It is usual for a fiberglass tub to develop small cracks. However, if you do not repair the small breaks early, they may expand and cause leakages and eventually, your bathtub could break apart. Fortunately, you can rectify your cracked fiberglass tub yourself.

Here is how to fix a crack on your fiberglass tub:

  1. Clean the surface and dry it.
  2. Sand the surface surrounding the crack.
  3. Mix and apply fiberglass resin adhesive.
  4. Sand the adhesive.
  5. Apply putty (fiberglass filler) to fill the crack.
  6. Sand the surface again.
  7. Apply epoxy coating.
  8. Put fiberglass clothing over the crack.
  9. Add more epoxy coating.
  10. Apply a finishing coat or sealer.

Besides, several other more complex methods exist that you can apply to fix cracks on your fiberglass bathtub. For a more expounded guide on how to use the simple steps highlighted above to repair your fiberglass tub, including tips on what causes the cracks and how you can prevent them, keep reading.

1. Clean the Surface and Dry It

First, prepare these materials that you will be needing to mend the crack:

  • A fiberglass bathtub repair kit
  • Paintbrush
  • A cleaning rag or sponge
  • A piece of lint-free cloth
  • Household cleaner
  • Emery cloth or fine(150grit) sandpaper
  • Medium (80grit) sandpaper
  • Rubber gloves
  • A pair of scissors.

Then, start with cleaning the area surrounding the crack. Use a rubbing alcohol wipe or a home-based cleaner and a sponge. Ensure you get rid of all debris, dirt, or mold from the dent and the surrounding surface. Then use a paper towel to dry the area.

2. Sand the Surface Surrounding the Crack

After cleaning the area, use the emery cloth or medium(80 grit) sandpaper to make your surface slightly rough. A rough texture will allow the adhesive and chemicals to bond effortlessly. Sand one to two inches from the crack. After sanding, remove the dirt using a piece of cloth or brush.

3. Mix and Apply Fiberglass Resin Adhesive

Use the instructions from the repair kit for the right proportion of mixing the adhesive components (resin and hardener). Mix more than required to ensure the contents mix thoroughly. After mixing, let the adhesive settle for three to five minutes.

Then use a brush to evenly apply the mixture to the dent and the surface around it. Make sure you cover at least one inch beyond the crack. Also, ensure the adhesive gets as deep as possible into the hole. Wipe any drip or residue and allow the mixture to dry for up to two hours.

4. Sand the Adhesive

After drying for two hours, sand the adhesive using medium (grit 80) sandpaper. Then lightly sand it again with smooth (grit 150) sandpaper. Sanding will help remove excess adhesive. Removing excess adhesive will make it easier for the fiberglass filler to bond in the long run.

5. Apply Putty (Fiberglass Filler) To Fill the Crack

Now, mix the filler from your repair kit. Follow mixing instructions from the kit. Then apply the fiberglass filler using the putty knife. You can alternatively use all-purpose putty mixed with cream hardener. Make sure you fill the crack with the chemical. Then remove all excess filler and allow it to dry for about fifteen minutes.

6. Sand the Surface Again

When the filler is dry, sand it again using an emery cloth or smooth (150 grit) sandpaper. Smoothen the whole surface, including the edges. Make sure the repaired area is at level with the entire surface. Be careful not to overdo the sanding and ruin the work.

Once the surface is smooth, wipe it with a paper towel and then tack cloth.

7. Apply Epoxy Coating

Then, prepare an epoxy mixture per instructions from the kit. Apply the mixture to coat the crack. Use a brush to spread the epoxy blend and make sure it covers up to two inches beyond the dent for better results. Also, ensure that the coating is even across the surface. Otherwise, you’ll end up with an uneven coating.

8. Put Fiberglass Clothing Over the Crack

Find fiberglass clothing from your kit. Measure the size of the crack, then cut a portion of the fiberglass cloth that can fit the area. Make sure that it overlaps the edges of the dent by one inch. Cover the patch with the material and press firmly while the epoxy is still wet.

Then using the putty knife, squeeze out trapped air bubbles from beneath the cloth.

