Cracks in the seams of your shower occur from the regular expansion and contraction of walls due to changes in temperature and humidity. Tub seams are even more vulnerable because most tubs flex when you step into them. Recaulking with a silicone or water-based caulk provides the best long-term protection. These products are long lasting and highly elastic. If you are doing only one shower, a 2.8-fluid-ounce tube is quicker and easier to handle than a cartridge in a caulking gun.
1. Prepare the shower. Clean all soap residue and mildew from the walls. Use a knife to dig the old caulk from corners and tub seams.
2. Apply the caulk. Cut the applicator tip so that the opening is 1/8 inch in diameter. Apply a continuous line about 3 feet long.
3. Smooth the line. Silicone becomes tacky fast, so smooth the first line with your finger as soon as you lay it. If the caulk should flow around the sides of your finger, immediately wipe away the excess with a soft cloth. Use warm, soapy water and your finger to re-form the joint.
4. Wait at least 12 hours before using the shower.