A relaxing day by the pool can be quickly disrupted by an unsightly trip hazard. When you notice your concrete pool deck is no longer level, it’s a clear sign of a problem. This pool deck shift isn’t just an eyesore; it can damage your largest home upgrade and create a real safety risk. We often get asked why concrete around the pool moves. While there are several potential causes, we find it usually boils down to one of three common reasons. Understanding them is the first step to protecting your investment.
1: Un-compacted Backfill of Soil
When a pool is installed, the dug hole is typically made 3-5 ft larger than the pool itself. This is done to provide access for the plumbing and structural elements of the pool. Once this is complete, the installers will backfill using the leftover soil and lightly tamp the dirt for compaction so as not to disrupt the soil. When the pool is installed, there is no water to counteract the soil’s weight, so the installers try their best not to over-compact the dirt so they do not damage the pool walls, plumbing, etc. Over time, this soil naturally will compact more with the changing seasons. Then, the concrete on top of that soil will shift and move, leaving uneven concrete.
2: Washing out underneath the concrete
Most commonly, the soil under the was placed over backfilled soil. That soil is much more prone to absorbing or allowing pass-through rain water. This is because it is less dense than the undisturbed soil neighboring it. Water intrusion slowly washes out voids under the concrete coping and decks that slowly allow the concrete to settle. This can also be seen when leaks in the plumbing lines connect to your pool’s pump. Irrigation lines, undirected downspouts, and patio runoff all contribute to the issue of soil washing out under your pool’s concrete surfaces.
3: Extreme Drought
When we experience seasons of little to no rain, the clay soils around our pools begin to lose their density. Naturally, the soil starts to shrink in size because of the lack of moisture. When the soil shrinks, it creates voids under the concrete that cause the concrete to shift over time. Because the soil immediately around the pool is backfilled soil, it is common to see more shrinkage in that soil than the dense virgin soil that may be found in your yard that has never been disturbed by heavy equipment. Subsequently, the large cracks left in the soil from shrinkage leave paths for water when the rains return, and then washout increases the likeliness of settling concrete.
With these most common causes, there are ways to prevent them from occurring. Maintaining proper drainage away from the area and addressing control joints or cracks with approved caulking is best. If movement occurs, structural foam injection can easily lift the pool back to its original position. If you want to learn more about how these repairs are done, feel free to contact us at /www.vestafoundationsolutions.com or give us a call at 1-405-565-9868
Additional Causes of Pool and Deck Shifting
Beyond the common culprits of uncompacted soil, water washout, and drought, several other factors can cause your pool and the surrounding deck to shift. Sometimes, the problem starts before the first splash is ever made, stemming from the materials and methods used during construction. Other times, the environment around your pool, like growing trees or the pressure of groundwater, can create instability over the years. Understanding these additional causes can help you pinpoint exactly what’s happening in your backyard and why your concrete is no longer on the level. It’s all about knowing what to look for, both under the ground and on the surface.
Poor Backfill Material
When your pool was installed, a significant amount of dirt was excavated. After the pool shell was in place, that space needed to be filled back in. The material used for this backfill is incredibly important. Some builders might use the excavated dirt to save on costs, but this can cause major issues. As one expert notes, “When builders use dirt instead of clean gravel to fill the space around the pool, it causes problems. Dirt holds water and shrinks over time, creating empty spaces that the pool can sink into unevenly.” This creates voids beneath your deck, leading to the sinking and cracking you’re trying to avoid.
Hydrostatic Pressure
Water is powerful, and when it collects in the soil underneath your pool, it can exert an incredible amount of upward force. This is known as hydrostatic pressure. In-ground pools are heavy, but if enough water builds up beneath them with nowhere to go, that pressure can actually lift the pool shell. This phenomenon can make a pool “float” right out of the ground, especially if the pool is empty or has been drained for maintenance. This upward movement will inevitably crack and shift the surrounding concrete deck, causing significant and costly damage to your entire pool area.
Frost Heave
Even here in Arkansas, our winters can bring freezing temperatures that affect the soil. When water in the ground freezes, it expands, and this expansion can push soil, rocks, and even concrete slabs upward. This process is called frost heave. It’s a powerful force that can easily lift deck footings and concrete panels. The real problem occurs when the ground thaws. As one source explains, “Once a footing has been lifted by frost, it will not naturally settle back down because silt fills the void underneath.” This means that each winter, the problem can get progressively worse, leaving your deck permanently uneven.
Nearby Tree Roots
Those beautiful, mature trees providing shade for your backyard might also be the source of your deck problems. As trees grow, their root systems expand in search of water and nutrients, and they can easily grow underneath your pool deck. Large roots can exert enough pressure to lift and crack concrete slabs from below. Conversely, if a large tree near the pool dies or is removed, its decaying roots can leave behind large voids in the soil. This loss of support can cause the deck to settle and sink into the newly formed empty spaces, creating dangerous trip hazards.
