How to repair a fiberglass tub

Fiberglass tub repair can seem very daunting, but if you have a drill, sandpaper, and glue, you can do it yourself.

Photo Credit: Suzanne Carter-Jackson
By Wayne Presnell

Fiberglass tub repair can seem very daunting, but if you have a drill, sandpaper, and glue, you can do it yourself.

The degree of the repair depends on the size of the problem, i.e. a small crack or a large hole. If it is a small crack, make sure your tub is clean and dry. You can use either a fiberglass repair kit and follow the instructions on the box, or, appliance touch up should work. Appliance touch up can be applied with a small brush and allowed to dry overnight. Or, you can use a hairdryer to speed up the process. If the problem is larger, it will take a little longer to finish the repair. Again, clean and dry the tub to see the cracks.

Larger cracks can be reached from underneath the tub or in the tub itself. Underneath the tub can sometimes work out better. This way, you can reinforce the bottom of a tub or shower while sealing the cracks.

If you can, go in from the ceiling, basement, or crawlspace. Break through the drywall or plaster, with a hammer and chisel. You should be able to see the cracks from underneath the tub, if not, and then try another way to repair the tub. Simply clean the tub, any tub cleaner will do, and sand it smooth with sandpaper; this will prepare the surface for the glue. Then, simply glue a piece of plywood, heavily coated with one of the high-density fillers, to the cracked area with any epoxy. Push the plywood in place until the epoxy sets. This bottom may be stronger than before, which is a good reason to go in from the bottom. In small curves where plywood will not fit well, you will have to apply layers of fiberglass and epoxy.

If you cannot work from underneath, then you need to work from in the tub. Again, clean the tub so you can see the cracks. Once you locate the ends of the cracks, take a drill bit, less then an 1/4 inch, and drill a small hole at the end of each crack. Next, take some insulating foam and fill up the small holes. The product will expand underneath the tub. It will dry hard, so do not over fill as it may expand and cause a bulge in the fiberglass.

Now use a polyester filler to fill in the cracks and holes. If you want to use a fiberglass repair kit, that’s fine too, but sometimes the resin in those kits will react with the repair coating. Using various sheets of wet sand paper, sand it down the polyester filler so that it is even with the tub. Now all you have to do is match the original color.

You can make your own epoxy gel coat (paint) from epoxy, acrylic paint, and color additives. Therefore, if you want to create a new color, or cannot match the tub’s color, this might be the way to go. On the other hand, if you have a regular color tub, most paint stores, and hardware stores carry colors already premixed and ready for you to use. As with any paints you try, you might want to ask your store about any additional drying time before the tub should be used.

To repair chips in the tub, that have not leaked all the way through the fiberglass, apply some polyester filler over the chip and let dry. Any filler that dries fast will do. Begin using various grits of sandpaper on the filler until almost smooth. Keep the sandpaper clean by rising and sanding every few strokes. Be careful not to sand or scratch the surrounding area. Finish out by sanding smooth with 400 wet sandpaper. For the closest color you can find to match, purchase a porcelain repair kit, not a fiberglass kit.

Next, you need to spray area with a portable sprayer. But before spraying, tape surrounding area to avoid over spray and wipe surface with alcohol. Follow directions on sprayer. After it has set, you can use a fine sandpaper to blend the area.

Your fiberglass bathtub and unit may just be scratched or discolored. The fiberglass unit can be refinished to any color. Clean it and sand it with wet sand paper until every bit of shine left on the surface is gone. You will need to take your time and use a lot of sandpaper. You may want to rinse your sand paper every so often. Fill all cracks and holes with a polyester filler and sand to smooth. Tape off all plumbing. The surface must be totally free of all dust, dirt, etc. Towel the surface off and let dry completely. Tape off any surrounding area you do not want painted, and use a High Volume, Low Pressure sprayer. Just before spraying, wipe surface down with cheese cloth, and any good laquer thinner. Then wipe surface with tack cloth. Apply a aliphatic acrylic urethane, a special type of paint that resists chipping, cracking and peeling, to the surface of the tub. Then start spraying. The surface will need 2 or 3 even coats. Let dry overnight.

During all these steps, be sure to wear gloves, a dust mask and goggles. Fiberglass dust can be very damaging to eyes and noses. In addition, if your bathroom has a fan, you might want to keep it turned on until the paint fumes have had time to get out of the air, and open any windows.