Planning a backyard pool is an exciting chapter for any homeowner—but it also comes with critical decisions that can impact the pool’s performance, safety, and longevity. One of the most overlooked yet vital aspects of a fiberglass pool installation is the choice of base material. While it might not be as glamorous as picking pool tiles or water features, your base material sets the foundation—literally—for how well your pool will hold up over time.
If you’re considering fiberglass pools in Toronto, where freeze-thaw cycles, groundwater levels, and soil conditions can be unpredictable, choosing between sand and gravel as a base is more than just a preference—it’s a matter of long-term durability.
The Role of Base Material in Pool Installation
Your fiberglass pool may be factory-moulded to perfection, but its success ultimately depends on what it’s sitting on. The base material used during fiberglass pool installation plays a major role in the following four performance pillars:
1. Stability
Your pool shell is only as stable as the surface it rests on. A poorly compacted or shifting base can cause the pool to settle unevenly, leading to cracks or bulging. A solid, well-drained base ensures that the pool remains level and secure for years.
2. Drainage
Water will always find its way through soil, and how your base handles drainage can make or break your installation. Inadequate drainage beneath a fiberglass pool can lead to hydrostatic pressure buildup, pushing the shell upwards—known as pool “floating”—or causing backfill washout.
3. Prevention of Bulging or Cracking
Fiberglass is flexible but not invincible. If the base is unstable or retains too much moisture, it can result in lateral pressure on the pool walls. Over time, this pressure may lead to unsightly bulges or structural cracks—both expensive and frustrating to repair.
4. Structural Longevity
Ultimately, the right base material adds decades to your pool’s life. It reduces the chances of shifting, settling, or drainage issues that lead to costly repairs. When properly chosen and installed, your base can safeguard your investment for the long haul.
Common Mistakes in Fiberglass Pool Installation Due to Poor Base Selection
Even the most experienced installers can make errors if they underestimate the importance of a proper base. Here are a few mistakes commonly seen:
- Choosing sand for budget reasons without accounting for local soil or weather conditions
- Inadequate compaction of the base material
- Ignoring proper slope and drainage design
- Failing to stabilize or contain shifting materials like sand on sloped yards
The lesson? Cutting corners on base materials might save you a few bucks today—but it can lead to major expenses tomorrow.
The Sand Base Method – Pros, Cons, and Best Use Cases
What It Is
Using sand as a bedding and backfill material has been a traditional method in fiberglass pool installation for decades. The idea is simple: a layer of fine sand is spread evenly on the excavated surface, leveled to support the pool shell, and often used again to backfill around the walls after placement.
Pros of Using Sand:
- Readily Available: Sand is easy to source, which makes it a go-to for many pool projects, especially in rural or suburban areas.
- Cost-Effective: Compared to gravel or engineered backfill, sand is typically cheaper, helping homeowners stay within budget.
- Easy to Work With: Sand can be shaped and leveled quickly, allowing for faster installation when conditions are ideal.
Cons of Using Sand:
- Prone to Shifting and Erosion: Sand doesn’t compact as solidly as gravel. If groundwater flows through the site, it can wash away sand, causing voids under the pool.
- Higher Risk of Settling and Pool Movement: Over time, especially in areas with high water tables (like many parts of Toronto), sand can settle unevenly, leading to structural stress.
- Moisture Retention: Sand retains water, which can increase hydrostatic pressure under the pool and lead to floating or bulging, especially during heavy rains or snowmelt.
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The Gravel Base Method – Pros, Cons, and Performance Benefits
When it comes to fiberglass pool installation, gravel has become the gold standard for professional builders—especially in regions like Toronto, where soil conditions and climate can put any pool structure to the test.
What It Is
The gravel method involves using crushed stone—often ¾-inch angular gravel—as both a bedding layer and backfill material around the fiberglass pool shell. Unlike rounded stones or sand, angular gravel locks into place when compacted, creating a firm and immovable base. It’s a strategy rooted in engineering science, and its performance benefits speak for themselves.
Pros of Using Gravel
1. Excellent Drainage
Gravel offers superior drainage compared to sand. Water can move freely between the angular stones, helping to prevent the buildup of hydrostatic pressure beneath the pool shell. This is especially important in fiberglass pools in Toronto, where snowmelt, rain, and groundwater can fluctuate significantly through the year.
2. Offers Firm and Stable Support
Unlike sand, gravel compacts into a solid base without shifting over time. This stability reduces the likelihood of pool settling, tilting, or structural distortion. The base remains solid even when water tables rise or fall.
