How To Fix Hairline Crack In A Fiberglass Tub

Eli Smith
by Eli Smith

Anytime you have a hairline crack in your fiberglass tub, it can be a frustrating experience. You may be wondering how long it will take before this crack turns into a much larger issue. So, how do you fix a hairline crack in your tub?

  • Purchase a fiberglass tub repair kit.
  • Clean the area of any dirt or grime.
  • Mix the resin and fill in the crack using a toothpick or popsicle stick.
  • Wait as long as it takes for the mix to dry.
  • Use sandpaper to ensure that the tub is the right shape.
  • Paint (if needed)
  • Run water to test if your repair is effective.

Below, we will get into the details behind the steps listed above. These steps will work for any fiberglass tub repair kit. Be sure that you clear an entire day where people won’t be using the shower.

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Step One: Purchase A Fiberglass Tub Repair Kit

Your local hardware store will carry a variety of tub repair kits. Check out Amazon if you don’t have a local option. Otherwise, you can use Home Depot, Lowes, or Ace Hardware with success.

While the repair kit will contain most of the items you need, be sure you have everything in this list below before starting the repair:

  • Epoxy or polyester resin
  • Hardener
  • Mixing stick
  • Soft paintbrush
  • Small container for resin
  • Paint to match the tub
  • Household cleaner
  • Sponge
  • Rag
  • Safety gloves

Remember that a hairline crack typically means that your damage is less than a 1/4th of an inch wide. Any wider and you will need to purchase a patch.

Step 2: Clean The Area

Your next step In any repair process is to ensure that the area is clean before your start. Trapping any dirt or grime inside of your tube can be disgusting.

Also, if there is an air pocket remaining, it will be easier for this to happen again. By ensuring you have a clean workspace before beginning, you avoid this issue.

Step 3: Mix The Resin And Fill In The Crack

Be sure you have your gloves on for this part.

Follow the instructions on the package to ensure you have the right balance of resin and hardener. Too much or too little will result in a failed hardening.

If it cannot harden, you will have to dig out and reclean the surface before purchasing some extra resin and hardener.

Both an epoxy and polyester resin will work. If you use epoxy, ensure that it is clear before using it. If you don’t, it may discolor your paint.

Step 4: Wait For The Mixture To Dry

Whether you use epoxy of polyester, it takes a great deal of time to dry. This process can take up to three days when using epoxy, but there are methods for drying quicker.

When choosing the polyester option with a fiberglass repair kit, it can take around 24 hours to dry. Check the package instructions for details

Once the mixture is dry, you can move onto the next step. Suppose you try and jump ahead to the next step. In that case, you run into the mix deforming, causing potential air pockets of cosmetic problems.

Step 5: Sand The Surface

Once you have waited a sufficient amount of time for the resin mixture to dry, you can sand down the surface to ensure that everything is even.

In some cases, you will have to apply an additional layer of putty. However, this is typically unlikely for most fiberglass repair situations. If the issue is limited to a hairline crack, It should only require a small resin amount.

After sanding, you will have to wait to ensure that the sanded portion’s underside can dry. You will have potentially exposed softer material at this point.

Step 6: Paint (If Needed)

If your resign is colorless or doesn’t match your tub, you will need paint over the surface to ensure the colors match. In the best-case scenario, you should take a piece of your tub to a hardware store that can match paint.

However, chipping off a portion of your tub isn’t a good idea. It means that you’ve turned your hairline crack into something significant. As a result, try and see if you can’t find if this tub is standard among bathroom projects.

Once you locate the company’s exact tub, they should provide specifications at what type of paint they use. If all else fails, take a picture and bring it with you to the hardware store.

Step 7: Test The Repair

After the paint is dry and uniform, your last step will be to test out its effectiveness. You can do this by running a hot shower or bath while keeping an eye on this gap.

If the gap appears to be re-appearing, the mixture you used did not dry properly. If your paint is running off, you did not give it an ample amount of time to dry.

If you followed the instructions directly, there might have been an issue with that batch of resin. You should contact customer service for details. Otherwise, you can typically purchase just the polyester resin by itself over the counter.

What Causes A Fiberglass Tub To Crack?

A fiberglass tub can crack due to three different reasons

  • Age
  • Stress
  • Stronger cleaners

It is only natural for a bathtub to crack over time due to age. The more you use your bathtub, the quicker it will age.

If age is causing regular cracks, you may want to replace your bathtub. Check out our guide on bathtub replacement in that case.

Stress cracks come from when you drop or rest a heavy object on your bathtub. In combination with these other issues, this can lead to severe damages.

Also, the use of strong cleaners is excellent for making your bathroom maintain its freshness. But stronger cleaners, such as bleach, will cause your bathtub to age faster. These cleaners can also wear down the finish of your tub.

A hairline crack should not be more than 1/4th of an inch. Any further and the damage is likely more profound than you may expect.

How Much Does It Cost To Fix A Cracked Tub?

The deeper the crack, the higher the cost.

For hairline fracture, you are not likely to pay more than $50. Fifty dollars is the typical cost of most repair kits.

With larger cracks that will require the injection of material, you can spend up to $100 for the materials needed to repair. Include labor, and you can expect this project’s cost to get as high as $300.

This price can vary heavily depending upon your location. A plumber living in the middle of nowhere may be willing to charge more based on scarcity. You can say the same if you have more competition, so don’t be afraid to shop around and compare pricing.

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Related Questions

How To Fix Hairline Crack In Plastic Tub?

There is virtually no change between repairing a fiberglass and plastic tub. Be sure to use either polyester or epoxy resin, give it time to dry and sand it down when done, and paint over the tub to ensure the color matches.

A fiberglass tub repair kit is also applicable in this situation. Many times they do not limit tub repair kits to specific types of material.

How To Repair A Hairline Crack In Acrylic Tub?

Much like repairing a plastic or fiberglass tub, the instructions remain unchanged. Mix polyester resin, wait for it to dry, sand it down, and paint the section to be sure it matches.

Will Flex Seal Fix A Cracked Bathtub?

Flex seal is useful for hairline cracks. But it is a bit overkill when it comes to application, so we would suggest that you use repair kits intended for this.

When looking at larger cracks, do not use flex seal. Larger cracks will require something that has a bit more structural support. Small crack seal kits and flex seal do not have any structural value.

In this case, larger cracks will require something to be injected typically.

Eli Smith
Eli Smith

I'm a guy who becomes the expert of whatever I stumble upon, writing-wise. I've written tons about cool home products, home improvement, and smart technology in the home. I'm also the proud father of a kiddo born on new years, making my holidays very busy.

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