9. Add More Epoxy Coating

After covering the crack with the fiberglass cloth, add more epoxy coating using a paintbrush. Spread the coat evenly to cover the dent and around its edges. Make sure you apply a larger but reasonable quantity of epoxy this round. Let it dry before you move on to the next step.

10. Apply a Finishing Coat or Sealer

The final step is applying the sealer to your patch. Your repair kit also contains the sealer, which waterproofs the repaired area and protects it from possibly harmful substances. I recommend that you restore your bathtub’s glossy finish with a buffing treatment after the sealer has dried.

You can apply this procedure in fixing all kinds of cracks in your fiberglass tub and even the fiberglass shower pan.

For the best results, make sure you select the appropriate fiberglass repair kit. The repair kit contains the chemicals and tools you require to mend a damaged or cracked fiberglass surface.

The kit comes with:

  • Brush
  • Fiberglass cloth
  • Hardener
  • Mixing stick
  • Resin
  • Mixing tray
  • Spreader

Two repair kit types are available:

  • Surface repair is for fixing outer surface cracks. This kit carries tape or polymer paint.
  • Internal repair; for repairing deeper cracks. It has glue or pastes that seal the cracks.

How deep the crack is determines the repair kit that you will use. You can use HT HOMETINKER Tub Repair Kit, available from Amazon. It is non-toxic, waterproof, easy to apply, and perfectly matches the color of your bathtub, leaving no traces of repair.

Causes of Cracks on a Fiberglass Tub

Fiberglass tubs are cheaper to buy and maintain and are preferred by many homes. They are attractive and easy to repair and install. However, you can easily break them if you are not careful.

Fiberglass can easily bend under weight because it is very flexible. Improper support and pressure from frequent use and harsh cleaning detergents can cause cracks after some time. Also, dropping heavy objects in the bathtub can cause dents and small divots.

Let us look at some of the most common causes of cracks in fiberglass bathtubs.

Accidental Dropping

Fiberglass is one of the lightest bathtubs. You can easily carry it anywhere. Hence, the risk of dropping it is high. How deep the crack is will determine whether or not you can fix it yourself. If the dent is not so deep, you can repair it yourself.

If it gets through the thickness of the tub, you may need a professional to help you fix it. It is advisable not to move your bathtub once installed to avoid damaging it.

Heavy Objects

Perhaps you have decorative items near your bathtub like a flower vase, a fragrance candle, or a statue. Or you may be having a shower caddy made from metal or any other accessories. Such items can hit and crack your tub if they fall accidentally.

Luckily, you can repair the stress cracks because they only damage the surface. To prevent accidental damages, I recommend that you keep heavy objects far from your bathtub. You can arrange your ornaments on the bathroom shelf rather than keeping them on the window.

Improper Support

During installation, your fiberglass tub requires sufficient support. Without proper mounting, your body weight and that of water may press the weaker points and lead to the formation of cracks.

It can be helpful to ensure that your bathtub has proper support by an even ground to enhance its stability and prevent cracking.

Using Abrasive Cleaners

Bacteria, hair, dirt, and soap scum stick in the bathtubs and create stubborn stains that don’t wash off easily. In an attempt to clean them, you may use substances like heavy-duty cleaners, ammonia, and bleach. Such cleaning chemicals weaken your tub’s finish making it easier to crack.

It is recommendable to use mild cleansers with a soft-bristled brush while cleaning your bathtub. Avoid ammonia, bleach, or any detergents that contain acid. If the stains are persistent, you may seek professional cleaning advice.

I recommend Black Diamond Scum Remover Spray. It contains no ammonia or phosphate and is biodegradable, acid-free, and non-toxic. Also, it removes stubborn stains and soap scum.

Normal Aging

Bathtubs weaken over time due to wear and tear from normal usage. The surface wears slowly and continuously. Eventually, the tub becomes thin, and cracks may start developing. If your tub cracks due to old age, I recommend replacing it because fixing it may not sustain it for long.

Final Thoughts

Fixing a crack in a fiberglass tub is an easy task. You can perform yourself. If you have one in your home, you need to invest in a repair kit and be ready to fix any cracks as soon as you see them. Besides, I hope you found this guide helpful, and you will apply these steps and tips to mend and prevent breakages to your bathtub.

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