3. Reduces Long-Term Movement or Shifting
Over the years, sand can settle, erode, or even wash away if not properly retained. Gravel, on the other hand, forms a more permanent structure. When properly compacted, it helps your pool maintain its level, reducing stress on the shell and plumbing.
4. Ideal for Freeze-Thaw Climates Like Toronto
In a city like Toronto, where winter temperatures can fluctuate above and below freezing, frost heave is a genuine concern. Gravel’s excellent drainage properties and low moisture retention prevent it from expanding during freezes, keeping your pool foundation safe from upheaval and damage.
Cons of Using Gravel
1. Higher Upfront Cost
There’s no denying that gravel is more expensive than sand. The material itself costs more, and installation requires additional labour and expertise. However, the upfront cost is often offset by fewer long-term repairs and a more stable installation.
2. Requires Experienced Installers
Gravel base installation is not a DIY-friendly process. It demands precision, proper compaction techniques, and sometimes geotextile fabric to ensure optimal results. That’s why it’s essential to work with professionals who specialize in fiberglass pool installation.
Sand vs. Gravel: Side-by-Side Comparison for Toronto Homeowners
Here’s a quick comparison to help you make an informed decision:
| Criteria | Sand | Gravel |
| Cost | Lower | Higher |
| Installation Ease | Easy | Needs precision |
| Drainage | Poor | Excellent |
| Long-Term Stability | Moderate to Poor | Excellent |
| Climate Suitability | Less Ideal for Freeze-Thaw | Great for Toronto Climate |
What Do Experts Recommend for Fiberglass Pools in Toronto?
If you ask seasoned pool builders and engineers what they recommend, the answer is overwhelmingly clear: gravel is the smarter choice for Toronto-area fiberglass pools.
Here’s Why:
1. Groundwater Management
Toronto properties often experience variable water tables depending on location and season. Gravel allows water to drain away from the base of your pool, reducing risks of “floating” or hydrostatic lift.
2. Frost Heave Resistance
Our region’s winter climate brings multiple freeze-thaw cycles. Sand can expand when saturated and frozen, pushing against your pool shell. Gravel doesn’t retain water, which helps eliminate this problem before it starts.
3. Slope and Soil Adaptability
Whether your backyard is flat or sloped, gravel conforms better to engineered grading, adds structural support, and integrates well with retaining walls or drainage systems.
4. Future-Proofing Your Investment
While gravel may add to your installation cost upfront, it helps prevent some of the most expensive issues down the line—such as re-leveling, plumbing damage, or cracking. For homeowners investing in a fiberglass pool installation, especially in Toronto’s unpredictable weather, gravel ensures peace of mind.
Final Verdict – Which Is Better for Your Backyard?
So, sand or gravel—what’s best for your backyard pool project? The answer depends on a few key factors: your budget, your soil conditions, and your long-term expectations.
Sand can be an acceptable base material under the right conditions—namely dry, well-drained soil and flat terrain. It’s inexpensive and quick to work with, making it a tempting option for budget-conscious homeowners. However, the downsides—like poor drainage, higher risk of shifting, and vulnerability to freeze-thaw damage—can lead to serious issues over time.
Gravel, on the other hand, is the clear winner in terms of performance and longevity. It offers unmatched stability, excellent drainage, and is highly suited for the variable weather and soil conditions in the Toronto area. Yes, it comes with a slightly higher initial cost and requires a skilled installer, but those are minor trade-offs when compared to the long-term durability and peace of mind it provides.
If you’re planning a fiberglass pool installation and want to make a one-time investment that stands strong for decades, gravel is hands-down the smarter choice—especially for fiberglass pools in Toronto, where nature doesn’t always play nice.
Looking to Invest in a Beautiful Swimming Pool in Toronto?
At Luxury Pools, we’ve built a reputation for precision, quality, and pools that are engineered to last. Our team specializes in pool design and installation tailored to the unique climate and soil conditions of Toronto and the GTA.
We don’t believe in shortcuts. That’s why we use premium materials like gravel and follow industry- practices to ensure your backyard oasis is as beautiful and structurally sound in year 10 as it is on day one.
Thinking about adding a swimming pool to your home? Let’s start with a free site assessment. We’ll evaluate your yard, answer your questions, and recommend the best approach for a flawless installation—one that fits your budget and stands the test of time.
Contact us at 416.504.5263 or email us at info@landcon.ca to book your consultation and take the first step toward transforming your outdoor space into the retreat you’ve always wanted.
