Concrete Pool Shell Failures - How To Avoid Cracks
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Cracks in a new concrete pool is just about the last thing you want to see when you are having a new pool installed. This video talks in depth about concrete swimming pools (both new and older, existing ones) and how concrete pools tend to break. Why do some concrete pools crack and others do not? The answer is most commonly that the two pools are built differently. How thick the concrete is, the compressive strength of the concrete used, the amount (and size) of the steel reinforcing used all will matter. Further to this there is also the ground preparation and material type as differences of deficiencies here could easily expose a concrete pool shell to extreme forces that cause it to crack.
When it comes to evaluating cracked concrete pool shells and looking at the viability of fixing them you have to be extremely careful to not throw good money after the bad. If the pool shell has been built with inferior materials or technical process then no amount of repair work is going to make up for this. You could spend tens of thousands of dollars fixing a cracked concrete pool only to have it immediately crack again upon filling, or fail within an unacceptably short period of time. Ground prep, concrete thickness and compressive strength as well as the reinforcing steel specifications are needed before you can even think about repairing a cracked concrete shell. Maybe you can flash 4" more of concrete over the walls / floors. Maybe you can build a smaller pool inside of your existing pool. Maybe even you could repair the crack and the pool will hold now that it has finished moving or sinking...but you really can not know if the pool is viable without doing coring and X-rays to determine strength, thickness and steel reinforcing within the concrete.
Soil Movement / Settlement â When the ground under the pool shifts, the concrete shell moves with it⌠until it doesnât. Concrete canât flex much, so any settling, voids, or unstable fill material under the pool often leads to structural cracks. This is especially common when builders backfill improperly or when pools are built on uncompacted or expansive soils.
Expansive Clay Soil â Clay expands massively when wet and shrinks when dry. If your pool is sitting in expansive clay and there arenât proper soil engineering and drainage measures in place, the pressure cycles can literally push and pull the pool shell apart over time. Pools in these areas need special engineeringâmany older ones didnât get it.
Hydrostatic Pressure â Groundwater pushes upward and sideways on the shell. If that pressure exceeds what the structure can resistâespecially during drainingâthe pool can crack or even float. Hydrostatic relief valves can help, but if they fail or were never installed, groundwater becomes a silent destroyer.
Poor Steel Reinforcement (Rebar) Layout â Concrete needs steel to give it tensile strength. If the rebar spacing is too wide, too shallow, missing entirely, or installed incorrectly, the shell becomes weak and cracks much more easily. Youâd be shocked how many âbudget buildsâ cut corners on steel.
Thin or Weak Shotcrete/Gunite Application â If the shell wasnât shot thick enough, or if rebound material was improperly used in the walls or floor, youâre basically swimming in a concrete eggshell. Poorly applied shotcrete can delaminate, develop structural cracks, or fail under normal soil and water pressure.
FreezeâThaw Damage â In cold climates, water gets into small cracks or porous areas, freezes, expands, and forces the cracks wider. Over many cycles, this can cause major structural damage. Proper plaster maintenance and sealing helps keep this from happening.
Tree Roots â Large trees near pools are more than landscapingâtheyâre hydraulic jacks. Roots can apply massive lateral pressure, enough to crack decks, patios, and eventually the pool shell itself. Even if roots donât crack the shell directly, they can shift soil around it, leading to cracking over time.
Plumbing Leaks Beneath the Pool â If an underground pipe leaks, the escaping water washes away soil and creates voids under or beside the shell. Once the shell loses uniform support, it eventually cracks under its own weight. This is one of the most common causes of unexplained cracks.
Improper Draining or Empty Pool Conditions â An empty concrete pool is far more vulnerable than a full one. Without the internal water weight, high groundwater or expansive soil can push or deform the shell, causing cracks. This is why draining a pool without professional evaluation is a dangerous move.
Age and Material Fatigue â Even well-built pools break down over decades. The concrete, rebar, and surrounding soils change over time. Tiny stress cracks can develop into larger structural cracks simply because materials age and the environment keeps applying force.
If you have questions about a cracked concrete pool shell you can always Ask Steve directly for help. Whether you just have a question or plan a full scale renovation or repair Steve can help you better understand your options.
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