Are Fiberglass Pools Better Than Gunite Pools?
Are fiberglass pools better than gunite pools? First, I need to qualify something that pool owners can tend to get confused about - gunite, gunnite, shotcrete, cast, plaster and tile are ALL concrete pools. So you might be asking a slightly different question depending on the nomenclature you are most familiar with, but the real question that we are asking, and that I am going to answer definitively for you, is whether fiberglass pools are better than concrete pools.
The answer, is no, fiberglass pools are definitively not better than concrete pools. Further to this, this is not a point up for discussion. Fiberglass pools are inferior to concrete pools in every way that a swimming pool could be inferior, except for one thing. Fiberglass pools are both fast and easy. Nobody could argue this point. They simply are faster than other pools to build, and require less overall technical experience and skill. This is just the reality of the situation. In regards to claims that you have heard saying fiberglass pools are superior, these claims are being made by someone selling you a fiberglass pool. I am not selling you a concrete pool, or any pool for that matter, I am just providing some context as a seasoned swimming pool industry specialist in that concrete pools are unsurpassed in design flexibility, strength, reliability, engineering, longevity...other than claiming that the interior suface will last forever, which it won't, I really fail to see how people believe that a fiberglass pool would or could ever surpass the unlimited potential of concrete.
I can hear the "jimmies" gettin' all rustled up from here...good, let the hate flow through you...
Important note on fiberglass pools - At this point I need to take a step back and explain that I have absolutely no problem with fiberglass pools. You have one and love it? That is fantastic news, I am so happy for you! Or maybe you install fiberglass pools and right now you feel invalidated because of some of the things I just said (and am about to say), but you really should not. I did not say that fiberglass pools are bad, or that people should not own them. I am answering a technical question that is being asked, and up until now, is being answered patently incorrectly by fiberglass pools sales people. Fiberglass pools are great and if you want to own one then you definitely should. However, fiberglass pools are inferior to concrete pools. If that matters to you, then you need to be aware of that. Vinyl liner pools are also inferior to concrete pools.
Recently in a very busy Facebook group a home owner asked whether fiberglass pools were better than concrete pools. They seemed genuinely surprised as one by one the comments came in confirming that concrete pools are, in fact, superior. They said this was contrary to every piece of information they had been able to find on the internet - dozens of articles all showing fiberglass pools being the obvious choice for new pool installations. That is why I decided to write this article.
To address the real culprit of misinformation here, concrete pools are not a marketable product in the same way that fiberglass pools are. This makes a fiberglass pool a "product" you can buy, where a concrete pool is an intangible mash of construction skill meets artistic vision. The end result is that very large companies become involved with manufacturing, and promoting, of fiberglass pools. They are huge manufacturing sized companies with deep pockets for advertising. This is where all the press about fiberglass pools comes from. They buy ad space in magazines, do big trade shows with huge eye catching fiberglass pools sitting on display. Concrete pool builders do not do this. Concrete pools are not a product and there are no large, country wide manufacturers of concrete pools with deep pockets to buy ad space, run trade show booths etc. Fiberglass pools are marketed aggressively by big companies as being a better choice than concrete pools. Concrete pools are not marketed at all except for the known convention, if you have enough money you can buy a concrete pool.
Credibility and objectivity - I am a retired pool builder. I have installed every kind of pool that you can install, with my own two hands (not subcontracting out the stages), and there is not even close to a doubt in my mind that concrete pools are the best. Concrete is the single most widely utilized construction medium on the planet. It is not by accident that the entire world over has agreed that when you need to build something, and you want it to last, you use concrete. Let's look at some typical important construction projects that were built from concrete, not fiberglass:
The sarcophagus covering the Chernobyl reactor
Sidewalks, roads, heaviest trafficked commercial walkways
The 2000 year old Pantheon concrete dome
The hoover dam
The foundation your home is sitting on
Okay, the reality is that I understand that these are bad examples because fiberglass was not a good solution for those projects like it is for swimming pools. I understand your argument. But I don't agree with it. In order to dispute it, here are the most likely reasons why you might be told that fiberglass pools are better than concrete pools:
Claim - Fiberglass is INCREDIBLY strong. It is even stronger than concrete or steel (by weight)
If the weight of the shell of the swimming pool was an important factor then you would have an entirely better argument on your hands when talking about the strength versus weight equation. Often fiberglass pool supporters will say something like, "why are hemets made from fiberglass?" which implies that we protect our most important things, ourselves, using fiberglass. Firstly hemets, by and large, are not made from fiberglass. They are made from closed cell foam, carbon fiber and many other forms of adhesive, metal components etc. To call them fiberglass would not be entirely accurate. More importantly, wearing a cinder block on your head would be less than practical. This example falls squarely under "Strong for its weight", which again, is not a factor or measure of final quality in any way for a swimming pool.
Claim - Fiberglass pools never need to be resurfaced, unlike expensive concrete pools which require regular upkeep
First, it is true, that concrete pools will require regular maintenance and repairs. Also it is true that when it comes time to renovate a concrete pool you will end up spending quite a bit of money hiring a local expert to do this work as renovating concrete pools requires specialized skills, experience and equipment. The thing is that fiberglass pools will ALSO need renovations. And those renovations will ALSO be expensive and not something you can really do on your own. The only difference is that the person who built your concrete pool can probably retile and plaster the pool for you again when the time comes. The person who installed your fiberglass pool most likely does not offer gelcoating services or structural crack repair services even though they install these pools for a living. Fiberglass pools also fail, and fiberglass pools also require resurfacing. This, right here, is one of the ways that you are being lied to when trying to compare concrete pools to fiberglass pools. Flat out lied to. Fiberglass pools are not maintenance free, and they do require periodic expensive repairs and renovations.
