Cushion sand is a fine, screened sand used as a protective or leveling layer between surfaces in construction projects. It sits between a subgrade (the ground beneath) and whatever is being installed on top, such as a concrete slab, a moisture barrier, a pipe, or a pool liner. Its job is to create a smooth, even base that cushions the material above it from rocks, roots, and uneven soil below.
What Cushion Sand Is Made Of
Cushion sand is primarily silica sand that has been washed and screened to remove debris, rocks, and oversized particles. The grains are uniformly sized, typically falling between 0.15 mm and 0.6 mm, which gives the sand a fine, consistent texture. This uniformity is what makes it useful: the grains pack together tightly without leaving large voids, creating a stable, smooth surface.
The screening process also removes most fine dust particles. A good cushion sand contains 5 percent or less of very fine material (particles smaller than 0.075 mm). This matters because too much fine material traps water and turns the sand into mud, defeating its purpose as a free-draining base layer. You may also see cushion sand sold under names like “bedding sand” or “leveling sand” depending on the supplier, though the product is essentially the same: clean, uniformly graded, fine sand.
How It’s Used Under Concrete Slabs
One of the most common uses for cushion sand is beneath concrete slab foundations, particularly in residential construction. The sand is spread over the prepared subgrade to create a flat, level surface before a vapor barrier (a plastic sheet that blocks ground moisture) is placed on top. Industry guidelines recommend at least 3 inches of fine granular material beneath or around the vapor barrier to provide a permeable, absorptive base directly under the slab.
The sand layer serves two purposes here. First, it protects the vapor barrier from being punctured by sharp rocks or uneven ground. Second, it absorbs some of the moisture from the freshly poured concrete, which helps reduce drying shrinkage cracks. A 2 to 3 inch layer of damp cushion sand over the vapor barrier has been used specifically to minimize this type of cracking in thin slabs. For post-tensioned slab foundations in residential applications, specialists generally recommend placing the vapor retarder on top of the leveling sand, so the sand sits directly on the subgrade and the barrier goes between the sand and the concrete.
Pipe Bedding and Utility Trenches
Cushion sand is also the go-to material for pipe bedding, the layer placed at the bottom of a trench before a pipe is laid into it. According to Bureau of Reclamation standards, the bedding for both rigid and flexible pipe should be an uncompacted layer of select material, and that material needs to be cohesionless and free-draining with a maximum particle size no larger than 19 mm (about three-quarters of an inch).
For rigid pipes like concrete or clay, the sand bedding helps distribute the load from the soil above across the pipe’s surface. For flexible pipes like PVC, the sand surrounding the pipe (called the embedment zone) resists deflection, keeping the pipe from being crushed or deformed under pressure. The embedment sand must be compacted to at least 70 percent relative density to provide adequate support. This is why you’ll often see utility contractors carefully packing sand around water lines, sewer pipes, and electrical conduits before backfilling a trench with regular soil.
Pool Liner Protection
If you’re installing an above-ground pool, cushion sand goes inside the pool’s footprint, directly under the liner. Most pool manufacturers recommend a 2-inch layer of sand as the base. This protects the liner from being punctured by small stones or roots in the soil and provides a softer, more comfortable surface to walk on.
For pool installations, use masonry sand (also called washed sand), which is free of rocks and sharp debris. The sand should be leveled carefully before the liner goes in, since any bumps or dips will be visible and felt once the pool is filled with water.
How to Level and Compact It
Spreading cushion sand isn’t complicated, but getting it flat and properly compacted takes the right approach. For most DIY projects, you’ll need a few basic tools:
- Screed board or straight edge: A long, straight board (or a piece of aluminum channel) dragged across the sand surface to create a uniform, level plane. You set guide rails at your desired height and pull the screed across the top.
- Vibrating plate compactor: A machine that presses and vibrates the sand to pack it tightly. Plate compactors typically weigh 100 to 300 pounds and produce up to 10,000 vibrations per minute. They’re available for rent at most equipment rental shops.
- Hand tamper: For smaller areas or tight spaces where a plate compactor won’t fit, a flat-bottomed hand tamper works to press the sand down manually.
For slab work and pipe bedding, compaction is critical. Loose sand will settle unevenly over time, creating voids beneath slabs or allowing pipes to shift. Dampen the sand lightly before compacting, as dry sand doesn’t pack as effectively. For pool bases, compaction is less intense since you’re working with a thinner layer, but you still want the surface flat and firm.
Cost and Buying Tips
Cushion sand is sold in bulk by the ton or cubic yard at landscape supply yards, quarries, and some home improvement stores. Prices vary by region, but as a reference point, one supplier in the Rochester, New York area lists cushion sand at $38 per ton. A ton of sand covers roughly 100 square feet at a 2-inch depth, so a typical above-ground pool base or small patio project might need 1 to 3 tons.
Delivery fees add to the cost. Expect to pay $75 to $150 or more for delivery depending on the quantity and how quickly you need it. If you have a pickup truck, buying directly from a quarry or supply yard and hauling it yourself is usually cheaper. When ordering, tell the supplier what the sand is for. Asking for “cushion sand,” “bedding sand,” or “washed concrete sand” will get you the right product in most markets. Avoid unwashed fill sand or bank-run sand, which contain rocks and clay that make them unsuitable for leveling or pipe bedding.