How to Seal a Cracked Fiberglass Bathtub

Written by richard toole
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How to Seal a Cracked Fiberglass Bathtub
Repairing a bathtub crack yourself will save you from calling a contractor. (Jupiterimages/ Images)

Fibreglass bathtubs are fairly durable, but over time and with constant use they can crack or become damaged. At first glance you may think repairing a bathtub crack is over your head, but it really is not. As long as you have a small sanding tool and some fibreglass material and adhesives to work with, you can save a money by doing the work yourself.

Skill level:

Things you need

  • Rag
  • Safety glasses
  • Dust mask
  • Gloves
  • Long trousers
  • Long sleeves
  • Rotary tool with 40-grit disc sander attachment
  • 80-grit sandpaper
  • Vacuum
  • Epoxy
  • Duct tape
  • 9-oz. fibreglass cloth
  • Fibreglass resin
  • Paint

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  1. 1

    Place a towel over the tub drain to prevent it from clogging with debris.

  2. 2

    Put on protective gear to avoid getting tiny glass shards from the fibreglass on your skin or in your eyes. Avoid inhaling any of the particles as you sand the tub. Wear a pair of safety glasses, dust mask, gloves, long trousers and long sleeves.

  3. 3

    Widen the crack for a better bond to the tub if the crack has more surface area to which to adhere. Use a rotary tool such as a Dremel with a 40-grit sander attachment to widen the crack. You want to widen the crack about 12 times the thickness of the tub's laminate. Most bathtubs have a laminate thickness of 1/8 inch, so use the sander to widen the crack to 1 1/2 inches.

  4. 4

    Vacuum all of the dust out of the damaged area and the rest of the tub. Smooth the inside of the crack with 80-grit sandpaper, using your hands, not the rotary tool. Vacuum inside the crack again.

  5. 5

    Tape around the crack with duct tape. Place the duct tape on the surface of the bathtub that borders the crack so you frame the crack and prevent accidentally getting epoxy or resin on the tub's surface.

  6. 6

    Cut several pieces of 255gr. fibreglass cloth to the proper size to fill the crack. A typical 1/8-inch-thick laminate bathtub will require four or five layers of 255gr. cloth.

  7. 7

    Apply a coat of fibreglass resin to the inside of the crack, then coat the first layer of fibreglass cloth with fibreglass resin. Apply resin to both sides of the fibreglass cloth, then place it inside the crack. Repeat for the remaining pieces of fibreglass cloth until the crack is level with the tub's surface. Allow to dry overnight.

  8. 8

    Apply a layer of epoxy to the surface and around the edges of the top piece of fibreglass cloth. This will help smooth out the cloth layers. Allow to dry overnight.

  9. 9

    Match the pigment of the last epoxy layer with your bathtub. If your tub is white, a simple adhesive filler will turn the epoxy white. Match the colour of your tub with an appropriate epoxy paint colour applied to the top of the crack area. Allow several days for the epoxy to cure before using the bathtub.

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