3 Ways To Fix Spider Cracks in Fiberglass Pools

Spider cracks or hairline cracks on your fiberglass inground pool can be problematic. But thankfully, they’re rarely a major cause for concern as they typically only affect the gel coat and not the laminate layers of the pool. Because of that, spider cracks can be resolved with several quick fixes.

There are three ways to fix spider cracks in fiberglass pools:

  1. Apply fiberglass paint.
  2. Replace the damaged portion.
  3. Fill cracks with fiberglass epoxy resin.

With frequent use, even durable fiberglass pools may show signs of wear in the form of spider cracks. Luckily, they are typically superficial cracks on the gel coating and don’t affect the fiberglass structure. In this article, we’ll discuss the above repair options in detail so you can do them yourself or learn when to call a professional to fix the cracks properly.

Spider cracks in your pool may be superficial or run deeper

1. Apply Fiberglass Paint

Spider cracks (also called hairline cracks or stress cracks) may occur due to improper handling, poor installation, or stress points on the surface of the glass. They’re called spider cracks because they’re very thin lines that branch out in different directions, much like a spider’s web does.

Most spider cracks are nothing serious, affecting only the gel coat or the outermost layer that protects the fiberglass itself. A telltale sign of a superficial or minor crack is if it’s less than half an inch (1.27 cm) in depth. 

In this case, you can simply apply fiberglass paint to the crack to keep it from spreading. The paint also covers it up, so it doesn’t affect the appearance of your pool. However, it’s often hard to see superficial spider cracks, even in a pool with no water.

Types of Fiberglass Paint

There are different kinds of fiberglass paint to choose from. Your choice depends on the type of application you wish to do, your preferred adherence strength, and the ability of the paint to hold up without blistering. Here are three types of fiberglass paint.

Acrylic Latex

Acrylic latex is a water-based paint that is super easy to apply. So, if you’re looking to do the paint job yourself, this is a good option. 

It also holds up well and is resistant to most cleaning materials; thus, it doesn’t blister or crack easily. And since it dries quickly, it’s great for those looking to get the job done as fast as possible.


Urethane fiberglass paint, unlike acrylic latex, makes use of a chemical solvent and is not water-based. Therefore, it’s not recommended for use in an area without proper ventilation, as it contains harsh chemicals that could harm your health if inhaled. 

Regardless, when painting an outdoor pool, you still should wear a protective mask if you decide to use this type of paint.

But while using urethane may require extra care, it does create an appealing shiny finish that is incredibly durable. And its high resistance to wear makes it a good option for outdoor pools.

Combination of Acrylic and Urethane

If you want the best of the two previous types of paint, you may opt for a combination of acrylic and urethane. This combo provides strong adhesion. So strong that it can easily bond to fiberglass even if you don’t clean or sand it beforehand.

Using this type of paint will not only save you time, but it will also make your pool highly resistant to wear.

Nonetheless, should you notice any deep or large cracks in your fiberglass pool, it’s best to get help from a professional and either fill the cracks or replace the damaged portion of the pool. We’ll discuss more on this next.

2. Replace the Damaged Portion

If the cracks are half an inch (1.27 cm) or more in-depth, and you see them causing structural damage to the fiberglass, you’ll need to replace the damaged portion. Again, this is not something you want to attempt to do on your own unless you are a professional.

Causes of Structural Damage in Fiberglass Pools

It’s important to know what’s causing structural damage in fiberglass pools so that you can prevent them in the future. If you already see signs of structural damage, it’s best to call a professional right away to keep the cracks from affecting a larger area.

Here are some of the most common reasons why fiberglass pools crack and how you can avoid them.

Improper Installation

Getting a contractor who knows what he’s doing is important because a poor installation will cost you lots of money in repairs later on. In the case of fiberglass pools, the most common problem is that some contractors do a poor job of leveling the pool, creating pressure points that lead to cracks.

Poor manufacturing quality

Sometimes, it’s not the contractor but the manufacturers that cause the problem. Some manufacturers make the fiberglass layers too thin, making them prone to breaking. 

If you have an expert contractor, though, he’ll most likely be able to tell good-quality fiberglass from bad-quality ones. That’s why getting a good contractor is really important.

Manufacturing errors may be the cause behind spider cracks.

External factors

An outdoor pool is more prone to external factors that may cause damage, such as falling tree branches. With enough pressure, these objects can put stress on the glass and cause it to crack.

3. Fill Cracks With Fiberglass Epoxy Resin

Another way to repair spider cracks on fiberglass pools is by filling in the cracks with epoxy resin. This is a meticulous process, however, so you may need to contact a professional to do it for you. Also, epoxy resin is a harsh chemical and shouldn’t be applied using bare hands or without a protective mask on.

Moreover, since epoxy resin will not bond well with a gel coating, using it on superficial cracks on the gel coating will only be a temporary fix. If you decide to use epoxy resin, it’s best to sand the fiberglass to remove the gel coating first, then apply it to cracks on the fiberglass. 

However, while epoxy resin bonds well with fiberglass, if you see significant damage, you should opt to replace the damaged portion altogether.