Swimming pools are one of the most enjoyable and luxurious additions to any home. Whether you’re soaking up the sun or enjoying a cool dip during summer, your pool provides more than just recreation—it enhances your property value and lifestyle. However, one of the more alarming issues that pool owners may face is the discovery of cracks in the pool structure.
You might be asking: Are pool cracks normal? The short answer is yes—but not all cracks present the same level of danger. Understanding why pool cracks occur, when they become a real concern, and what you can do about them is crucial for maintaining the safety, longevity, and aesthetics of your pool.
This comprehensive guide explores the types of cracks common in different types of pools, the reasons they occur, how to assess their severity, and options for repair or replacement. It also includes expert advice on prevention and maintenance strategies.
Understanding Pool Construction and Material Types
Before determining whether pool cracks are “normal,” it’s important to understand the type of pool you own and the materials used in its construction. The frequency, appearance, and implications of cracks can vary depending on whether your pool is fiberglass, concrete (gunite), or vinyl-lined.
Concrete (Gunite or Shotcrete) Pools
Concrete pools, often called gunite or shotcrete pools, are durable, long-lasting, and highly customizable. They are formed using steel rebar and sprayed with a concrete and sand mixture.
Because concrete can shrink and crack during the curing process, it’s not uncommon for these pools to develop small hairline cracks shortly after construction. These are often normal and not a sign of structural failure.
Key Point: Hairline cracks in concrete pools are common, especially if they appear within the first year.
Fiberglass Pools
Fiberglass pools are constructed off-site and then lowered into the ground. Their structure is much more solid and less affected by environmental shifts such as ground movement. However, they are not immune to cracking—especially if installed improperly or exposed to significant pressure changes.
Fiberglass pools may develop cracks around fittings, where the wall meets the floor, or from issues in installation-related shifting. However, unlike concrete pools, cracks of any size in fiberglass pools tend to be a more urgent concern.
Vinyl Liner Pools
Vinyl liner pools are structured with walls made of steel, aluminum, or polymer and lined with a flexible vinyl layer. These pools do not typically develop cracks in walls or foundations, but rather tears or punctures in the liner.
Because the walls are not poured, cracks in the structural frame are rare. However, if cracks form in the surrounding deck or wall structure, it may indicate foundational issues.
What Causes Cracks in Swimming Pools?
Understanding the reasons cracks form in swimming pools can help you determine if your cracks are normal or indicative of a larger issue.
Natural Settling and Structural Movement
After installation, every pool will experience some degree of settling. In the case of concrete pools, hairline cracks can develop as a result of the initial settling process. This is because concrete is susceptible to thermal contraction, expansion, and minor movement in the ground. In most instances, these micro-cracks are not harmful and can be sealed easily.
Ground and Soil Movement
When the soil beneath or around your pool shifts—due to seasonal freezing and thawing, drought, or seismic activity—it can cause stresses in the pool structure. Areas with expansive soils like clay are particularly prone to this issue.
| Soil Type | Description | Effect on Pool |
|---|---|---|
| Clay | Expands when wet, shrinks when dry | Can create upward pressure or settling issues |
| Silt | Medium compressibility | Stable but requires proper compaction |
| Sand | Well-draining, low expansion | Generally favorable for pool construction |
Poor Installation Practices
If a pool isn’t constructed with proper engineering or materials, it is much more likely to develop more significant cracks over time. Issues such as improperly reinforced walls, insufficient base preparation, or poor water chemistry management can all accelerate deterioration and weaken the pool structure.
Hydrostatic Pressure
Water buildup beneath the pool—known as hydrostatic pressure—can cause a concrete pool to crack or even float out of the ground if the hydrostatic relief valve fails. This typically occurs during periods of heavy rain or a rising water table.
Freeze-Thaw Cycles
In colder climates, water trapped in small cracks or joints can freeze, expand, and widen the cracks over time. This can impact concrete and vinyl liner pools more than fiberglass pools.
Types of Pool Cracks Defined
Not all pool cracks are equal. Depending on location, length, and width, some are cosmetic while others require immediate attention.
