own "how-to." (If you need a good laugh, and are amused by mildew, crumbling grout, and someone trying to answer the phone using their wrists, you should read the original story.)

The Secrets of Tub Caulking - 2007 Update (plus 2011, 2014, 2016 revisions)

What you need:

  • A four-day period during which people in your household can use a different shower. (The clock starts when you use the cleaning product on the mildew; you can apply grout and caulk 12 - 24 hours later, and then it needs 72 hours to dry.)
  • A plastic scraper with a hooked side for peeling off the old caulk — also, either a metal dental pick or a metal shish kebab skewer will work if the plastic scraper doesn't.
  • A little razor blade with a handle (the type you use to get excess dried paint off windows).
  • A preparation product called the Good Stuff Tile and Grout Cleaner Restorer. Available from your better tile stores. NOTE: This is no longer true; The Good Stuff has been banned by the state of California and even stores outside California have stopped carrying it. Instead use the following three cleaning products, in that order:
  • Dawn dishwashing liquid
  • White vinegar
  • Oxiclean (not chlorine) bleach or bleach spray. You'll find it in the laundry products section at the store.
  • A medium (neither too soft nor too stiff) scrub brush for applying Dawn and using it to scrub the tile and grout.
  • Rubber gloves and old clothes to protect yourself while you work with the cleaners.
  • Painter's masking tape (blue is good) in both wide and narrow versions. Plenty of it.
  • Siliconized acryllic latex caulk, in off-white or another shade that coordinates with the existing tile grout in your tub / shower. One tube should be more than sufficient to go around the tub. A good brand is Color Caulk Premium Tile and Fixture Caulk, and a nice off-white is #11 Snow White. Do not get the ghastly "bright white" silicon caulk favored by plumbers who never have to see your bathroom again and choose their products accordingly. (One of the blog's readers noted that he found a sanded silicon caulk in the tile section of his local home improvement store -- and it was so cheap, he bought three tubes in slightly different shades to test out.)
  • A caulk gun. They're cheap. Don't even think about trying to apply this type of caulk without one; it requires a fair amount of strength even with one.
  • A box of thin, clear, cheap vinyl gloves from your local drugstore. They come 50 to a box, and you'll need about half of that. Be sure the gloves fit your fingertips snugly — loose fingers on the gloves will result in jagged lines when you try to smooth the caulk.
  • Three large, sturdy paper grocery bags or paper shopping bags — line all three with plastic garbage bags.

DAY 1: Cleaning and prep steps

  • Strip the old, mildewed rope of caulk from around the tub using the plastic scraper and metal pick or skewer. Remove any and all clinging caulk or film of caulk using the razor blade. Be thorough, because your new caulk won't adhere where there's old caulk, and if it won't adhere, then water will get through. And be careful, because the razor blade can gouge the finish on a non-porcelain tub.
  • Check the grout that was underneath the old caulk. Remove any extremely loose, crumbling grout from between wall and tub, particularly if it is severely mildewed. [Note that if the space between the tub and the wall, revealed when you remove the old caulk, is much more than 1/8", you may not be able to fill/cover it effectively with the new caulk. If so stop what you are doing, go to the tile shop or tile section of your home improvements store, and get some grout — the plain, non-acryllic stuff that you mix with water is easiest to deal with. Add a half day to your schedule, so after you have finished all the cleaning steps, you can apply the grout and let it dry before you start caulking.]
  • Dress in old clothes and put on rubber gloves. 
  • Use the Good Stuff Dawn dishwashing liquid to clean all mildew from tub walls, tile grout, and any gaping areas between the shower wall and the tub. This takes about 20 minutes, and includes scrubbing with the brush, letting the cleaner set, and rinsing the cleaner off. After this is rinsed, the dark mildew stains should disappear, or at least fade to a pale gray. If this loosens more mildewed old grout, remove that, too.
  • If you still have dark stains in the grout, use vinegar. Apply soak wads of paper towels in vinegar and use blue painters tape to tape them to the tile around the grout. Make sure the paper towels stay soaked in vinegar. After 2 hours, remove the paper towels and rinse with water.
  • If you still have mildew stains on the grout, use Oxyclean. Repeat the paper towels treatment, this time using Oxiclean (not chlorine) bleach. After 2 hours, remove and rinse area thorough.
  • Now, allow the area to be caulked to dry thoroughly. This may involve running the bathroom fan overnight. Drying time depends on your climate conditions, but plan on 12 to 24 hours. If you have pets, lock them out of the bathroom so they won't try to lick tile that has been cleaned using various chemicals.
  • [Optional grouting step] If you have gaps in the old grout that need to be filled with new grout, prepare by taping some plastic sheeting over the tub so you won't accidentally get grout on the tub. (Do not skip this step.) Then mix up about two cups of grout, following the manufacturers' directions, to create a thick grout paste. Use a paint spatula or popsicle sticks to pack grout into the gaps and smooth it down until it matches the adjoining grout. It should be slightly recessed below the level of the tile. Clean any grout off the tile or tub with a paper towel soaked in vinegar. Remove the plastic sheeting or other tub protection.
    Taped tub

  • While you are waiting for the grout to cure (at least 12 hours), you can tape the area to be caulked, leaving 1/8" of tub rim exposed and 1/8" - 1/4" of the tile wall exposed. I use 1" blue masking tape on the tub and wider blue masking tape on the tile wall. See photo. (Note that I've also taped about six inches up each corner of the tub.)

