I bought an above ground pool to set on an existing concrete slab in my backyard. I realized after it arrived that the slab slopes a little on its long dimension, about 1 3/4" along the 24' length of the pool. The pool is 12' wide and the slab is flat along the width.

I'm think about setting something under the pool and support legs to help level it out, probably stair step it in 1/4" increments. Any ideas on what material to use? I'm thinking something in a 4'x8' board, moisture resistant, non-compressible, and able to handle a heavy evenly distributed load of the water sitting on it. Planning on putting down some 1/2" foam over the top of whatever I lay down to help smooth out the thickness step changes. Is cement board a good candidate, or is it too fragile?

Sand

If you know anyone at a sandblasting shop, they'll load you up for free

Why? The water in the pool is self-leveling.

If the water self levels and the pool walls are not, then the water will be high on one end

SockDePot said:

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Sand

If you know anyone at a sandblasting shop, they'll load you up for free

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How do I keep the sand in place? Frame it up? How do I get the frame level? Seems like I'd need to do some shimming, but that would let the sand out.

Ogre09 said:

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If the water self levels and the pool walls are not, then the water will be high on one end

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The slab is 24' and it's 1 3/4" out of level over that length. The pool is 12' wide. So, you're looking at max ~1" difference? When you're on one end 12' away, 1" isn't really noticeable - especially if you're in the pool and creating waves.

Tapcon 2x4s on the flat in a square at 12'-6" inside dimension. Then screw 2x4s on edge to the cleats. This will leave 12'-3" clear. Fill with sand and level. Set pool

As the above poster said... it'll be an inch or so difference in where the water is.

Are you really that worried about it? If so you should've have bought an above ground pool.

Old RV Ag said:

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Ogre09 said:

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If the water self levels and the pool walls are not, then the water will be high on one end

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The slab is 24' and it's 1 3/4" out of level over that length. The pool is 12' wide. So, you're looking at max ~1" difference? When you're on one end 12' away, 1" isn't really noticeable - especially if you're in the pool and creating waves.

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The pool is 24' long, so one end will be 1 3/4" deeper than the other. Not a ton, but noticeable.

TdoubleH said:

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Tapcon 2x4s on the flat in a square at 12'-6" inside dimension. Then screw 2x4s on edge to the cleats. This will leave 12'-3" clear. Fill with sand and level. Set pool

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Leave the sand low on one end so the sand is level? 4"x12'x24' of sand is nearly 5 tons.

Don't need to fill it full of sand. Level where needed. Skipped over the part of it being 24'. Was thinking a 12' round pool. Laying down an underlayment board sounds like a real PIA. I'd be afraid of uneven joints where tears in the liner can happen. Sand will allow you to go from 1-3/4" to nothing without rigid edges to cause damage or fasteners to come loose and poke a hole.

And you typically can't calculate sand volume like you would a liquid or say concrete. It would be less Volume. The more compacted, the closer you get but will still not be the true volume of cubic yards as a liquid. Maybe I'm wrong about that.

Always check slabs for FF and FL. Especially in a race shop!

I wouldn't worry about less than 2" delta in water level. No such thing as a level above ground pool anyway.

Rip a 2x trex to follow contour and fill with sand or paver base topped with sand.

I just did something similar for a stock tank pool on top of a sloping flagstone patio except I skipped the perimeter control.

A friend of mine has an above ground pool. Gets a new one about every three years, he's on pool three now. There isn't a lot of difference in elevation, but there's a little. First pool he tried to level it as best as possible before install, but it was a little bit off(half to 3/4 of an inch). Tried to fix the difference between pool one and pool two and it didn't really make much of a difference. He just installed pool number three a few months ago and didn't even try to do any adjusting to the dirt underneath. Too much of a pain in the ass.

Could just call it "the deep end".

Thanks folks. Ended up ignoring it