Hairline Cracks
These are very thin cracks, often less than 1/16 of an inch wide. Hairline cracks are common with new concrete pools and are normally not a serious concern. They may appear in various places like the floor, walls, or steps.
Structural Cracks
These cracks are larger in width, often extending through multiple surfaces of the pool (walls to floor). Structural cracks may signal deeper issues such as foundation problems, soil movement, or poor construction and should be assessed by a professional.
Vertical and Horizontal Cracks
Cracks in the pool can appear vertically or horizontally. Vertical cracks can be caused by vertical shifts in the soil. Horizontal cracks are common on the upper portion of the walls and may be tied to poor reinforcement or excessive pressure from surrounding soil.
Cracks Around Fixtures
Cracks developing near pool lights, inlets, or drains may be linked to either installation problems or long-term wear and stress. This is especially true with fiberglass pools, where the material doesn’t flex as much as concrete.
Are Pool Cracks Normal? What’s Okay and What’s Not
While the discovery of a crack in your pool can be unsettling, the presence of cracks isn’t inherently abnormal.
When It’s Normal
Concrete pools in particular are expected to develop light hairline cracking. In many cases, this cracking occurs during the first two years due to natural settling and minor ground movement. If the cracks are not widespread and do not allow water leakage, they’re typically not a concern.
When It’s a Problem
If you’re noticing any of the following, you may have a serious underlying problem:
- Cracks wider than 1/8 inch that feel like actual gaps under your fingers.
- Step or wall displacement, where adjacent pieces don’t align anymore.
- Staircase effect—one corner of the pool has dropped or risen significantly.
- Water loss that can’t be attributed to evaporation or equipment issues.
Important: Cracks in fiberglass pools or around fittings should not be considered normal, especially if water leakage is observed.
How to Assess Your Pool Cracks
Before jumping to conclusions, follow these steps to determine whether pool cracks warrant professional expertise:
Step 1: Visual Inspection
Start by walking around your pool and inspecting all areas—walls, bottom, coping, and surrounding decking. If there’s a noticeable crack with any depth or dimension, note its location and approximate width.
Step 2: Check for Water Leaks
Leave the pump off for several hours and see if the water level drops. A drop of an inch or two may be due to evaporation. A loss greater than 1/4 inch per day may indicate a leak.
Step 3: Pool Leak Test
Fill a plastic bucket with pool water up to the same level as the pool, mark both levels, and leave them overnight. If the pool water drops faster than the bucket, there is likely a leak.
Step 4: Use a Crack Monitoring Template
Some professionals use special transparent overlay templates to monitor crack growth week to week. These can help determine whether the issue is ongoing or stable.
Repair Options for Pool Cracks
Once you’ve confirmed a crack in your pool, choose the appropriate method of repair based on the severity of the issue.
Minor Crack Repairs
For hairline or very small cracks in a concrete or plaster pool surface:
- Drain the pool to just below the crack.
- Clean and open the crack with a chisel or crack injection tool.
- Apply an epoxy or flexible crack filler.
- Seal and replaster the area if necessary.
Note: These repairs are only recommended for cracks with no structural or hydrostatic implications.
Major Structural Repairs
Cracks that have depth, width, and active signs of movement may require:
- Digging behind the affected wall to allow for expansion space and install a weeping tile system.
- Reinforcing the wall with tie-back anchors or steel beams.
- Injecting deeper cracks with structural foam or expanding grout to support shifting soils.
Such repairs may necessitate a professional pool contractor or structural engineer.
Fiberglass Pool Repairs
Fiberglass requires professional repair techniques such as:
- Sanding down the affected area.
- Laminating new gel-coat and fiberglass layers over the damaged spot.
- Sealing and ensuring the new application matches the original finish.
However, extensive wall cracks often make full resurfacing or replacement a more viable solution.
Vinyl Liner Repairs
Most vinyl pool cracks are not structural—they occur in the liner. Vinyl leaks can be patched with a specially formulated adhesive and liner patch, but large tears often require full replacement.
