Putting Blocks under Pool Legs: Boost Stability and Prevent Damage

Setting up a backyard pool is exciting, but there’s one detail many people ignore: the ground under the pool legs. If you skip this step, your pool can become uneven, unsafe, or even get damaged. Using blocks under pool legs is a simple, smart way to protect your investment, keep your pool level, and make it last longer. But what kind of blocks should you use? How do you install them correctly? Are there hidden problems most pool owners don’t see until it’s too late? This guide answers all your questions about putting blocks under pool legs with clear steps, practical examples, and expert tips you won’t find in most instructions.

Why Blocks Matter For Pool Legs

When you fill a pool with water, it gets heavy—sometimes over 10,000 pounds for large above-ground pools. That weight pushes down on the legs. If the ground is soft, wet, or uneven, the legs can sink. This makes the pool lean or wobble, which is dangerous. Sometimes, the frame can even bend or break.

Blocks under the legs spread out the weight, so the ground doesn’t get damaged and the pool stays level. This simple step can make your pool safer and help you avoid costly repairs.

The Most Common Block Materials

Choosing the right block material is key. Not all blocks are the same. Some work better for certain pools and ground types. Let’s look at the most popular options and how they compare.

1. Concrete Pavers

Concrete pavers are the most popular choice. They’re strong, cheap, and easy to find at hardware stores. Standard sizes are 12×12 inches or 16×16 inches. These blocks support a lot of weight and don’t rot.

2. Patio Stones

Patio stones are similar to pavers but usually thicker and heavier. They’re perfect if you want extra strength, especially for larger pools. Because they’re flat and wide, they spread out the weight well.

3. Pressure-treated Wood

Sometimes people use pressure-treated wood (like 2×8 or 2×10 planks) cut into squares. These blocks are easy to cut and adjust to size. However, wood can rot over time if it stays wet, even if it’s treated.

4. Composite Deck Blocks

Composite deck blocks are made from recycled plastic and wood fibers. They’re resistant to rot and water, making them a modern, eco-friendly choice. They’re a bit more expensive but last longer than wood.

5. Brick

Bricks are used sometimes for smaller pools. They’re easy to stack and adjust, but a single brick is usually too small. You may need to use several together, which can shift if not set properly.

6. Metal Plates

Some pool owners use metal plates under legs, especially for pools with narrow, pointed feet. Metal spreads weight well but can rust unless coated. It’s not as common as other options.

7. Rubber Pads

Rubber pads are soft and can help absorb vibrations. They’re usually used on decks or patios, not on bare ground, because they’re not as strong as stone or concrete.

Comparing Block Types

Here’s a quick comparison to help you choose:

How Block Size And Thickness Affect Pool Safety

Many people pick the cheapest or smallest block to save money. But block size and thickness are critical. If the block is too small, the leg can slip off or sink into the ground. If it’s too thin, it can crack.

• For most above-ground pools, use blocks at least 12×12 inches wide and 2 inches thick.
• For larger pools (over 18 feet diameter), go bigger: 16×16 inches and 4 inches thick if possible.
• Always check the pool manual—some brands recommend specific block sizes.

A block that’s too big is better than one that’s too small. If you’re unsure, go larger.

Preparing The Ground Before Placing Blocks

Just dropping blocks on the grass is a common mistake. The ground under your pool legs should be flat, firm, and level. If the ground is soft or uneven, even the best blocks won’t help for long.

Follow these steps for proper preparation:

1. Mark The Pool Area

Use spray paint, string, or a garden hose to outline the pool’s shape.

2. Remove Grass And Roots

Dig up grass, weeds, and roots where the pool and blocks will go. This prevents sinking as organic material breaks down.

3. Level The Ground

Use a long board and a spirit level to check for high and low spots. Move soil around until it’s flat. This step can take time, but it’s crucial.

4. Compact The Soil

Use a hand tamper or rent a plate compactor. Firm, compacted soil supports weight better than loose dirt.

5. Add A Base Layer (optional But Helpful)

A thin layer of crushed stone or sand (about 1-2 inches) helps with drainage and makes leveling easier.

6. Double-check Level

The ground must be level, especially under each pool leg position.

Here’s a summary of the steps and why they matter:

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How To Place Blocks Under Pool Legs: Step-by-step

Once the ground is ready, it’s time to install the blocks. Here’s how to do it safely and correctly.

1. Lay Out The Pool Frame

Set up the empty pool frame where you want it. Don’t fill it with water yet. This lets you see exactly where each leg will rest.

