A poorly caulked bathtub is one of those things that starts as a cosmetic issue and turns into a water damage problem. Water gets behind the wall through gaps in old caulk, stays there, grows mold, and eventually damages the drywall or subfloor. Recaulking takes about two hours and a $5 tube of caulk. The alternative is a bathroom renovation that costs thousands.
- Remove all the old caulk first
- Choose the right caulk Use 100% silicone caulk or a siliconized latex caulk specifically labeled for kitchen and bath use. These contain mold inhibitors and are designed to flex with the natural movement between the tub and wall without cracking. Standard latex caulk dries rigid and will crack within months in a wet environment. White is the most common choice for bathtubs, but clear works well against dark tile. If you are matching existing grout color, bring a photo to the hardware store. The tube will typically be either a screw-top or require a caulk gun. A basic caulk gun costs $5 and gives you much better control than the squeeze tubes, especially on longer runs. Fill the tub before you caulk
- Apply the caulk in one smooth pass
- Let it cure properly
The most common mistake is applying new caulk over old caulk. It does not stick well, it looks bad, and the underlying problems stay. Removing the old caulk completely is the most important part of the job.
Remove all the old caulk first
Use a caulk remover tool (a plastic or metal scraper designed for the purpose, about $5) to score and peel the old caulk away from both the tub surface and the tile or wall surface. A utility knife works too, but be careful around tile grout. Get every bit of the old caulk out, including the soft sections that look fine. You want a completely clean joint.
After removing the caulk, clean the joint thoroughly. Any mold, soap scum, or residue will prevent the new caulk from bonding properly. Spray the joint with a mixture of one part bleach to ten parts water, let it sit for ten minutes, and scrub with an old toothbrush. Rinse and let the area dry completely. This is critical: caulk applied to a damp surface will fail quickly. Give it at least four hours to dry, or use a hair dryer on the joint if you are in a hurry.
Choose the right caulk
This is the trick most guides skip. Fill the bathtub with water before applying the new caulk and leave it full until the caulk cures. The weight of the water expands the tub slightly and pulls the gap between the tub and wall to its widest point. If you caulk with an empty tub, the joint is slightly narrower than it will be when the tub is in use. When someone fills the tub after your repair, the expanded joint stresses the fresh caulk and it cracks. Caulking with a full tub prevents that.
Apply the caulk in one smooth pass
Cut the tip of the caulk tube at a 45-degree angle. Start small, you can always cut more off, but you cannot put it back. A smaller opening gives you more control. If using a caulk gun, puncture the inner foil seal with a long nail or the puncturing tool on the gun handle.
Hold the gun at a 45-degree angle to the joint and move steadily in one direction, applying consistent pressure on the trigger. Move at a pace that keeps a small bead of caulk just ahead of the tip. Work from one end of the joint to the other without stopping if possible. Stopping mid-run creates lumps where you restart.
Apply the full length of one joint, then tool it immediately before it starts to skin over. Tooling means smoothing the caulk into the joint with a wet finger or a caulk tooling tool. Dip your finger in water first to prevent sticking. Run it along the bead in one smooth pass, pressing the caulk into the joint and removing excess. Wipe the excess on a damp paper towel as you go.
Let it cure properly
Silicone caulk needs 24 hours to cure before exposure to water. Do not use the shower or tub during that time. The tub can be drained after the caulk has skinned over, usually after about an hour, but do not run water over the fresh caulk until it has fully cured.
Once cured, the caulk should be smooth, firmly adhered to both surfaces, and slightly flexible when pressed. Any sections that look thin, have gaps, or are not adhered on one side should be removed and redone before water gets a chance to get behind them.
A tube of caulk costs $5. A bathroom water damage repair costs thousands. That math is about as clear as it gets. For more ways to protect your home budget and track where your money goes, the Family Budget Reset is a $22 guide that helps families get a clear picture of their finances in 30 days.
