Considering one’s preferences and economical resources, a concrete swimming pool has some advantages over other types of pools. With its size and shape limited only by imagination, budget and yard size – and its average useful life of 50 years – a concrete pool is literally a solid recreational and aesthetic amenity for your home.
But what if you’re noticing cracks in the plaster finish of your pool? Does this mean your pool is leaking? Is it time to call a pool repair contractor? That depends. Knowing what to look for can either help put your mind at ease, or raise a red flag to schedule an urgent appointment with that professional contractor!
Not All Cracks Mean Trouble – Surface Cracks are Common
Swimming pool cracks are often on the surface of the pool body in the plaster coat, and do not run all the way through the pool body itself. As BuyersAsk explains it:
“Not all pool cracks mean that the pool is leaking, i.e shrinkage cracks are normal; they are shallow and just part of the curing process that occurs when the pool is first shot with gunite or shotcrete. The majority of in-ground pools are constructed of 6 to 8 inches of gunite or shotcrete, a concrete type of material, spayed over rebar steel reinforcement.
“The top edge of a concrete pool body usually has an extra wide area (about 12 inches) of gunite or shotcrete that adds more strength to the top rim of the pool shell; this top area is called a bond beam. Overall, in-ground concrete pools are usually very strong and last for many years, especially with proper maintenance.”
Common causes of surface plaster cracks include the following:
Shrinking pool plaster – Craze cracks are small clustered cracks that occur when the pool plaster shrinks. As Marcus Sheridan – owner of River Pools – says, “Plaster tends to shrink as water in the plaster mix gets absorbed during the curing process, but if there is too much shrinking, craze cracks can appear. Pool plaster crazing is a pretty common problem, and the consequences are usually minor. When the crazing is too bad, however, it can cause staining, algae issues, and calcium nodules. A bad case of crazing will require you to replaster your swimming pool.”
Shrinking concrete – According to BuyersAsk, it’s very common for concrete to experience shrinkage cracks when it is first placed. “Excessive temperatures, improper curing, wind or excess water in the concrete mix can also contribute to shrinkage cracking. These types of cracks are generally small, shallow, in random locations and do not result in leaking.”
Shifting soil beneath the pool – Thin hairline or eggshell cracks close to the plaster surface may be caused by shifting ground. Although such cracks are usually only cosmetic versus structural, they’re a concern, as they can serve as harbors for algae to take hold. Once established in this way, algae can be hard to remove using pool chemicals alone. In addition, too much ground movement under and around the swimming pool may eventually cause structural cracks.
Damage from objects thrown in the pool – When a hurricane warning is issued, still too many people try to protect their patio furniture (and prevent it from becoming projectiles) by putting it into the pool. Doing so can damage your pool’s finish and cause staining. Instead, tie the items down to keep them from blowing into the pool, around your yard, or through your windows!
Prolonged imbalanced water chemistry – According to Blue Haven Pools & Spas, cracks can occur when water chemistry becomes disrupted because of having to add a large amount of water to the pool due to evaporation. Rain is also a cause. When water from afternoon thunderstorms (or hurricanes) dumps into a pool, the levels of pH, free chlorine and total alkalinity take a big hit. This creates an unfavorable environment for pool plaster that can lead to numerous problems if not corrected.
In such a situation, shocking your pool after heavy rains is recommended. Our blog post – “The Shocking Truth About Shocking Your Pool” – covers this topic in detail. Rain water can bring with it dust, air pollutants, algae spores and pollen that can disturb your pool water chemistry, consume your chlorine and discolor your water. Also, heavy storms bring with them parts of overhanging trees and overflowing planters – as well as soil from the adjoining lawn laden with bacteria, phosphates and other debris.
While practicing good pool maintenance can help stave off some types of surface cracks, plaster will eventually age and show signs of degradation – which is normal. Depending on a variety of factors and your pool water treatment routine, the typical lifespan of traditional marcite plaster is 7 to 10 years. If the finish includes a quartz aggregate blend, the time table should extend another five years.
Although plaster cracks rarely progress into the pool’s concrete shell, they do need to be repaired to maintain the integrity of the pool finish as well as to prevent algae from gaining a foothold. So while it’s not an emergency, this should be done sooner rather than later.
