Artificial Turf Base Preparation, Materials, Depths and Compaction

This page is for DIYers and homeowners comparing contractor bids who want to understand what goes under turf and why. By the end you will be able to choose a base material for your soil, set a target depth, order the right tonnage and check the finished base before any turf goes down. For the full job sequence, see how to install artificial turf.

What does the base actually do?

The base has four jobs: carry load without rutting, drain water downward and sideways, provide a smooth plane for the turf to lie on, and separate the turf from weeds and soil movement. Turf backing is thin and flexible, so it telegraphs every bump beneath it. A base that is 1/2 inch high in one spot will show as a lump in low-angle evening light.

Crushed, angular rock does this better than rounded gravel because the fractured faces lock together under compaction. Rounded pea gravel rolls under foot and never firms up, which is why it is a poor primary base for turf.

Which base material should you use?

Names vary by region, so ask your supplier for the gradation (largest stone size and how much fine material it contains) rather than relying on the label alone.

The key trade is fines versus drainage. Fines (the dust-sized portion) fill voids and make the base hard and smooth, but they also slow water. A dense road base can drain slowly enough that pet urine lingers near the surface. An open-graded clean rock drains fast but is too coarse to lay turf directly on, so it needs a fine-graded cap.

How deep should the base be?

Depth depends on how the soil behaves and how the area is used. These are our working ranges for compacted depth, not loose depth.

If your soil drains slower than about 1 inch per hour in a simple percolation test, depth alone will not solve it. See our clay soil drainage guide and sub-surface drainage before ordering rock.

How much base material do I need?

Order by the ton, and plan for compaction. Most crushed bases shrink about 20 to 30% in volume when compacted, so buy loose volume equal to the compacted depth times 1.25 to 1.3.

Our base material calculator runs these numbers for your dimensions. Check the delivery truck's minimum; many yards charge a short-load fee under 5 to 10 tons.

How do you compact a turf base properly?

Compaction is where most bases fail. A thick layer dumped and compacted once is firm on top and soft underneath, which shows up later as dips. Follow this method:

1. Compact the sub-grade first. Wet the excavated soil lightly and run the plate compactor over it. Fill soft spots with base and recompact.
2. Place base in lifts of about 2 inches. A typical residential plate compactor (roughly 150 to 200 lbs, around 3,000 to 5,000 lbs of centrifugal force) effectively compacts 2 to 4 inches of granular material. Thicker lifts leave a soft lower zone.
3. Get the moisture right. Mist each lift with a hose until it is uniformly damp, like a squeezed sponge, not puddled. Squeeze a handful: it should hold its shape without dripping water.
4. Make 2 to 3 passes per lift, overlapping each pass by a few inches, then a final pass at 90 degrees to the first. Watch the plate: when it stops leaving visible marks and starts to bounce slightly, you are near maximum density.
5. Screed and finish. After the last lift, screed with a straight board, fill lows with fine material, mist and compact again.

Too dry, and the fines cannot lubricate the stones into a tight pack. Too wet, and water fills the voids and the base pumps (goes spongy) under the plate. If you see water squeezing up, stop and let it dry for an hour or two.

A simple field check: walk across the finished base in work boots. You should leave barely a visible print. A heel that sinks more than about 1/8 inch means another pass, or more moisture, is needed.

What flatness and slope tolerances should you aim for?

Target a surface slope of 1 to 2% (1/8 to 1/4 inch per foot) away from structures, unless the base is on a deliberately flat area with sub-surface drainage. Turf does drain through its backing, but surface slope moves water during heavy storms when the base is saturated. Read how artificial turf drains for the mechanics.

For flatness, our rule of thumb is no gap greater than 1/4 inch under a 10 ft straightedge for lawns, and about 1/8 inch for putting greens. Gaps beyond that show as shadows in low sun and can collect water.

How do you check the base with a string line or laser?

String method. Drive stakes at each corner and at 8 to 10 ft intervals along long sides. Run mason's line between stakes, set at finished base height, and use a line level to build in your slope (for example, 2.4 inches drop over a 20 ft run for 1%). Measure from string to base every few feet with a tape. Cross strings diagonally to catch dish-shaped lows in the middle.

Laser method. A rotating laser level with a receiver on a grade rod lets one person check dozens of points quickly. Set the laser's slope to your target percentage, then walk a grid at roughly 3 to 5 ft spacing. Mark highs and lows with paint and correct before final compaction. Lasers rent for about $50 to $90 per day in 2026, which is worth it on yards above about 600 sq ft. Our tools and materials checklist has the full rental list.

Water test. After final compaction, lightly sprinkle the whole base and watch for 10 minutes. Any spot that stays shiny is a low. This catches what strings miss.

What most guides get wrong about base

They specify depth but not lifts. Four inches compacted in one pass is not equivalent to four inches built in two lifts. The other common miss is skipping the sub-grade: compacting rock on top of loose, freshly dug soil means the base settles as the soil beneath it consolidates. If you have a choice between an extra inch of base or properly compacting the sub-grade, compact the sub-grade. Settled bases are the most common root of standing water on turf.

Frequently asked questions

Can I use sand as a base for artificial turf?

Sand alone is a poor base. It does not lock together, so it shifts under foot traffic and washes out under heavy rain, leaving ruts and dips. Some installers use a thin sand layer on top of a crushed base for smoothing, but decomposed granite or rock dust holds its shape better for that job. Use crushed angular aggregate for the structural layer.

Is pea gravel good under turf?

Not as the main base. Pea gravel is rounded, so the stones roll against each other and never compact into a firm layer. Turf over pea gravel feels soft and develops lumps. If you need fast drainage, use clean crushed angular rock instead, capped with a finer compactable material so the surface is smooth enough for turf.

How long does it take for a turf base to set?

A crushed aggregate base is ready as soon as it is compacted and the surface has dried a little, typically a few hours. It does not cure like concrete. If you compacted it quite wet, wait until the surface is no longer shiny and does not print under your boot, so the backing and seam adhesive are not sitting on mud.

Do I need to remove all the old grass roots?

Remove the sod layer and as many runners of creeping grasses as practical, since aggressive species like Bermuda can push through gaps. You do not need to sift out every root. Fine roots decompose and the small volume loss is absorbed by compaction. Large woody roots should be cut out because they rot and leave voids.

What does base preparation cost?

Base rock typically runs about $35 to $70 per ton delivered in 2026, depending on region and load size, plus compactor rental and haul-away of excavated soil. For a professional install, excavation and base often account for roughly a third or more of the total price. See artificial turf cost for full breakdowns.