What goes under artificial turf?

Five layers, from the ground up

A turf lawn is a small drainage system with a carpet on top. From the bottom up:

1. Your native soil, cleared of the old grass and graded.
2. A base of washed, compacted stone or gravel.
3. Sometimes a fabric or a pad, depending on the ground and the use.
4. The turf, with a backing that lets water through.
5. Infill, usually sand, brushed down between the blades.

Around all of it, the edges and seams are anchored so nothing lifts or shifts.

Two states have written this down, and their rules make a useful checklist even where they are not the law. North Carolina’s landscape contractor rules list five steps for installing artificial turf. Florida’s standard for single-family lawns, in force since 19 May 2026, adds rules for drainage and materials. Our guide to installer rules by state sets the North Carolina standard out in full.

The ground underneath

Everything starts with the soil you already have. North Carolina’s first step is to make sure the sub-grade is compacted and pitched properly to drain. In other words: firm, and sloped so water has somewhere to go.

Florida adds a caution that runs the other way. Its rule bars compacting the soil beneath the base so much that water can no longer soak in. The two words even differ: North Carolina’s “sub-grade” is the prepared soil, while Florida’s “subgrade” is the drainage layer the turf sits on. Either way the goal is the same. Water that passes through the turf has to leave, down into the ground or off to the side.

What your soil does with that water depends on where you live:

• Denver metro. The Colorado Geological Survey says clay here can swell up to 20% by volume when it gets wet. A base that lets water pool on that clay invites it to move.
• The coast. Under Leon sand, common in Horry County and northeast Florida, the USDA puts the water table 6 to 18 inches down for one to four months in most years. Sand drains fast until the water has nowhere left to go.

New Jersey’s environment department sums it up: a turf that drains 10 inches an hour does not mean the ground underneath will take water at that rate. Heavy clay fills up quickly, and then you get runoff.

The base

The base is the layer that keeps the surface flat and moves water away. It is usually crushed stone or gravel, spread in layers and compacted.

What goes into it matters as much as how thick it is. New Jersey’s report calls a mix of high-quality washed hard rock, sand and gravel ideal for drainage. Florida’s rule requires the material under the turf to be washed, because fine dirt in a base washes down and clogs it.

Drainage targets exist too. The Synthetic Turf Council, the industry’s trade association, suggests the base and finish stone drain at least 14 inches an hour, as cited in the New Jersey report.

Depth is where you will see the widest range of claims. The one written residential minimum we know of is Thornton’s: its rebate rules ask for at least three inches of compacted aggregate. That is a floor for one rebate program, not a design for every yard. Clay, a high water table, a slope or a dog run can all call for more, which is why the base is built for the soil, not from a template.

Fabric and pads

Some yards get a layer between the soil and the base, or between the base and the turf:

• Weed fabric. The Colorado Geological Survey discourages plastic sheeting on swelling soil because it traps moisture. It says non-woven geotextile fabric controls weeds and still lets the soil breathe.
• Shock pads. Under a play area, a pad matched to the equipment’s fall height adds cushion.

The turf and its backing

The turf itself is fibers stitched into a backing. That backing has to let water through, and New Jersey’s report says it needs enough openings for water to drain to the soil or storage below. The trade association suggests 10 inches an hour through the turf and infill. Thornton’s rebate rules set a lower floor: at least two inches an hour through the backing.

North Carolina’s standard adds a detail you can check with your own eyes: the turf is rolled out with the nap, the lean of the blades, facing one direction.

Edges, seams and infill

The last layer holds the rest in place.

• Edges. North Carolina requires a perimeter attachment system. Florida requires anchoring at all edges and seams.
• Seams. Thornton’s rules call for seams to be glued, not sewn.
• Infill. North Carolina’s standard secures the turf with an evenly weighted sand layer over the whole surface. In Florida, a single-family lawn may use only natural infill such as clean silica sand, rock or shell, and the job has to be designed so infill does not wash off the property. Our Florida infill guide covers that rule.

What to ask before anyone digs

1. What is going under the turf, layer by layer?
2. How deep is the base, and why that depth for this soil?
3. Where does the water go once it passes through: into the ground, or to a drain or the side of the yard?
4. Is the base material washed?
5. How are the edges anchored, and are the seams glued?
6. What infill, and how much?

That is how we build it. On the free visit we measure the space and check the ground. Then we prep the site, build the base for your soil, and lay, seam and edge the turf before the infill goes down.