2. Mark Leg Positions

Mark the spot for each pool leg with a small stake or spray paint dot. Double-check that all legs are spaced evenly.

3. Dig Shallow Holes For Each Block

For best results, dig a shallow hole (just deep enough so the top of the block will be level with the ground). This keeps the pool liner smooth and the blocks steady.

4. Place And Level Each Block

Set each block in its hole. Use a level to make sure it’s flat—side to side and front to back. Adjust as needed by adding or removing a little soil or sand under the block.

5. Check Height Consistency

It’s important that all blocks are at the same height. Use a long straight board and a level to compare blocks across the pool. If one block is higher, the pool will lean.

6. Assemble The Pool Frame

Once all blocks are in place and level, build the frame according to the pool’s instructions. Place each leg directly on its block.

7. Fill The Pool Slowly

As you add water, check each leg for movement or sinking. Adjust immediately if you see a problem—better now than later.

8. Add Finishing Touches

Backfill around each block with soil or sand to prevent gaps and keep them from shifting. Smooth out the liner, especially at the edge.

Mistakes To Avoid When Using Blocks

It’s easy to rush, but some common errors can cause big problems later.

• Skipping ground preparation

Blocks on soft or uneven ground will sink, even if they seem firm at first.

• Using thin or broken blocks

Blocks must be thick and in good shape. Cracked blocks fail under weight.

• Not leveling each block

Even a small tilt can throw off the whole pool.

• Wrong block size

Small blocks concentrate weight and increase sinking risk.

• Placing blocks above ground level

This creates a bump under the liner, leading to tears.

• Ignoring drainage

Poor drainage causes erosion and block shifting.

• Not checking during filling

Always watch for movement as water weight increases.

Real-life Example: What Happens If You Skip Blocks?

Let’s say you set up a 15-foot pool on your lawn, no blocks, just grass. After a week, you notice one side is lower. That’s because the legs are sinking into the soft earth. Water starts to spill out one side, and the frame bends.

This is not just a safety risk—it can void your warranty and ruin the pool. Fixing this means draining the pool and starting over, which takes time and money.

Now, imagine you use 12×12 inch concrete pavers under each leg. After a month, the pool is still level, the legs haven’t sunk, and your pool is safe for the kids. That’s the difference blocks make.

Seasonal Effects: How Weather Changes Impact Blocks

Many people don’t realize that weather affects blocks under pool legs.

• Rainy season: Wet soil gets soft, making blocks more likely to sink.
• Winter freeze: In cold climates, water in the soil can freeze and push blocks up (called “frost heave”). In spring, blocks may settle unevenly.
• Hot summers: Dry soil can shrink and create gaps under blocks.

To reduce weather problems:

• Use thicker blocks in wet or freezing areas.
• Make sure water drains away from the pool.
• Check block level at the start of each season.

What To Do If A Block Sinks Or Shifts

Even with careful setup, sometimes a block may settle over time. Here’s what you can do:

1. Stop Using The Pool

Safety first—don’t swim if the pool isn’t level.

2. Drain Water To Below The Leg

Remove enough water to take the weight off the sinking leg.

3. Remove The Leg And Block

Take out the block. Check if the soil underneath is soft or washed away.

4. Re-compact And Level The Area

Add more soil or gravel if needed, compact it well, and check for level.

5. Replace With A Stronger, Larger Block

Sometimes upgrading the block solves the problem.

6. Reinstall The Leg And Refill Pool

Watch closely for movement as you refill.

Can You Put Blocks Under The Whole Pool?

Some people ask: Can I put blocks under the whole pool, not just the legs? For small pools, you can use a solid pad (like patio stones or interlocking tiles) under the entire base. This gives full support and stops weeds. For larger pools, it’s usually better to support just the legs, because a hard floor can wear out the liner if not covered with foam or a protective pad.

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Special Tips For Different Pool Types

Pools come in many styles. Here’s how block choices change for each:

Metal Frame Pools (like Intex Or Bestway)

These have vertical legs that take most of the weight. Use strong, wide blocks. Always follow the manufacturer’s advice.

Inflatable Ring Pools

These spread weight more evenly, but blocks can help if the ground is soft or uneven.

Rectangular Pools

Make sure to support all corner and side legs. Corners take the most stress.

Soft-sided Pools

These usually don’t have legs but can still benefit from a solid, flat base to stop sinking.