Improper Construction
Unfortunately, sometimes the problem traces back to the very beginning. If the ground wasn’t properly compacted before the concrete was poured, it was bound to settle eventually. Poor site preparation is a common issue, as are construction flaws that allow water to get under the deck easily. If the builder didn’t ensure proper drainage or grade the area correctly, you might be dealing with the consequences years later. These initial mistakes create a weak foundation for your pool deck, making it much more susceptible to shifting and cracking from soil movement and water intrusion over time.
Warning Signs of a Shifting Pool Deck
Spotting a shifting pool deck early can save you a lot of headaches and money down the road. While a large crack is an obvious red flag, some of the initial warning signs are much more subtle. It’s a good idea to walk around your pool every so often and just take a look. Pay attention to the little details—the water level, the lines where the deck meets the pool coping, and the feel of the concrete under your feet. Catching these issues early gives you more options for repair and can prevent a small problem from turning into a major structural failure.
Uneven Waterlines
Your pool’s water level can be one of the most reliable indicators of a problem. Take a look at the waterline on the tiles inside your pool. Is it perfectly even all the way around? If the water appears higher on one side and lower on the other, it’s a strong sign that the entire pool shell has tilted or shifted. This isn’t an optical illusion; it’s a clear signal that the ground underneath has moved, causing one part of your pool to sink or be pushed upward. This is one of the first things you should check if you suspect something is wrong.
Cracks and Gaps
Cracks are one of the most common signs of foundation problems, and your pool deck is no exception. Look for cracks in the concrete surface, especially radiating out from the corners of the pool. You should also inspect the expansion joint where the deck meets the pool coping. If you see a widening gap here, it means the deck is pulling away from the pool itself. These cracks and gaps are more than just cosmetic flaws; they are entry points for water, which will only worsen the soil issues underneath and accelerate the damage.
Bulging Pool Walls
Take a close look at the walls of your pool. Do they still look perfectly straight, or do they appear to be bulging inward or bowing outward? This is often caused by excessive pressure from saturated, expansive clay soils pushing against the pool structure. When the soil outside the pool is constantly wet, it swells and exerts immense force on the walls. This is a serious structural issue that indicates significant ground movement and pressure, and it needs to be addressed by a professional before it leads to a catastrophic failure of the pool wall.
Hollow Spots Under the Concrete
Sometimes, the problem is a void that has formed underneath the concrete slab. This happens when soil washes out or shrinks, leaving an empty space. You might not see it, but you can often detect it. Look for sunken areas or slabs that seem to be tilted. If you tap on the concrete with a hammer or a heavy object and it sounds hollow, that’s a tell-tale sign of a void. Puddles of water that form on the deck after it rains can also indicate a low spot where the concrete has settled into a hollow area below.
Repair Methods and Solutions for Pool Decks
If you’ve noticed cracks, gaps, or uneven slabs around your pool, don’t panic. The good news is that there are effective, long-term solutions available that don’t necessarily involve tearing everything out and starting over. Modern repair methods can lift and stabilize your existing concrete, while smart water management can prevent the problems from coming back. The key is to address the root cause of the shifting—the unstable soil underneath—rather than just patching up the surface. With the right approach, you can restore your pool deck’s safety, function, and appearance for years to come.
Concrete Lifting
One of the most effective ways to fix a sunken pool deck is with a method called polyurethane foam injection. This technique is minimally invasive and remarkably fast. Professionals drill small, dime-sized holes through the sunken concrete slab. Then, a high-density, structural-grade polyurethane foam is injected into the void beneath. The foam expands within seconds, filling the empty space and gently lifting the concrete back to its original, level position. This process not only corrects the unevenness but also stabilizes the soil underneath, preventing future sinking.
Fixing Frost Heave Damage
If frost heave is the culprit behind your shifting deck, a surface-level fix won’t last. The only permanent solution is to address the footings that have been lifted by the frozen ground. This typically involves excavating around the affected footings, resetting them, and ensuring they are placed below the local frost line. According to experts, the new holes for the footings “must be at least one foot deeper than your local frost line” to prevent the issue from happening again. This is a more intensive repair, but it’s necessary to stop the cycle of winter lifting.
Deck Resurfacing
For decks with minor surface issues like hairline cracks, discoloration, or spalling, resurfacing can be a great option. This involves applying a thin cement-based overlay to the existing concrete, which can be stamped or stained to create a fresh, new look. However, it’s crucial to understand that resurfacing is a cosmetic fix. It will not solve underlying structural problems like sinking or instability. If your deck has settled, you must address the soil issues and lift the concrete *before* considering a resurfacing project, or the new surface will just crack again.
Water Management Solutions
Since water is the root cause of most pool deck problems, managing it effectively is the best long-term solution. This starts with ensuring proper drainage around your entire pool area. Your yard should be graded so that water flows away from the deck, not toward it. Check that your gutters and downspouts are clear and are discharging water several feet away from the pool. By controlling the source of the water, you can prevent soil washout and reduce the hydrostatic pressure that leads to so many foundation repair issues.
