Concrete Pools Maintenance Repairs
If you own a concrete swimming pool you are probably excited about owning a top of the line inground swimming pool, but also terrified of unexpected or astronomically expensive repairs. The very essence of concrete pools is their quality, ruggedness and permanent nature so when things go wrong with any one of the integral components that make up your concrete pool...well, it is expensive to fix. There is just no two ways to say it. Add to this that often you can not repair one item without also repairing another. This is how you find yourself scrambling to find funds to cover an unexpected coping, tile and plaster for your pool. But was it really unexpected? Probably not. Let's take a look at some of the symptoms that may have been there but perhaps you did not notice - or if you did notice perhaps you did not fully appreciate the importance of what you were looking at.
As someone who has spent the better part of their adult life building, renovating and repairing concrete pools I can easily say that concrete pools are one of those things where something small can (and most likely will) turn into something much bigger. If you are diligent about watching out for potential problems brewing, and making appropriate maintenance repairs where needed, you can actually reduce the chances of a surprise renovation bill dramatically. For the most part, concrete pools are very predictable and a skilled eye can fairly accurately tell the condition and the approximate time until major renovations will be required for the integral coping, tile and interior surface components. The problem is that most concrete pool owners are not really familiar with how concrete pools tend to fail and will often ignore symptoms or deficiencies which are the only warning you get before things start to get expensive. If you own a concrete pool and you want to avoid being blindsided with sudden repairs then read through this article to see the most common symptoms and maintenance repairs that you should be making to your pool.
Coping, Tile & Plaster
Most concrete pools are built with three integral components which will require periodic maintenance or renovation which are some kind of natural stone or poured concrete coping collar, a tile band at the top of the pool wall, and the interior surface for the pool. These three important parts of a concrete pool work together to create a very water resistant aquatic structure. You notice that I specifically did not say water proof since concrete pools are not water proof. Concrete is a porous building material and even very dense and water resistant mortars like pool plaster will leak (or more accurately leach or wick) water.
There are some concrete products that promote being completely waterproof, as well as additives you can use in concrete mixes to vastly increase the water resistive properties of concrete, but at the end of the day, in one place or another, a concrete pool will be losing enough water from the structure to not be waterproof. So why is this significant? It is important to understand that a concrete pool is not water proof because you need to understand how important it is to be diligent about helping your pool in every way you can to hold water better.
For example, if a brand new smooth finish pool plaster is not water proof...how well do you think rough, pitted and delaminated pool plaster is holding water? Let me tell you, it's not very good. It is the nature of water constantly passing through the concrete of your pool that creates an eroding effect. Cement powder is water soluble and as water passes through cured concrete it can slowly strip away the cement component and leave behind just the aggregates from the original concrete. The more water that passes though the concrete, the more aggressive the rate of decay. This is the reason why you should never ignore a leak in a concrete pool (or any pool) and if you would like to dive deeper into this subject specifically then you might like to read this article about damage from leaks in concrete pools.
Water getting some place it should not be is a concern for concrete pools in more ways than one. Water, either from a leaking pool structure, or from leaking pool plumbing, can also cause the failure of pool decks, coping and tile as well. In fact, keeping your pool in good (and expensive surprise free) condition is almost entirely about controlling where, and where not, water goes in and around your pool.
This is the way in which the coping, the tile band and the interior pool surface work together. All three of these items need to be in perfect functional condition to keep the water "out" from where it should not be on your pool - and a failure of any one of these three components will allow water to begin to damage all three of these components. This makes your goal as the pool owner to prevent a failure from any one of these items, and also to specifically understand how each of the coping, tile and plaster need to be working, and working together, in order to protect your pool as a whole. A failure of any one of these items represents a failure of the system as a whole. If you understand this then you are light years ahead of what most pool owners know about maintenance and repairs on their concrete pool.
Coping Maintenance For Concrete Pools
The coping on a concrete pool is not the same as coping on a vinyl pool. On a vinyl pool, coping is a track that runs around the top perimeter of the pool wall which retains the bead of the hanging liner. On a concrete pool it is totally different. Concrete pool coping is the area of the pool deck that is directly overtop of the vertical pool wall. Usually this will be either natural stone or cast concrete and will include a 1.5" to 3" cantilever over the edge of the pool.
The reason why a concrete pool needs coping is because the pool shell will not move at the same rate as the surrounding deck structure. Any movement such as contraction or expansion, settling, shifting or any other cause could result in something known as "deck shear" IF the pool did not have a coping installed. In fact, many modern designs call for a continuous pour of the pool deck up to and including where the pool coping should be. Designs like this are very likely to experience a deck shear failure where the pool deck moves but the pool shell does not. This places extreme forces on the top of the pool wall and can result in a structural failure anywhere along or near the top edge of the pool wall - right where your tile band is located.