Ask your fiberglass pool salesperson what happens if the chemistry is very poorly out of balance for a very long period of time. Would that, or could that, result in delamination, gel coat failures, rough crystal like formations over the entire surface, as well as staining from things like cobalt (less a problem with newer generation fiberglass pools). Here is the BOTTOM LINE. Will your fiberglass pool come with a written guarantee that it will NEVER require gelcoat, surface or structural repairs, and if it does these repairs will be 100% covered by the manufacturer. If you can find a fiberglass pool installer willing to stand behind their guarantees of the gelcoat "never" needing to be reconditioned, on paper, then I will be more impressed. Gelcoats can fail on fiberglass pools...it will just be "your fault" when it happens to your pool and that is why it will not be covered under any type of warranty coverage.
Claim - Fiberglass pools are stronger because they are all one piece construction
If you had a fiberglass pool, 20x40' rectangle, and you also had a concrete pool of the same dimensions, and then you picked up each pool and held it up in the air which pool could hold more weight before it sagged, twisted, cracked or folded in half? To actually answer this question you would need to quantify the thickness of the concrete, the type, size and spacing of the reinforcing steel grid, as well as the compressive strength of the concrete mix used. You would also then need to know the grade and thickness of the fiberglass in question. At the end of the day I would put my money on concrete to be stronger when compared like this, even accounting for the fact that the concrete will also need to support its own weight in addition to whatever you added to it. This is specifically why concrete is so widely used in construction around the world...but this does introduce an important concept that fiberglass pool supporters are probably yelling at their screen right about now.
One of the main advantages of fiberglass versus a stronger, albeit more rigid product like concrete, is the ability for fiberglass to absorb stresses. Concrete has an incredibly high compressive strength, but a relatively low ability to absorb force from tension. This is why steel is embedded into the concrete, because steel has a very high tensile strength (and a relatively low compressive strength), opposite to the strength characteristics of concrete. A fiberglass pool does not have a similar system to resist forces, more so a fiberglass pool has a limited ability to flex and twist to transfer the forces as opposed to brute strength to just absorb them like a concrete pool. Thus this aspect of the nature of fiberglass pools is sighted as an advantage over concrete pools, and to a certain degree, it is.
A concrete pool is not supposed to flex, bow or twist. When it does, your shell cracks...and nobody wants a cracked concrete pool shell. If you are currently shopping for a new pool and you are here reading this comparison between concrete and fiberglass pools, you are probably specifically concerned about cracked concrete pool shells. The thing is, fiberglass pool shells can (and do) crack also. When they crack, fiberglass pools are hard to repair, as they are not designed to remain empty in the ground. Concrete pools are not either, but a trained professional can drain and renovate concrete pools without a problem, and usually with minimal effort. A fiberglass pool can be drained by an expert also, but it will take more effort, and there is a higher risk for further cracks, twists or other failures.
Situational Advantages Of Fiberglass Pools
A fiberglass pool, much like a vinyl liner pool, has some unique characteristics that make it situationally an advantage in certain conditions. A concrete pool on the other hand, situationally, can be installed anywhere. It defies logic to me that fiberglass pools are sold against concrete pools on a point for point basis when in reality they are a product limited in design options, without the ability to upgrade aesthetically along with the house and property, which is important when you start looking at half-century long increments of time. When well built, and engineered, concrete is good enough to build a pool, or a bomb shelter, or a skyscraper, or any other structure where reliability of strength is absolutely paramount.
Yes you can get a poorly built concrete pool. But rest assured you could also find yourself buying a poorly installed fiberglass pool as well. This is why doing your research is so important, and using accredited builders is even more so. Just because a fiberglass pool is built in a manufacturing environment does not mean that it ends up in the ground in your backyard without taking some lumps along the way. The lifting, craning and installing of a fiberglass pool can put strain on the shell in weird ways. The shell can also get jostled, bumped or dropped. I watched the next door neighbor to my mother have a pool installed, and the fiberglass shell ended up hitting the chimney and knocking it off the house in a hailstorm of bricks, which in turn decimated the wood deck on the back of the house. The crane ended up not being able to reach the pool hole, and the shell was left sitting, on end, mostly in the hole at the end of the day. I did not return to see them finish up that s#!t show. I saw everything I needed to see. Not that all pools experience this ineptitude, but more to emphasize that being built in a manufacturing environment is great, but it's not like that gigantic pool shell teleports itself into the backyard.
Go with the flow - If your neighborhood has 90% vinyl liner pools, or 90% concrete pools, or 90% fiberglass pools, then you should probably consider getting one as well. Having an obtuse swimming pool is not usually a good thing when it comes time to sell your property one day. Going with the flow for your neighborhood is always a safe bet when it comes to pool installations.
If you find yourself without a clear answer and still considering whether a fiberglass or gunite pool is better, you will need to identify what your priorities are. As identified in this article there are certainly some instances where a fiberglass pool might be the best option for a new installation, but every commercial swimming pool is made from concrete, all the biggest pools in the world are made from concrete, all the oldest pools are made from concrete, all the fanciest and most expensive pools and unique designs are made from concrete...the answer is pretty clear for me, but then again I spent my entire adult life repairing, renovating and building swimming pools, so this is kind of my bread and butter so to speak.
Fiberglass pool installers, I hope we can still be friends. I wrote 244 articles about swimming pools before I wrote this one. I only elected to write this so that pool owners would hear a counter argument to the fiberglass vs gunite debate. I like fiberglass pools. I think they are great. Super easy to install, even if you don't really have any experience installing swimming pools. The gelcoat is very smooth, and instances where chemical imbalance or manufacturing error does not compromise the surface then an impressively long service life can be achieved. But to say that fiberglass pools are better than the most impressively versatile building material on the planet...slow your roll hotshot.
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