When to Call a Professional Pool Contractor
There are specific situations where relying on your own skills or store-bought repairs could worsen the situation.
Indications for Expert Involvement
- The crack is deep, widening, or shows visible water seepage.
- There’s a sudden increase in your water bill, indicating a leak.
- Surrounding concrete is crumbling, sinking, or heaving unevenly.
- You’ve noticed signs of water infiltration in adjacent structures (garage, patio, wall).
A licensed pool technician can help perform pressure tests, ground analysis, and coordinate with local waterproofing experts or foundation repair companies if needed.
What to Expect
Professional diagnostics often involve using:
- Dye leak tests for pinpointing exact leak locations.
- Moisture meters to measure wall saturation levels.
- Ground-penetrating radar or camera inspections for hidden cracks.
They may suggest resurfacing, structural reinforcement, or even total pool renewal, depending on the severity of the damage.
Damage Prevention: How to Avoid Pool Cracks
It’s always better to avoid pool cracks than to fix them later. Here are some effective preventative steps to consider:
Professional Installation Is Key
Ensure that your pool is installed by experienced, licensed contractors with knowledge of local geology and soil conditions. A poorly installed pool is at a much greater risk for early structural issues.
Maintain Proper Water Chemistry
Unbalanced pH, alkalinity, or calcium levels can attack the plaster and corrode the surfaces that hold the structural shell together. This can cause small cracks to become bigger over time.
Address Drainage Challenges Promptly
Surface water and pool pumps that discharge water too close to the pool can cause water to pool near the foundation, leading to soil erosion or saturation.
Monitor Seasonal Changes
During winter, ensure that your pool is winterized correctly. In spring, inspect the coping, tile, and decking for early signs of wear and potential crack formation.
Perform Annual Inspections
Just like your car or HVAC system, your swimming pool deserves routine maintenance and inspections. Annual checks often catch small cracks before they turn into major structural damage.
Conclusion: Pool Cracks—Normal but Worth Monitoring
In summary, yes, pool cracks are normal—especially in concrete pools. However, normality doesn’t negate vigilance. Whether it’s a small hairline crack or a large structural fracture, identifying the issue early and knowing when to act can protect your investment and extend the life of your pool.
Not all cracks spell disaster, but ignoring them always does.
If you’ve found cracks in your pool—and especially if you’re unsure of the origin and seriousness—it’s wise to bring in a licensed pool professional for an expert evaluation. Preventive maintenance, regular inspections, and prompt repairs can keep your pool beautiful, functional, and leak-free for decades.
What causes cracks in pool surfaces?
Cracks in pool surfaces can occur for several reasons, ranging from the natural aging of materials to structural issues in the foundation. One common cause is the settling of the ground beneath the pool over time, which can create shifts and stress points in the structure. Temperature fluctuations also play a role, as materials like concrete and plaster can expand and contract, leading to surface stress and eventual cracking.
In addition to environmental factors, improper installation or subpar construction materials can lead to cracks developing sooner than expected. Poorly mixed plaster, insufficient rebar support, and inadequate curing of materials during construction weaken the pool shell. Another cause can be high water or hydrostatic pressure from the surrounding soil pushing up from beneath, especially if the water table is high or the pool has been drained. Each of these factors contributes to different types of cracks, some of which are minor while others may indicate serious structural damage.
Are all pool cracks normal and acceptable?
Not all pool cracks are normal or acceptable, though some types and sizes of cracks may be expected over time. Hairline cracks—thin, superficial imperfections—are somewhat common, especially in concrete pools, and may not pose immediate danger. These often appear due to shrinkage during the curing process or slight shifts in the earth around the structure. However, they should still be monitored as they can develop into more serious issues if left unaddressed.
Wider cracks, especially those that are uneven, step-like, or extensive in nature, are typically signs of more serious structural problems. These should not be ignored, as they can lead to water leakage, weakening of the pool framework, or even safety hazards. Determining whether a crack is normal involves evaluating its location, size, direction, and progression, ideally with the help of a pool professional who can perform a detailed inspection.
