How to Repair a Fiberglass Shower

Fiberglass or acrylic bathtubs and showers are easy to install and are often less expensive than other options, such as a cast-iron tub or ceramic tile shower stall, making them a favorite for budget-conscious homeowners.  

Over time, acrylic and fiberglass surfaces can get dented or cracked, often because of the flexing of the walls or of impact that can dent, crack, or punch holes. A variety of options are available at this point, including outright replacement of the bathtub or shower or installing a new liner inside the old tub or shower.

But one fast and cost-effective fix is to fill the crack or hole using a fiberglass/acrylic repair kit. These materials include epoxy-like materials similar to the compounds used as filler in automobile body repairs. You can even use an automotive body filler to make repairs on tubs and showers, sinks, or toilets.

Before You Begin

Rather than using automotive body filler, though, a better choice is to buy a repair kit that is factory-matched to your tub or shower.

These kits have filler paste already tinted to match the color of your fixture and will include much of what you need to make the repairs—only a few extra tools and materials are required. A single kit may provide enough material to make several repairs. The color will be close to that of your shower or tub but rarely will it be an exact match.

There are many repair and resurfacing products available, so make your choice carefully. For simple cosmetic repairs, most people find that a paste-type fiberglass/acrylic kit is easier to use than a spray product. Paste kits typically include: 

• Base coat paste and catalyst
• Lightening and darkening toners
• Rubbing compound or buffing bar
• Wet/dry sandpapers
• Clear top coat that is sprayed or brushed on at the end

Safety Considerations

This repair uses an epoxy-type filler that has hazardous fumes. Good ventilation is required, as well as the use of an approved ventilator mask. Always follow the kit manufacturer's recommendations for safety measures.

You Will Need

Materials

• Acrylic/fiberglass paste-type repair kit, color-matched to your fixture
• Nail polish remover or acetone

Tools

• Utility knife
• Utility knife blades
• Power drill with small drum sander or grinding disks or a car buffer
• Wet/dry sandpapers (220-, 320-, 400-, and 600-grit)
• Scouring pads
• Clean cloths or paper towels
• Heat gun
• Buffing cloth
• Protective gloves
• Ventilator mask

Instructions

1. Open up Crack

   Use a sharp utility knife to carve out a V shape around the edges of the damaged area. Make sure to cut down through the color layer of the acrylic or fiberglass into the structure below. Usually, this means cutting down between 1/16- and 1/4-inch.

   If the surface is very hard or the damaged area is very large, a sanding drum or grinding disk attached to a drill or Dremel tool will make this preparation easier. Angle the sides of the damaged area so that the filler paste can be applied smoothly.

2. Roughen Surface Area

   Wipe the surfaces clean with cloths or paper towels, then use 220-grit sandpaper to slightly roughen the entire repair area. This slight roughening will help the paste adhere to the damaged area. Do not use sandpaper rougher than 220-grit or it will later be difficult to smooth it out again.

3. Clean Area

   Clean the repair area with nail polish remover or acetone.

   Warning

   From this point onward, make sure to ventilate the area well and use a ventilator mask. Wear protective gloves for these steps. Wear eye protection.

4. Mix Ingredients

   Transfer a small amount of paste filler from the kit into one of the provided mixing cups. If necessary, use the lightening or darkening toners to adjust the color to match your tub or shower. This is often necessary with white tubs or showers.

   Add the catalyst agent to the paste in the ratio recommended by the manufacturer. Mix the ingredients together thoroughly to form the activated filler paste.

5. Apply Paste to Damaged Area

   Apply the activated paste mixture to the repair area using the mixing stick provided in the kit. Make sure to fully fill the damaged area. Overfill the patch area slightly; it will be sanded flush later. 

6. Let Paste Harden

   Allow the paste to fully harden for one hour, or according to the kit instructions. While a heat gun can be used to speed up this drying time, it's usually best to let it dry and harden on its own.

7. Blend Repair Area

   Use wet/dry sandpaper to blend in the repair area with the surrounding surface. The best results are achieved if you sand in several stages using progressively finer grits of wet/dry sandpaper. Begin with 220-grit, then proceed by sanding with 320-, 400-, and finally 600-grit sandpaper. As you sand, drip water onto the sanding area with a wet rag to lubricate the surfaces.

8. Polish Repair Area

   Clean away the sanding dust, then use the rubbing compound included in the kit to polish and blend the repair area with the surrounding material.

   High-speed buffing will give the best results—a buffing bonnet mounted to a drill or an automotive buffing tool is a good choice. If you have a car polisher, this will work better because it is ergonomically designed for polishing. Keep the speed low, though, to avoid melting the plastic.

   Use 600-grit paper. You can even cut out a kitchen scouring pad and attach it to the buffer. Be careful not to let the edges of the buffer head touch the tub/shower surface.

9. Apply Clear Coat

   If your kit includes a clear top-coat layer, apply it now, according to kit instructions. 

When to Call a Professional

Do-it-yourself repairs to fiberglass showers and tubs can be quite effective from a functional standpoint. Aesthetically, though, it's difficult to color-match the repair to the rest of the shower unless you have a large set of dyes to work with.

You'll even find that one type of white in the repair kit may not match the white of the shower or tub. This issue is compounded by the fact that shower and tub surfaces change colors over time, sometimes lightening and sometimes darkening.

Call a professional for expert color-matching of filler to tub/shower surface. You'll also want to call a professional for any large cracks or holes that extend several inches or more.