For this reason, a smart design involves a pool coping which is isolated from the remainder of the pool deck via a small gap between the deck and the coping. this joint is then filled with a flexible sealant to marry the two edges together and to create a water proof (resistant) joint between the deck and the coping. It is a failure of this flexible joint in particular that can, and will, lead to early failure of your coping stones as well as potentially the tile band in your pool as well. As a concrete pool owner you should consistently be inspecting this flexible bead for any sign that it is failing and replace it completely at the first sign of something wrong.
When the expansion joint between your pool deck and coping fails this will allow water to access behind the pool wall - both from rain runoff but also splashout. As indicated earlier in this article, any time that water is getting some place it should not be on a concrete pool there is a tiny, incremental erosion effect that begins. This however pales in comparison to the concern of a failed expansion joint in areas where the pool will experience freeze and thaw cycles in the winter.
If water is able to access behind your coping then it can saturate this area, and specifically the joint where the coping is attached to the top of the pool wall. Since most concrete pool coping is mortar set this can result in water delaminating or fracturing your coping when it expands into ice. This, in turn, allows more water into places it should not be and during the next freeze and thaw more incremental damage will happen. When you are inspecting your pool for any of this type of damage, in addition to the expansion joint, you should also check to see if your coping has become delaminated. Delaminated coping is either the cause of, or symptom of, water getting where it should not be - in either case the problem is the same in that this area will deteriorate very quickly and most likely damage the immediate surrounding structure. To check your coping for delamination simply draw something heavy like a hammer slowly over the coping around the perimeter of your pool. If the coping is delaminated anywhere it will be very audibly noticeable as delaminated coping sounds hollow.
Tile Band Maintenance For Concrete Pools
Other than looking pretty what exactly are tiles doing for your pool - if anything? There are some very good reasons that your pool has tiles along the top of the wall. The first is simply that all of the oils and debris in your pool will float along the surface. Imagine a bathtub scum line but on a much grander scale. Tile, at least as traditionally used for pools, is very water resistant - much more so than any concrete or mortar based products. Pool tiles are most often non-porous and facilitate easy removal of scum lines and a hearty resistance to staining. This, however, is only one reason why you need tiles in your pool.
The more important reason that you need tiles in your pool also relates to how tiles can be non porous and can provide enhanced protection against water permeability. The weakest area of a concrete pool structure, by far, is the top of the vertical walls. This is why when you build a concrete pool you would normally install a bond beam. Essentially, a bond beam is an area at the top of the pool wall where the concrete is thicker than the rest of the vertical pool wall, and generally contains a very robust rebar reinforcement of four horizontal bars of rebar wrapped in steel rebar box ties. In the finished product this adds a rim to the top of the pool wall, so to speak, and one that is extra thick concrete with extra steel reinforcement. All of this is meant to counteract the forces acting on the top of the pool wall and add structural stability to the shell. It would be a shame to do all of this extra work to simply have water come along and permeate the structure at the waterline and begin to degrade its strength. For this reason tiles are used along the top of the pool wall to assist with the resistance to water absorbing into, and passing through, what is the weakest area of the pool structure.
So what do you as the pool owner need to know about maintaining the tiles in your pool? First of all, don't delete them in a future renovation. I have seen countless concrete pools where owners elected to delete the tile band (almost exclusively due to remediation costs) and elect to simply parge over that area of the pool with mortar. This would be a mistake that I would certainly not recommend for any concrete pool owners to make. Having a new tile band installed in your pool is expensive but attempting to delete it during a renovation to save some cash will almost certainly end up costing you more in the long run.
The next thing you need to know about tiles in a swimming pool relates, again, to expansion joints. Any time you transition between two differing surfaces which are both rigid, such as where the concrete pool wall meets the underside of the concrete pool coping, you need a flexible expansion joint. For this reason you are not supposed to grout the edge where the top of your pool tiles meet the underside of your pool coping. If you attempt to bridge a transition gap like this between two rigid (and differing) materials with another rigid material (grout) then you will certainly experience a failure of this transition gap. You need to accommodate for any miniscule movement that can happen between these surfaces by providing an expansion joint. If you were to install pool tiles where the tiles are touching tight to the underside of the coping, it is very likely that before long you will find the entire top row of tiles to de cracked, delaminated or fallen off.
Now, if it were not for the water aspect, it would not be a huge deal if you did not have an expansion joint in between your tiles and the underside of the pool coping. However, without a water proof expansion joint, once again water will have the ability to get where it should not be. If the flexible expansion joint is failing or missing from your pool in this area then you will be allowing water to access the joint where your pool wall ends and your coping stones begin. This cold joint between the wall and the coping, even when applied correctly using conventional concrete bonding techniques, can only result in approximately an 80% mechanical bonded versus one continuous pour of material. This means that this is the weak link at the top of the pool wall, which again, is the weakest area of your concrete pool.