How can I tell if a pool crack is serious?
The seriousness of a pool crack can often be determined by its size, pattern, and location. Hairline cracks that are narrow and uniform are usually minor and may be cosmetic. On the other hand, vertical or diagonal cracks that are wider than 1/8th of an inch, step cracks in tiled pools, or cracks accompanied by signs of shifting, such as sloped surfaces or broken tiles, are often an indication of structural movement and require expert attention.
Another indicator of a serious issue is whether the crack is contributing to a water loss problem. If the pool requires frequent refilling or shows signs of moisture near the surrounding deck or equipment pad, there may be an underlying leak. In such cases, the crack is no longer just a cosmetic concern but a potential source of long-term damage. A certified pool inspector or structural engineer can conduct tests to assess the integrity of the shell and recommend the appropriate repair.
What are the risks of ignoring pool cracks?
Ignoring pool cracks can lead to a variety of problems, especially when they are structural in nature. The most immediate issue is water leakage, which not only increases water bills but can also erode the soil around or beneath the pool, creating further settling or voids that compromise the support structure. Over time, this can result in more extensive damage, costlier repairs, and even the need for full structural renovation or demolition.
Additionally, untreated cracks can become breeding grounds for algae, bacteria, and other contaminants that are difficult to clean and may pose health concerns. In plaster or concrete pools, exposed aggregate beneath cracks can cause rough or jagged surfaces, increasing the risk of injury to swimmers. From a safety perspective, cracked areas in vinyl-lined pools may jeopardize the integrity of the entire liner, leading to tears or punctures that allow the pool to collapse. Addressing cracks early helps prevent both health and financial issues.
What are the common remedies for pool cracks?
For minor, non-structural cracks—such as hairline fractures—resurfacing or patching materials are often sufficient. Products like epoxy grouts or flexible crack fillers can seal these surface imperfections and prevent further expansion. In some cases, a professional may recommend pressure washing and plastering the entire pool surface to restore aesthetics and consistency in the finish.
For more significant structural cracks, the solution usually involves more invasive procedures. This can include chipping out the cracked area, reinforcing with new steel or rebar, and applying shotcrete or marcite to restore the shell’s integrity. In extreme cases, full resurfacing or reconstruction may be necessary. Modern solutions also include the use of hydraulic cement and advanced sealants designed specifically for underwater applications. Consulting a qualified pool contractor is key to choosing the most appropriate remedy for the damage observed.
Can pool cracks be prevented altogether?
While it’s difficult to completely eliminate the possibility of cracks in a swimming pool, proper design, construction, and maintenance can significantly reduce the risk. Choosing a reputable contractor who follows industry standards for pool construction is crucial. This includes proper soil stabilization, adequate rebar installation, and the use of high-quality materials that are suitable for the local climate and ground conditions.
Ongoing pool care and maintenance also play a major role in prevention. Keeping water chemistry balanced prevents surface degradation, while regular inspections allow small issues to be identified and addressed before they escalate. Draining the pool only when necessary and under professional supervision helps reduce pressure imbalances. In areas with high water tables, proper hydrostatic pressure relief systems should be installed during construction. These precautions can greatly improve the longevity of the pool and minimize the likelihood of cracks.
When should I consult a professional about pool cracks?
It’s best to consult a professional as soon as a crack becomes noticeable, especially if its size or pattern raises concern. Early detection can prevent further damage and help reduce long-term repair costs. If the crack appears suddenly, grows over time, or is accompanied by tile movement, sloped decks, or water loss, a professional assessment becomes even more critical.
A qualified pool contractor or structural engineer can inspect the crack using specialized tools and provide an accurate diagnosis of the cause and severity. They can determine whether it’s a cosmetic issue that can be patched or a deeper structural problem requiring more extensive repairs. Additionally, a professional evaluation is helpful when dealing with warranties or insurance claims related to pool damage. Prompt expert consultation ensures safety, functionality, and proper maintenance of your swimming pool.