Installing a Hydrostatic Pressure Relief Valve
For pools in areas with a high water table, a hydrostatic pressure relief valve is essential. This simple device is installed in the bottom of the pool and acts as a one-way valve. It allows groundwater from underneath the pool to enter the pool if the pressure gets too high, but it won’t let pool water leak out. This effectively “acts like a sump pump for your pool,” preventing the dangerous buildup of hydrostatic pressure that can lift the entire structure.
Sealing Joints and Cracks
The expansion joints around your pool deck and any cracks that have formed are like open doors for water. Rain and pool water can flow directly into these openings, eroding the soil base beneath the concrete. Regularly inspecting and sealing these joints and cracks with a flexible, waterproof polyurethane caulk is a simple but critical maintenance step. This prevents water from getting where it doesn’t belong and helps keep the soil under your deck stable and dry, which is key to preventing future movement.
What to Do When Your Pool Deck Shifts
Discovering that your pool deck is shifting can be unsettling, but having a clear plan of action makes all the difference. Instead of jumping to conclusions or worrying about a worst-case scenario, it’s best to take a methodical approach. The right steps involve a little bit of patience, some research into your original construction agreement, and, most importantly, getting a professional opinion. By following these steps, you can accurately diagnose the problem, understand your options, and make an informed decision about the best way to move forward with a permanent repair.
Understanding Repair Timelines
If your pool is relatively new, it might be wise to wait before rushing into a major repair. The soil around a new pool needs time to fully compact and settle, a process that can take a full cycle of seasons. Some experts advise waiting about a year to let the ground stabilize before making any repairs to the deck. This ensures that you’re fixing a problem that has fully manifested, rather than patching a crack that will continue to grow as the ground continues to settle. Patience now can prevent you from having to pay for the same repair twice.
Checking Builder Responsibility and Warranties
Before you call a repair company, pull out the contract you signed with your pool builder. Review it carefully to see what it says about warranties for workmanship and structural integrity. If your pool is only a year or two old, the shifting may be covered under the builder’s warranty. The language in your contract is very important, as it will define who is responsible for fixing issues related to poor compaction or improper construction. Document the damage with photos and contact your builder to discuss the problem and see if it falls under their responsibility.
Getting an Expert Opinion
To truly understand the cause and extent of the problem, you need a professional assessment. It’s a good idea to “hire an independent expert to look at the problem and figure out the exact cause.” A foundation repair specialist can evaluate the soil conditions, the deck’s construction, and the drainage around your property to give you a complete picture of what’s going on. At Vesta, we provide thorough inspections to identify the root cause of the issue and recommend a permanent solution tailored to your home. Getting an expert opinion is the most important step toward restoring your peace of mind and your pool deck.
Frequently Asked Questions
Are a few small cracks in my pool deck really a big deal? It’s easy to dismiss a small crack as normal wear and tear, but it’s often the first sign that the soil underneath your deck is shifting. Think of that crack as an open invitation for water to seep below the concrete, which can wash away soil and make the problem worse over time. Addressing the cause of a small crack now can prevent it from turning into a large, uneven trip hazard later.
Can I just fill the cracks myself with a product from the hardware store? You certainly can patch a crack, but it’s important to know that this is only a cosmetic fix. Using caulk or a patching compound will cover the crack, but it won’t solve the underlying issue of unstable ground that caused the concrete to move in the first place. The slab will likely continue to shift, and that crack will probably reappear. A true repair involves stabilizing the soil to prevent further movement.
How does the foam injection process work? Is it a permanent fix? Polyurethane foam injection is a straightforward and effective way to lift and support sunken concrete. We drill a few small, dime-sized holes in the slab and inject a special foam into the empty space beneath it. This foam expands to fill any voids, lifting the concrete back to its proper level and stabilizing the soil. Because the material is waterproof and incredibly durable, it provides a strong, long-lasting solution.
Will fixing my pool deck tear up my entire backyard? Not at all. One of the best things about using polyurethane foam to lift concrete is how minimally invasive it is. The process doesn’t require heavy machinery or large-scale demolition. We work with small equipment, the holes we drill are tiny, and the job is typically completed quickly. Your landscaping and yard will remain intact, so you can get back to enjoying your pool right away.
My pool and deck are pretty old. Is it still possible to lift the concrete? In most cases, yes. The age of the concrete isn’t as important as its current condition. As long as the concrete slabs aren’t completely crumbled or broken into many small pieces, they are usually great candidates for lifting. A professional assessment can determine if the slabs are sound enough to be lifted and stabilized for many more years of use.
Key Takeaways
- The Problem Starts in the Soil: A shifting pool deck is rarely an issue with the concrete itself; it’s a sign of unstable ground underneath. Poorly compacted dirt from the original pool installation, water erosion, or drought can cause the soil to settle, leaving your concrete without support.
- Watch for the Early Warning Signs: You can often catch a shifting deck before it becomes a major hazard by looking for subtle clues. Pay attention to an uneven waterline in the pool, new cracks or gaps forming, or concrete slabs that sound hollow when you tap on them.
- Address the Cause for a Lasting Fix: The best repair is one that solves the root problem. Professional solutions like polyurethane foam injection lift the concrete and stabilize the soil beneath it, while improving drainage around the deck helps prevent the issue from happening again.