Installing an above ground pool is an exciting project, but the key to a safe and lasting setup starts at ground level. If you’re wondering what to put under above ground pool on grass, you’re asking the right question from the start. Preparing the ground properly before installing an above-ground pool is crucial for its longevity and stability. A good foundation prevents liner damage, keeps the water level, and stops weeds from poking through.
This guide will walk you through every step and material option. We’ll cover why grass alone is a bad idea and how to create a perfect base. You’ll learn about different padding materials, their costs, and how to install them correctly.
What To Put Under Above Ground Pool On Grass
You cannot place your pool directly on a lawn. Grass is uneven, holds moisture, and will quickly die and decompose, creating a soft, unstable mess. You need a protective barrier system. The best setup uses a combination of materials for stability, padding, and protection. Here is the standard, recommended layering system from the ground up:
- Ground Preparation: Leveled and compacted soil.
- Weed Barrier: A geotextile fabric to block growth.
- Base Layer: Sand or a commercial pool pad for a smooth surface.
- Protective Padding: A foam pad or specialized ground cloth.
- Pool Liner: Your pool’s final interior layer.
Each layer serves a specific purpose. Skipping one can lead to problems like punctures, uneven settling, or an uncomfortable floor. Let’s break down each component in detail.
Essential Materials For Your Pool Base
Choosing the right materials is the most important decision you’ll make. Here are the common options, with their pros and cons.
Sand: The Traditional Choice
Mason sand or pool filter sand is a classic base material. It’s affordable and easy to work with, allowing for precise leveling. You need a layer about 2 inches thick. However, sand can shift over time, wash away during heavy rain if not contained, and attracts insects like ants. It also provides minimal cushioning on its own.
Commercial Pool Pads (Foam Pads)
These are interlocking foam tiles or rolled sheets made specifically for pools. They offer excellent cushioning and protection against rocks and roots. They create a very comfortable floor to walk on. The downside is the higher upfront cost compared to sand, but they are durable and often reusable.
Geotextile Fabric (Ground Cloth)
This is a non-woven fabric that acts as a critical weed and grass barrier. It is permeable, allowing water to drain through while blocking plant growth. It should always be placed directly on the leveled soil, beneath your sand or foam pad. Never use a plastic tarp, as it will trap moisture and promote mold and rot.
Crushed Stone or Gravel
For areas with poor drainage, a base layer of finely crushed stone or gravel can be used under the sand. This aids in water run-off and prevents pooling underneath. It must be thoroughly compacted and covered with fabric before adding sand to prevent it from mixing.
Carpet Padding (A Temporary Fix)
Some people use old carpet or carpet padding. While it provides cushioning, it is not recommended. It retains moisture, breaks down quickly, and can harbor mold, mildew, and insects. It’s a short-term solution that often leads to long-term problems.
Step-By-Step Installation Guide
Now that you know the materials, here is the detailed process to install your pool base correctly. Rushing this stage is the biggest mistake new pool owners make.
Step 1: Mark and Clear the Area
Mark a circle or oval that is 12-24 inches wider than your pool’s diameter on all sides. This gives you room to work. Remove all grass, sod, roots, and large rocks from this entire area. You need to get down to bare soil.
Step 2: Level the Ground
This is the most critical and labor-intensive step. The ground must be perfectly level. Use a long, straight 2×4 board with a carpenter’s level on top. Check for high and low spots across the entire area. Remove soil from high spots; never add soil to low spots to fill them, as it will not compact properly. A laser level can make this job much easier.
Step 3: Compact the Soil
Once level, use a manual tamper or a mechanical plate compactor to firmly pack the soil. A solid, compacted base prevents future settling and shifting. Walk over the entire area repeatedly to check for soft spots and compact them further.
Step 4: Lay the Geotextile Fabric
Roll out the weed barrier fabric over the entire compacted area. Overlap seams by at least 6 inches. This fabric will prevent any remaining grass or weeds from growing up into your pool base. Secure the edges with landscape staples or heavy objects.