You have those tiles there to help you protect that area for water permeability, but without a flexible transition bead water will access the cold joint and wick into the concrete here. Again, in cold climate areas this situation would be most unforgiving as the slow eroding process of the water passing through the concrete will never get to realize its full potential since it will simply not last that long. In areas with freeze and thaw allowing water to access this unprotected cold joint will result in an increased potential for water trapped in the shell behind the tiles to freeze, expand, and pop off some tiles. Additionally the water accessing the cold joint in this location could likely have the same result as water accessing the coping cold joint from the backside as with the failed deck to coping expansion joint - water freezes, expands, and delaminates the coping in that area.
As a concrete pool owner you should inspect the flexible bead on the underside of the pool coping where it meets the tile band and replace this any time that you notice a deficiency here. Similar to checking the coping stones for delamination you can also check tile in the same way.
If you (carefully) draw a hammer over the tiles you will easily be able to hear any areas which have delaminated since they will be very hollow sounding.
Concrete Pool Interior Surface Maintenance
The interior surface of a concrete pool is usually plaster or a similar dense mortar based product with a high degree of resistance to water permeability. This thin layer of dense mortar with a smooth finish is what is supposed to prevent the concrete pool shell from wicking water at an advanced rate. As pool plaster ages the water which is able to permeate the surface will slowly erode the structural integrity of the concrete. The cement component will slowly wash away with the movement of water leaving behind a very rough and sandy feeling surface - and one that has notably less resistance to water than a newer, smooth plaster.
Many concrete pool owners make the mistake of trying to get more service life from their pool surface than they should. The days of asbestos infused pool plaster that lasts 30+ years is gone, thankfully, and modern interior pool surfaces will last between five to ten years on average before they should be remediated. As the plaster becomes rough and more porous over time it will be inclined to stain at which time pool owners often look to an acid wash process to rejuvenate it. The problem with this is that while the acid wash will undoubtedly make the plaster looker cleaner and newer, it actually serves to make the plaster even less water resistant than before. When you acid wash pool plaster you are manually stripping out and burning off cement within the plaster layer. Again, this causes the surface to be even more sandy and even more porous than before. It is estimated that an acid wash can easily take two years off the service life of your plaster - and much more if your acid wash is too strong, as it often is to get the best visual results. A clean and white plaster does not mean it is good. If the plaster is rough and sandy to the touch then the hard trowel smooth finish which had been applied originally has been lost.
As discussed throughout this article when you end up with water where it should not be on a concrete pool this is where you can get into large and unexpected repairs. If every square inch of the entire surface of your pool is leaching water at an advanced rate then this will also put both the attached tile band, as well as the pool shell structure itself in jeopardy. Heavily wicking pool plaster will allow the chlorine in the water to access the rebar reinforcing grid which can start to rust aggressively. Given enough time the weakening steel structure combined with aging and eroding concrete can start to manifest in cracks in the pool. As a concrete pool expert I can say with certainty that if there is anything you for sure want to avoid with your concrete pool, it is structural cracks in your pool shell.
In order to prevent any and all of these potential failures with your concrete pool you need to be sure to keep the water where it should be - inside the pool. Be diligent about inspecting and replacing expansion joint sealant where the coping meets the pool deck, and also where the tile band meets the underside of the coping. When it comes time to do something about the aging interior surface in your pool many pool owners will look towards painting the pool as potentially a lower cost alternative to a new plaster surface...but does this actually save you money? Concrete pool experts like myself tend to disagree. If you would like to learn more about the long term cost comparison of plaster versus paint for the interior surface of concrete pools then check out this article about comparing pool plaster VS paint.
Material Used For Flexible Expansion Joints
So by this stage in this article you are probably getting a really good sense of how important those flexible expansion joints are on your pool. So supposing that you have looked at yours and they are either missing or deteriorating and need to be replaced - so what product are you supposed to use? The most common, and the one that I have found to be the most successful is a urethane based concrete sealer.
I have tried quite a few polyurethane sealers over the years for use on swimming pools and by far the best one that I have found is this NP1 polyurethane caulk. This stuff is very difficult to work with since it is incredibly sticky - but that is also exactly why you want to use a product like this. It is extremely durable and long lasting and bonds very well to concrete surfaces. I have also used this product below the waterline to seal the underside of return pipe wall penetrations to help limit the potential for a leak on the bottom dead center of pipe penetrations.
I am not sure if you can get this product in regular hardware stores. I used to be able to buy it at Home Depot but I have not seen it for sale there in years...perhaps in your area it is available. If not, you can always order it online from Amazon but just be sure to order enough tubes to do the job in one shot. You don't want to come up short with how much you have on hand once you get started. The amount you need will of course depend on the size of your pool the size (width and depth) of your expansion joint, as well as your ability to limit wasting of the product. Be sure to tape off the area you are going to seal as this product is very difficult to remove from every kind of surface - including yourself. Make sure you have a ton or clean rags on hand when you are working with a product like this as well as some backer rod to help fill large expansion joints before applying the urethane bead.
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