Why Is My Bathtub Cracking: A Step-by-Step Guide on How To Fix a Cracked Bathtub

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Bathtubs are a luxurious item to have in your home, but like everything else, they require maintenance in order to keep them looking and functioning their best. Bathtub cracks are not only unsightly, but they can be potentially dangerous and costly in the long run. This answers your question, why is my bathtub cracking?

In this blog post, we want to show our readers what causes bathtubs to start to crack and what the most common types of cracks are. We will also provide a step-by-step guide on fixing a cracked bathtub and how much it costs to repair these cracks. Finally, we will cover how to maintain your bathtub so that you can prevent any future cracks from occurring.

So don’t run out and buy a new bathtub just yet!

Why Is My Bathtub Cracking?

Bathroom 1 bathtub crack

Bathtub materials vary in terms of durability. Bathtubs constructed of cast iron, copper, stone resins, or even wood will retain their form regardless of the conditions they are subjected to. After some years of use, fiberglass and acrylic bathtubs will flex marginally due to wear and tear and other factors.

Bathtub fractures are one of the most typical issues that affect fiberglass and acrylic bathtubs. Since these bathtubs are porous meaning, they absorb water over time, and they are even more prone to cracks.

Let us look at the main reasons why your bathtub is cracking.

Dropping Heavy Objects

Dropping a large bottle of shampoo or an electric shaver once may not crack the bathtub; however, repeatedly slamming items in your bathtub will result in cracks.

In some cases, you may only see small divots or dents left behind by falling items; however, over time, these dents and divots diminish the integrity of the bathtub, and small cracks will start to appear.

Inadequate Support

A bathtub must be placed on a firm, flat surface. Weight/force distribution will be uneven if a bathtub is put in an uneven position, causing some areas of the tub to have more weight than others. For example, fiberglass is quite flexible and bends considerably when a lot of weight is placed on it.

As the weight increases, the bathtub will begin to show cracks along its path as a result of strain.

If this is the case, repairing the floor support is the best and long-term solution; otherwise, the bathtub will crack again.

Harsh Cleaning Materials

Many homeowners prefer to clean the tub surface with a strong clarifying solution containing bleach to prevent mold/mildew from building up. This may be counterproductive as abrasive bathtub cleaners such as bleach or any other acid-based cleaner will ultimately wear down the finish on your tub surface.

This, over time, will cause the tub body to absorb water resulting in the bathtub weakening and producing cracks. Fiberglass bathtubs are especially susceptible to this particular problem.

Common Types Of Cracks In Bathtubs

Typically there are 2 types of cracks that appear in bathtubs. 

Hairline Cracks

These are tiny fractures that usually appear after repeated misuse. Whether the reason is abrasive cleaners or your child consistently dropping their toys in the bathtub, this will affect the integrity, and sure enough, cracks will start to appear.

Fortunately, you can seal these cracks and stop them from spreading using repair kits that are readily available. It is, however, advisable to seal these cracks sooner rather than later if not, these cracks not only get larger but, as we mentioned before, will affect the integrity of the bathtub.

Stress Cracks

Stress cracks appear when something heavy impacts the bathtub. Accidentally dropping a large shampoo bottle or a glass jar with your favorite cream will surely crack your bathtub.

These types of cracks can be repaired, too, using a repair kit.

How Much Will It Cost To Fix My Bathtub?

This will, of course, depend on the extent of the damage. A repair kit from your local hardware store will cost you approx $20-$30. A DIY job will involve buying the repair kit and your time and can cost anywhere between $30-$200.

Please note these types of repair kits will leave behind patches in your bathtub and may not be as long-lasting as you would expect.

Alternatively, you can get a professional to come in and do the repairs, which will not only look much better but will extend the life of your bathtub. Naturally, a plumber will be more expensive, costing around $80-$150 an hour, depending on their skill level, but this will still be a lot cheaper than replacing the bathtub altogether.

Step By Step Guide On How To Fix Cracks In A Bathtub

bathtub crack

There are 2 ways to fix the cracks in your bathtub. The first type of repair kit available is a surface repair kit, available as a polymer paint or tape that will only cover the crack on the outer layer of the bathtub, which is basically the same as putting a bandage over the crack and hoping for the best.

This method is a short-term solution. The other and longer-lasting solution is to use an internal repair kit. These kits generally contain glue or a paste that seals the cracks from the inside.

Both are relatively low-cost, between $20 and $40 each, making them a cost-effective alternative to hiring an expert.

Below are the steps using the internal repair kit.

  1. Stop The Crack From Expanding – Drilling a 1/4″ hole at the end of each crack will prevent the crack from expanding further.
  1. Filling The Crack – Follow the instructions of the internal filler and fill in the cracks and the drill holes you created and leave them to dry.
  1. Sanding – Once the filler is completely dry, use light sandpaper of 320 to 400 grit and rub the surface until it is smooth. You can use a small flat object like a piece of wood to ensure a smooth flat finish.
  1. Painting – Make sure to buy the same color spray as your bathtub. Wipe the surface with denatured alcohol to remove any excess on the bathtub surface. Hold the spray can 8-10 inches away and spray a light coat on the treated surface area, and then wait for it to dry before adding more coats.
  1. Polish The Area – Once the painted area is completely dry, you will need a harder finish for that perfect look. You can achieve this by using an auto-polish urethane compound. Clean the surface again with the alcohol and make sure there are no bumps. Apply the polish and wait to dry.

How to Maintain Your Bathtub

WOODBRIDGE BTA1514-C-Drain &O Bathtub, Chrome

Install your bathtub with the necessary support in place so that it does not bend or strain the material.

Check for any leaks regularly and fix them as soon as possible to prevent further damage.

Use bath mats or rugs in front of and behind the bathtub to absorb impact and protect the bathtub surface from scratches and dents that can turn into cracks.

Be careful when using any harsh chemicals or cleaners on the bathtub surface. White vinegar and baking soda are great natural cleaners that are not only non-abrasive but are chemical-free and will not harm your bathtub surface. Always remember to use a soft cloth when cleaning the bathtub.

Dropping heavy objects will inevitably damage the bathtub, so try and avoid that together or as we mentioned before, get rubber bath mats for the interior of the bathtub to absorb any heavy impacts.

Children’s toys usually are the number one cause of scratches and dents in bathtubs. If your child is going to play with toys in the bathtub, then maybe buying some rubber or bath-friendly toys may be an option.


What is the best bathtub cleaner?

There are numerous cleaners available. However, we recommend using vinegar and baking soda. Mix and apply and leave to sit for an hour. Scrub using a non-abrasive sponge and rinse.

How do I know if my bathtub is fiberglass or acrylic?

Acrylic tubs are generally available in more colors, and the edges of the tub are usually thinner. Fiberglass tubs do not have as smooth of a finish as their acrylic counterparts and are cooler to the touch.

Can bleach damage a bathtub?

Absolutely bleach can damage your bathtub. It is not recommended to use bleach in your bathtub as it will corrode the surface.

How long will an acrylic bathtub last?

Acrylic bathtubs last 10-15 years but that can be extended if you maintain them.

Can you take a bath right after cleaning the tub?

It really depends on what you are using. If you are using chemical-based cleaners, then it is better to vent the bathroom first; however, if you clean your bathtub with vinegar and baking soda, then you are good to go.

Do fiberglass bathtubs turn yellow?

Unfortunately, hard water and soap scum will leave your fiberglass bathtub looking yellow. This is especially true if you are using bleach-based cleaners. Using hydrogen peroxide with cream of tartar will easily renew your bathtub and have it look white again.

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