Caulking Tubs and Showers

The cracks that commonly appear around a shower or tub are caused by the weight of water and bodies forcing the floor to sink with every use. When the tub is empty again it returns to its original level, leaving cracks in the grout and caulk joints. To fix this problem and compensate for future movement use a flexible silicone caulk to fill the seams.

Scrape Cracked Caulking from Seams

First, remove any cracking or loose caulk. If the caulk is very loose and coming away at the edges it may be possible to remove most of it by running a putty knife under the bead as you pull it free. In other cases the caulk may be cracking but not coming off very easily. To remove stubborn caulk like this, begin by working a wooden scraper back and forth along the seam to remove as much as will come free.

Old caulk can be scraped off of ceramic tile and porcelain with a metal putty knife or razor–blade scraper, but fiberglass tubs and showers should be treated with wood or plastic scrapers to avoid damage to the finish.

Soften the Remaining Caulk

When all the loose caulk is removed soften what remains on the surface and in the seams. For silicone caulk, use denatured alcohol to liberally soak a soft, absorbent rag and use it to wet the caulk and surrounding area. Let the solvent sit on the caulk for a couple minutes and then use the rag to rub off as much clinging caulk as will come free.

Scrape and Scrape Some More

Soak the rag again, wrap it around a wooden stick and use it to force the rest of the caulk off. This can take a while and repeated soaking with a fresh spot on the rag.

The Final Cleaning

If there's residue left on ceramics or porcelain, a razor–blade glass scraper and steel wool can be used to finish cleaning the surface. If you're dealing with fiberglass or metal parts use a plastic kitchen scrubber to remove the last bit of residue. To finish, clean the seam to be caulked with denatured alcohol and let it dry for about 10 minutes before re–caulking.

Re–Caulk the Seam

You can buy tub and tile caulk in a tube that resembles a toothpaste tube or a cylinder that will fit into a caulk gun. Cut the applicator tip at a 45° and pierce the seal at the base using a long nail or the piercing pin on some caulking guns. Soak an old, cotton t–shirt or similar cloth in water and wring out the excess.

Don't stand in the tub or shower while re–caulking to avoid overfilling the gap. Begin caulking at one corner and fill the gap moving to the next corner. To make monitoring flow easier pull the caulk gun along, rather than pushing, while squeezing to dispense caulk. Go slowly enough to allow the caulk to fill the gap while not overfilling.

Smooth the Caulk Bead

Wet your index finger with water and use it to smooth the caulk along the seam while pushing it deeper into the gap.

Keep it Clean

Wipe the collected caulk from your finger onto a water–soaked rag to prevent spreading it to unwanted places.

Let the New Caulk Set

Allow the caulk to set for an hour or two before touching it. For more caulking tips see this tutorial.