Caulk gun, loaded

DAY 2: Step-by-step caulking:

  • Make sure you have an uninterrupted 30 minutes to do the caulking. Once you start, you can't pause in the middle. If you do stop, the caulk will firm up while unsmoothed and the tub/wall seam will not be adequately sealed against moisture -- and you'll have to strip it off and start all over again.
  • Place beside the tub: The box of vinyl gloves, the grocery bag lined with a trash bag, and a small plastic container or very small bucket containing water with a little liquid dish detergent mixed in.
  • Apply the caulk bead using the caulk gun. (I found that sitting cross-legged in the tub helped me apply the caulk evenly.)
  • Apply the caulk sparingly. I tend to apply too large a bead. Something that reminds you of a clothesline cord is about right. If it starts to look like a rope, it's too much. You may also want to caulk a few inches up the inner corner (or corners) of the shower walls.
  • Once the caulk in is place, you are ready to smooth it. 
  • Using a series of vinyl gloves and dipping your fingers in soapy water, begin smoothing the caulk bead. Use a light touch. If the glove gets gunky with caulk, put on a new glove. Otherwise, your gunky glove will start sticking to the caulk and you risk pulling caulk away from the tub. Keeping peeling off sticky gloves into grocery bag and using new ones.
  • As soon as the the bead is smoothed and concave, remove the blue tape from the tub side of the caulk line and dump the tape into the grocery bag. There will now be a bit of a raised edge on the caulk where the tape was removed. Get out a glove, dip it in the soap, and start smoothing that border flat. You can use a firm touch, but don't squish the center of the bead that you already smoothed. Then remove the tape from the wall side of the caulk, and smooth that border.
  • Get out of the tub, recap your tube of caulk using plastic wrap and tape. Dump the bag of trash.

DAYS 3 AND 4: Drying

To ensure that the caulk cures completely, wait 72 hours before showering or otherwise allowing the caulk to get wet. (I've been known to sneak in a bath during the drying period, but use your own judgment. Washing the dog, for instance, is a bad idea.)

Enjoy. Save these directions for when you need to replace the caulk again — probably about two years from now.
Finished caulking


  1. Anonymous11:41 PM

    Thanks so much. These are the step by step instructions I was hoping for. That I did not get at the hardware store. Again, thanks so much for sharing your experience and enlightening us all.

  2. Anonymous8:03 AM

    Sharing your journey online was a very brave and courageous thing to do. Many thanks from and those of us who live the same private hell with no support groups to turn to. Tub caulking is not a subject that can be discussed with people who haven't been through it, and there is no 12-step program to help us.

    Your journal on subject has saved our sanity and marriage.

    Your story assured us that we are not alone, and we cannot thank you enough for posting the pictures. GOD BLESS YOU!!

  3. Anonymous6:46 PM

    I would add that you should fill the tub about 3/4 of the way with water before caulking so as to force it to sink to its lowest point to prevent the caulk from separating when someone takes a bath for the first time post-caulking.

  4. About filling the tub:
    Excellent point! However, it's most applicable if you have a somewhat flexible fiberglas tub. Those that are enameled steel don't rise or fall with the addition of water.

  5. Anonymous9:55 AM

    THANK YOU, THANK YOU!The masking tape idea is brilliant and just the solution I needed. Now, a dreaded job previously, has me racing home tonight to begin the project.

  6. Just wanted to leave some thanks - this gave me the confidence to DIY this project, after my caulk has been falling off (and was off in places) for a month. I didn't get perfectly smooth lines, but not bad for my first attempt. And I didn't work fast enough, so the second tape removal pulled some of the caulk off, but I wet my finger and it seems OK. Now I have to shower at the gym for the next four days.

    One thing I found helpful - if your lines get a little messed up on the second smoothing, you can kind of scooch them back with the scraper and smooth them out again.

  7. Very detailed and helpful. How long did your new edge last?

  8. Structurally, the most recent one lasted three years. No cracking or peeling! However, I have a very damp bathroom in the damp climate. In the spring and fall, when the heat is not on much in the house, it's difficult to get the shower to dry quickly, particularly if there are a few people taking showers during the day. So, on the third year I started to see some black mildew that won't come off, even with bleach cleaners. Time to do another round of caulk

  9. Anonymous1:54 PM

    Where did you buy your Color Caulk Premium Tile & Fixture Caulk?

  10. Anonymous10:24 AM

    I think this article will help us immensely. We cannot get our caulk to stick to our bathtub/showers. Since it's being applied to 3 different materials, we're assuming it not dry when we use it. It says 36 hours cure rate, but we're wondering if since we're in Florida is the humidity getting to the caulk? Should we be running a heater in the room during the drying/curing time?? We are using polyseamseal Everbright on polystyrene, ceramic tile and some other shower bottom. It's old so we're not sure what its made of.....

    I am pretty certain that grouting right after cleaning with alcohol has been causing our problem. We'll give it another try....

  11. Anonymous7:09 PM

    I wish I would have found your helpful article BEFORE re-caulking (I'm now looking for hints on how to remove smeared caulk from the tile). One helpful thing I did was to tape up a plastic drop cloth so we could continue to use the shower since we only have one shower in our house. I used duct tape to attach the plastic drop cloth around the top of the shower area and several pieces of tape to secure it at the bottom. After showering (or when you're ready to work on the area again), just roll up the plastic and clip it at the top.

  12. Anonymous10:26 AM

    Whats the most important ingredient to look for in the grout cleaner ? This brand Good stuff seems to be no longer around..

    And would you be safe just any item from any tile store instead of a homedepot or lowes ? (ie any national hardware store?)

  13. Anonymous9:30 AM

    Thanks so very, very much for this!