Project guide
Getting a perfectly level, smooth base under an above-ground pool liner.
An above-ground pool holds many tons of water and will find any imperfection in the ground beneath it. Out of level by an inch and the wall loads unevenly; a stone left under the liner becomes a puncture. The base has to be both dead level and completely smooth.
Mason sand or artificial turf sand for the final smoothing layer, over compacted road base limerock if the ground is soft. Mason sand is the traditional choice because it is fine, clean and screeds beautifully. Never use crushed stone directly under a liner.
For an 18 ft round pool, allow a 20 ft square = 400 sq ft. Two inches of mason sand is 400 x 0.167 / 27 = 2.47 cu yd, so order 3. If you need a base layer too, add 4 inches of limerock: 4.94 plus 20 percent, order 6.
Strip all sod and roots from an area two feet wider than the pool. Check level across the full diameter with a rotary laser or a long board and a spirit level; aim for under a half inch of variation overall. Spread sand two inches deep, screed it flat, then dampen and tamp. Walk the whole base barefoot before the liner goes down. Anything you can feel, the liner will find.
Materials for this job
Brick and block work, mortar, play areas and pool bases.
$35.00 / cu yd MaterialBase and infill under synthetic turf. Screened and consistent.
$18.75 / cu yd MaterialCompactable base under asphalt, concrete, pavers and driveways.
$31.25 / cu ydAbove-Ground Pool Base — common questions
Mason sand. It is fine, washed and screeds smooth, which is what a vinyl liner needs. Concrete sand and fill sand are too coarse.
Within about half an inch across the whole diameter. More than an inch and the wall is loaded unevenly, which is how above-ground pools fail.
About 2.5 cubic yards at two inches deep over a 20 ft square. Order 3 and keep the extra for levelling.
No. Organic material decomposes and settles, and roots come back through the liner. Strip to bare soil and build a proper sand base.
Pick your material, enter how many cubic yards and see the delivered number before you talk to anyone.