Step 5: Add Your Base Layer
If using sand, spread a 2-inch layer evenly across the fabric. Use a rake and your leveling board to get it perfectly smooth and flat. If using a foam pad, unroll or interlock the tiles directly on the fabric. Ensure all seams are tight and the pad lies flat without wrinkles or gaps.
Step 6: Install Protective Padding
If you used sand, now add your protective foam pad on top. If you used a commercial pool pad as your base, this step may be combined. This top padding layer is your final defense against small imperfections and provides comfort.
Step 7: Assemble Your Pool
You are now ready to carefully assemble your pool wall and frame on top of the prepared base. Follow the manufacturer’s instructions precisely. Once the frame is up, you can install the liner, smoothing it out carefully to avoid wrinkles.
Common Mistakes To Avoid
Knowing what not to do is just as important as knowing the right steps. Avoid these frequent errors.
- Skipping Ground Leveling: An unlevel pool puts immense stress on the walls, risking collapse. Even a 1-inch difference is to much.
- Using Only a Tarp: Plastic tarps trap moisture, cause mildew, and offer no weed protection. They create a slippery, unstable layer.
- Ignoring Drainage: Ensure your site has a slight slope away from the pool area so rainwater runs off and doesn’t pool underneath.
- Forgetting the Wider Area: Preparing only the exact footprint leaves unstable edges. The wider prepared area supports the pool walls and your footsteps.
- Using Wood Chips or Bark: These organic materials decompose and create uneven, soft spots. They also attract pests.
Long-Term Maintenance Of The Base
Your job isn’t over once the pool is filled. Maintaining the area around and under your pool ensures its lifespan.
Keep the perimeter clear of leaves, dirt, and standing water. Ensure your lawn drainage continues to direct water away from the pool site. At the end of the season, if you disassemble the pool, inspect the base materials. Foam pads can be cleaned and stored. Sand may need to be leveled again or topped up if it has washed away. Replace any geotextile fabric that has torn.
For permanent installations, just monitor the ground around the pool for signs of sinking or erosion. Address any issues promptly before they effect the pool’s structure.
Cost Comparison Of Base Materials
Budget is always a consideration. Here’s a rough breakdown of material costs for a typical 24-foot round pool area.
- Geotextile Fabric: $30 – $60. An essential, non-negotiable cost.
- Sand (2-inch layer): $100 – $200. Cost varies by region and delivery fees.
- Basic Pool Ground Cloth (from kit): Often included, but thin. Upgrading costs $50 – $100.
- Interlocking Foam Tiles: $200 – $400. Higher initial cost but excellent durability and comfort.
- Rolled Foam Pad: $150 – $300. A good balance of cost and performance.
Investing in a better base upfront saves money on liner replacements, water loss from adjustments, and potential pool failure. It’s the foundation of your entire investment.
FAQ Section
Can I put an above ground pool directly on grass?
No, you should never place an above ground pool directly on grass. The grass will die, decompose, and create a soft, uneven base that can damage your pool liner and destabilize the structure. Always remove the grass and prepare a proper base.
What is the cheapest thing to put under an above ground pool?
The most budget-friendly option is a combination of geotextile fabric and a layer of mason sand. While sand is inexpensive, remember that it may require more maintenance over time and offers less cushioning than foam pads. Never skip the fabric to save money.
Is it better to use sand or a foam pad under a pool?
Foam pads are generally better for comfort, protection, and long-term stability. They provide a smooth, soft surface and block weeds effectively. Sand is a traditional, lower-cost option but can shift and settle. For the best results, many people use both: a sand base for leveling topped with a foam pad for protection.
How do I level the ground for a pool without digging?
Truly leveling ground almost always requires some digging. You must remove soil from high spots to match the lowest point. Adding soil to low areas creates an unstable fill that will compact unevenly. Using a rented sod cutter can make grass removal easier, followed by careful grading with a shovel and leveling tool.
Can you put an above ground pool on a slight slope?
No. The ground must be perfectly level for an above ground pool. Installing on a slope creates dangerous pressure differentials on the pool wall, which can lead to buckling or collapse. The entire installation site must be leveled before you begin assembly.