Structural Cracks are Cause for Concern – How to Identify Them
Structural cracks occur in the shell of the pool and may appear in various locations as vertical or horizontal cracks on the sides or bottom of the pool. The majority of structural cracks running through the concrete (gunite or shotcrete) will also be mirrored through the plaster coating or the tile area over the bond beam. Cracks in a pool that’s significantly out of level are an indication of a serious problem.
The presence of structural cracks may mean that your pool is already leaking. Our blog post – “How Can I Tell if My Concrete Pool Has a Leak?” – lists the following signs of a pool leak:
- Cracks in the concrete vessel.
- Loose or displaced tiles.
- Settling of the concrete vessel into the ground.
- Wet spots or standing water around the pool.
- Adding more than usual water to your pool.
- An increased water and electricity bill.
- Algae formation, especially after a chemical treatment.
- The automatic filler releases water constantly.
Types and Causes of Structural Cracks
As you might expect, the causes of structural cracks are more fundamental than surface cracks. Some of the most common include the following, provided courtesy of BuyersAsk:
Faulty design and engineering – If a pool is not properly designed and engineered, the likelihood of the shell to crack increases. Often, the first flaw of engineering a pool is failure to test the soils and engineer the pool based on the soil load bearing capacity and stability. Moreover, poor design of the areas around the pool can contribute to structural cracks – for example, improperly planned and constructed retaining walls and the concrete deck area around the pool.
Poor workmanship – Failure to follow the construction plans when building the pool – or taking shortcuts – is another cause of structural cracks. Adding too much water to the gunite or shotcrete when spraying it on the rebar or failure to adequately tie the rebar in place when placing the rebar may cause cracks. Even not keeping the pool sufficiently moist after the concrete is sprayed on – especially on hot days – will cause cracking.
Soil issues – If the pool contractor left uncompacted soil when digging the pool hole and then built the pool on this poorly compacted soil, cracking could result.
Bond beam cracking – This type is one of the most common cracks that develop horizontally at the bond beam or waterline tile area. It is an area where the tile circles the pool at the waterline level. A pool with a concrete walk or deck area must have an expansion joint between the concrete deck and pool. But if there is no expansion joint or no place for movement, a crack can occur. A concrete deck can expand due to soil movement or wide variation in temperature, causing expansion and contraction, resulting in cracks. Besides noticing the cracks, missing/cracked tile and cracked, loose, or damaged coping are other signs that indicate this problem.
Rebound cracking – Rebound refers to the material that bounces or flies off the rebar and existing concrete. Rebound material is weaker than the original material because it has a higher concentration of sand and less cement. Contractors reuse it on the bottom of the pool, the seating benches in the pool below the pool, or in the step entry areas to save labor and material. Using rebound material for construction is poor workmanship and can result in weakened areas or cracks. They often occur at the entry step area. Typically, they don’t go deep into the shell, and may not cause a leak.
Mirrored or reflective cracking – Tile and plaster often mirrors a crack that is behind them. For example, if there is a crack in the bond beam, the tile may crack in the same area that the bond beam is cracked. The same is true with cracks in the plaster. Cracks may also appear in areas where the concrete covering the rebar or piping is insufficient. When the rebar has insufficient cover, then there may be a pattern of cracks that reflects the rebar pattern. Over time rust may come out of these cracks and that can be a significant concern, as the rebar rust expands in volume up to four times its diameter. This expansion creates tremendous pressure on the concrete, causing spalling, cracks and damage.
The Take-Home Message
You don’t need to panic over every crack you notice in your concrete pool, but you do need to take immediate action if a crack shows indications of having a structural cause. Should this be the case, your pool is also most likely leaking. If you suspect a crack is more than skin deep, call us! Certified Leak Detection uses technology and techniques we have developed over 20 years in business. In addition to quick detection of pool leaks, we provide industry-leading leak detection for spas and hot tubs, as well as fountains. Serving areas throughout Central Florida – including Orlando, Longwood, Lake Mary, Sanford, Kissimmee, Clermont and Winter Springs – our team is ready to answer your call. Contact us for quick, reliable service!