Comparing Do-it-yourself Vs. Professional Installation

Is it worth hiring a pro to set up your pool base and blocks? Here’s how DIY and pro installations compare:

Most people can do it themselves if they’re careful and follow instructions. But for large or expensive pools, pros can save time and give peace of mind.

Non-obvious Insights Most Beginners Miss

1. Ground Shifts Over Time—even If It Looks Solid Today.

Rain, drought, and freeze-thaw cycles change the soil under your pool. Check block levels every few weeks, especially after heavy rain or before the swimming season.

2. Blocks Must Be Flush With The Ground, Not Above.

If blocks stick up, the pool liner can stretch over the edge and tear. Always set blocks so the top is even with the ground.

3. Blocks Can Hide Drainage Problems.

Water may pool around the blocks, washing away soil and causing shifting. Add gravel or sand around blocks for better drainage.

4. Check Local Codes And Rules.

Some areas require permits or have rules about pool installation. This can affect what materials you use.

Tools And Supplies You’ll Need

Having the right tools makes the job easier and safer. Here’s what you’ll typically need:

• Shovel
• Rake
• Hand tamper or plate compactor
• Long straight board (for leveling)
• Spirit level (2–4 feet)
• Measuring tape
• Spray paint or stakes
• Blocks (concrete pavers, patio stones, etc.)
• Sand or crushed stone (optional)
• Wheelbarrow (for moving soil)
• Garden hose (for marking area)

Safety Warnings

• Always wear gloves and sturdy shoes when handling heavy blocks.
• Don’t let children play near the work area.
• Never fill the pool until you’re sure every leg is supported and level.
• Check that no block wobbles or tips.

Where To Buy Pool Leg Blocks

You can find suitable blocks at:

• Home improvement stores (Home Depot, Lowe’s, Menards)
• Garden centers
• Landscape supply stores
• Online shops (Amazon, Walmart)

Ask for concrete pavers or patio stones in the outdoor section. If you want composite or rubber blocks, check specialty pool supply stores.

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How Much Does It Cost?

Costs vary by material and pool size:

• Concrete pavers: About $2–$6 each (most pools need 12–20 blocks)
• Patio stones: $4–$12 each
• Composite blocks: $8–$20 each
• Pressure-treated wood: $10–$20 for a 2×8 plank, cut into blocks
• Total cost: For a 15-foot pool with 16 legs, expect $30–$150 for blocks

It’s a small price compared to pool repairs or replacement.

Protecting Your Pool Liner

Your pool liner is soft and can tear if it rubs against sharp block edges. Here’s how to protect it:

• Set blocks level with the ground, not above.
• Place a liner pad or piece of old carpet over the block before setting the leg.
• Avoid using chipped or rough blocks.

When To Replace Blocks

Blocks last many years, but check them at the start and end of every season. Replace any that are:

• Cracked or broken
• Sinking or tilting
• Showing signs of rot (if wood)
• Rusting (if metal)

Additional Resources

For more detailed guides on pool installation and safety, visit the SwimmingPool.com website. They offer instructions, safety tips, and tools to help you get the most from your backyard pool.

Frequently Asked Questions

How Many Blocks Do I Need Under My Pool Legs?

Count the number of vertical legs on your pool frame. Each leg should have its own block. Most round pools have 12–18 legs; rectangular pools may have 10–24. Check your pool’s manual for the exact number.

Can I Use Wood Blocks Under My Pool Legs?

Pressure-treated wood can work for short-term setups, but it’s less durable than concrete or stone. Wood can rot or warp if it stays wet. If you use wood, make sure it’s thick, treated for outdoor use, and check it each season.

What Size Block Is Best For Pool Legs?

For most pools, use 12×12 inch blocks at least 2 inches thick. Larger pools may need 16×16 inch blocks or thicker stones. Always go bigger if you’re unsure—small blocks are risky.

Do I Need To Put Sand Under The Blocks?

You don’t have to, but a thin layer of sand (1–2 inches) under each block helps with leveling and drainage. Compact the sand well before placing the block. Avoid using too much, or the block may sink.

What Should I Do If My Pool Legs Start To Sink?

Stop using the pool right away. Drain water below the leg, remove and re-level the block and soil underneath, and use a larger or thicker block if needed. Never ignore a sinking leg—it can lead to pool collapse.

Setting up your pool on a solid, level base with quality blocks under the legs is one of the most important steps you can take. It keeps your family safe, protects your pool, and saves you money and headaches down the road.

Take the time to do it right, and enjoy a worry-free summer in your backyard oasis.