How to Repair a Fiberglass Shower Tub

A crack or a hole in a fiberglass shower tub makes the unit unusable and subject to a potentially expensive repair or replacement. This article demonstrates a do it yourself repair that is possible with moderate effort and modest cost.

Things You'll Need

• Fiberglass repair kit
• Marine plastic filler
• Gel coat
• Color tint
• Coarse sandpaper
• Wet-or-dry sandpaper
• Latex gloves
• Plastic wrap

Instructions

1. 

   Purchase the supplies. You will need a fiberglass repair kit with resin, hardener and fiberglass cloth. You will also need a marine grade plastic filler, a small can of gel coat,a coloring agent, 60 or 80 grit sandpaper, 220, 320 and 400 wet-or-dry sandpaper, latex gloves and plastic wrap.

2. 

   Vigorously sand the area of the hole or crack with coarse sandpaper. Also sand outward to about two inches around the perimeter of the damaged area.

3. 

   Cut three patches from the fiberglass cloth that comes with the kit. Make their sizes progressively larger, with the largest patch slightly smaller than the sanded area. In a shallow container, mix proportionate amounts of fiberglass resin with droplets of the hardener, according to the package directions. While wearing latex gloves, dip and saturate the smallest patch into the fiberglass mixture, and then apply it to the repair area. Layer the remaining two patches, from smaller to larger sizes, in like manner. Allow the repair to cure for several hours or overnight.

4. 

   Sand the hardened fiberglass with coarse sandpaper, being careful not to scratch the surrounding surfaces of the tub. Fiberglass is very hard and difficult to sand, so Formula 27 or equivalent marine plastic filler is recommended for the next stage of the repair. This compound cures to a softer material that sands easily, similar to automotive body putty, except it is more waterproof. This is also mixed with a hardener and cures in only 15 to 30 minutes. Apply a layer of the Formula 27 on top of the fiberglass, and sand it until you get a relatively smooth surface that blends into the surrounding tub area. Repeat this process if needed.

5. 

   The final stage is an application of gel coat, which is a fiberglass product that is milky in appearance and can be tinted to match your tub's color. Mix an appropriate amount of gel coat with tiny bits of the tint until you get a close color match. Then add hardener to this mixture according to package directions. Brush the gel coat on over the repair area about 1/8 of an inch thick. You then need to cover the surface of the gel coat with plastic wrap so that it will cure properly.

6. 

   Let the gel coat cure overnight, and then wet sand it with number 220 wet-or-dry sandpaper, to blend it in with the surrounding surface. You can then wet sand with the finer grades to improve the appearance of the repair area. Some remaining texture in the surface is okay, especially if it is on the bottom of the tub where some traction is preferred.

Tips & Warnings

• Consider using masking tape and newspaper to protect the area surrounding the repair.

• Insure that you have adequate ventilation when using the repair compounds.

• You may need a fan to ventilate the tub area plus open windows in an adjacent room.