How to Repair a Crack in a Plastic Shower Stall

You can repair a crack in a plastic shower stall using a tub and shower repair kit, which usually consists of two-part epoxy paste, fiberglass cloth and sandpaper. The procedure is not difficult or complicated, but before you undertake it, you have an important assessment to make, and in some cases, a little extra work to do before you do the actual patching. You want to assess the likelihood of the crack spreading once you make the repair, and if it's on the shower base, the likelihood is high, so you'll want to add extra support to prevent that from happening.

The danger of a crack spreading is small if it's on the shower wall, and it was caused by an impact or if it's a spider crack that hasn't penetrated all the way through the plastic. In that case, you can proceed with the basic repair procedure using your store-bought repair kit:

1. Clean the area around the crack thoroughly using isopropyl alcohol and a rag.
   
   
2. Mix the epoxy paste in the kit with the hardener according to the instructions.
   
   
3. Trowel the paste into the crack with a putty knife, taking care to remove as much of the excess as possible.
   
   
4. Wait for the paste to set and then sand it flat with 400-grit sandpaper, which is usually provided with the kit.
   
   
5. Restore the sheen by applying a little automobile wax and buffing it up with a buffing cloth.

Some epoxy products contain high concentrations of volatile organic compounds (VOCs), so provide plenty of ventilation, and if you're sensitive to VOCs, wear a respirator.

Cracks on the shower base and near the door hinges are subject to stress and will probably continue spreading after you patch them. To prevent this, drill a stop-drill hole at each end of the crack using a drill and a 1/4-inch drill bit. You can usually fill 1/4-inch holes with epoxy paste, but to be on the safe side, it's a good idea to lay a small piece of fiberglass cloth over each hole after you've applied the paste and recoat with a little more paste. When the paste sets, apply one more coat and then sand and polish.

If you're repairing a crack on the shower base, there's a good chance it occurred because there isn't enough support under the base, and the crack will spread even if you drill stop-drill holes. One way to provide this support is to drill a series of 1/4-inch holes around the crack and inject spray foam, which will expand and solidify to support the base and prevent flexing. Be sure to use a high-density, nonexpanding foam, such as Great Stuff window and door sealant, and wear disposable clothing because foam is impossible to remove from fabric.

A more professional way to provide support is to inject tile grout or mortar using a manual cement caulking pump. Drill a series of holes around the crack that are large enough for the pump nozzle, mix the grout or mortar to a soupy consistency and inject it into each hole until it starts backing out of the hole. Unlike foam, neither grout nor mortar will expand or get stuck on your clothes. When the material sets, patch the crack with your repair kit.