Pool Plaster Delamination: What It Is and How to Address It

Written by Michael Dean
July 5, 2023

pool plaster delamination and question mark

Every swimming pool owner knows the work and effort that goes into maintaining a pool. Every aspect of the pool needs to be taken care of, and everything comes with its own range of issues. When it comes to pool plaster, one issue you may come across is delamination.  If you’re unfamiliar with this term, this article is for you!

In this article, I will explain what pool plaster delamination is, what the causes are, how to fix it, and how to prevent it.

Main Takeaways

  • Delamination occurs when there is a bond failure between the plaster and the concrete underneath, creating an air or calcium cavity to form.
  • Pool plaster delamination can be fixed by using epoxy putty or by replastering the entire pool, depending on the extent of the damage.
  • Having your pool properly plastered the first time is the best way to prevent delamination of the pool plaster.
  • Repairing delamination costs around $20, whereas replastering the pool costs around $7,000 per 1,000 square feet.

What Is Pool Plaster Delamination?

Simply put, pool plaster delamination is a bond failure between the concrete or gunite and the pool plaster. This separation allows air to fill the cavity, resulting in bumps and bubbles forming on the pool plaster’s surface. These small air-filled cavities are also called calcium nodules.

pool plaster delamination

While pool plaster delamination usually occurs in smaller areas, they can even take up an entire side of the pool if they are left to grow. If left untreated, they grow bigger and begin to crack open, where algae and other bacteria can grow inside the concrete or gunite of the pool structure.

What Causes Delamination?

One of the leading causes of pool plaster delamination is the bond failure between the pool plaster and the concrete/gunite underneath. This can occur because the bond coat wasn’t thick enough or wasn’t applied properly – a big issue and a sign of a bad plaster job. Delamination can also happen if the pool plaster was left exposed for too long before being refilled. Generally, it is a bad plaster job that leads to delamination.

Sometimes, the pool structure can shrink and expand, known as structural flexing, causing small hairline fractures to form in the pool plaster. Environmental factors like humidity and sun exposure can also create structural fractures, so if you live in a hot, humid area, you need to check for any cracks on your pool’s surface as part of your regular maintenance routine.

While these cracks are minute, they can grow just enough to let in a small amount of water beneath the layer of pool plaster. Once underneath the pool plaster, the water dissolves into calcium hydroxide. This calcium hydroxide hardens into those lumps and bumps you see on the surface of the pool plaster.

How To Fix Pool Plaster Delamination

There are two ways to go about fixing pool plaster delamination. 

If a small section of the pool is affected by delamination, you can do a quick repair job without having to drain the entire pool. You can do this using underwater epoxy putty or underwater pool plaster. The area around the nodules and bumps will have to be removed using a paint chipper; the entire area where the delamination occurs must be exposed.

Once the area has been chipped away, you can begin pressing the putty or plaster into the affected area, ensuring it is smooth on the surface and around the edges. This type of fix is super easy and quick to do.

This underwater repair job is only suitable for small areas of delamination. If the delamination in your pool affects a larger area of your pool, you will need to replaster the entire pool.

If the entire pool needs to be replastered, it is best to leave this to a professional, as they will need to remove all the old plaster off the pool surface. The entire pool plaster process can be complicated and hard work, not to mention expensive!

How To Avoid Pool Plaster Delamination

Unfortunately, pool plaster delamination can occur soon after having the pool replastered, or it can suddenly spring up ten years later. The only way you can try to prevent delamination is by having your pool plastered correctly the first time. Therefore, you should foot the bill and pay to get your pool plastered by a professional. This should not be a DIY project unless you know what you are doing.

Another way to prevent delamination is to care for your new plaster properly. In particular, the first two weeks after your pool has been plastered and the water refilled is crucial. During those two weeks, you should scrub and brush your pool walls at least twice a day and slowly adjust the chemical levels in the pool. Properly caring for your new pool plaster will go a long way in ensuring that the plaster cures as best as it can.

Pay attention to the surface walls of your pool, and regularly check for any lumps and bumps on the pool plaster. Also, check for any hairline cracks or lines, as the earlier you can patch them up, the lower the chances of delamination occurring. And if it does, you can at least prevent it from growing and spreading elsewhere in the pool.

A final way to prevent delamination in your pool plaster is to make sure that the company or professional you have hired to plaster your pool has good reviews and knows what they are doing. I can’t stress this enough: avoiding poor pool plastering is the best way to prevent delamination. 

Costs To Fix Delamination vs. Replastering

If the problem area is small enough, you can get away with simply repairing the area where delamination has occurred. You do not even need to empty the pool water for this. Either purchase some epoxy putty or underwater pool plaster to fix small areas of delamination. This will generally cost somewhere between $10 to $90.

Replastering your pool will be a lot more expensive as the pool will need to be drained, and that alone will cost anywhere between $70 and $150 if you use a professional service. The cost of replastering a pool will vary depending on pool size and what plaster and finish you have chosen, but the average price of pool plaster is around $7,000 per 1,000 square feet. And yet still, you will need to consider the cost of refilling the pool once it’s been replastered.

Other Common Plaster Issues

Aside from pool plaster delamination, there are a few other plaster problems that may arise over your pool plaster’s lifetime.


Mottling is the gray discoloration of the pool plaster, usually caused by external forces like extreme heat and sunlight, wind, high humidity levels, and water temperatures. Unfortunately, you can’t avoid mottling, but the good news is that it won’t impact the durability of the plaster itself. Instead, it is more of an aesthetic issue. An acid wash may get rid of mottling in some cases.


Etching in the pool plaster is the lumps, dents, and lines that form on the surface. These bumps and lumps make the plaster exceptionally rough on swimmers’ feet.  This issue is caused by poorly balanced pool water. Low pH levels and unbalanced calcium and alkalinity levels in the pool can cause this issue. To prevent this problem, always test the chemical levels of the pool water.

Pool Plaster Dust

Pool plaster dust can also wreak havoc with your pool plaster because plaster dust is made up of dissolved calcium, which can cause problems with the chemistry of the pool water. Excess pool plaster dust could also be a sign of calcium loss in the pool plaster, resulting in a more porous pool plaster that might not last as long as it should. 

More questions? Let me know; I’m happy to help!

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