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Putting artificial turf over existing grass saves a weekend of digging and costs you years of trouble, because the lawn underneath keeps decomposing, settling and holding water. Installation instructions from turf makers all begin the same way: strip the old surface, dig down and build a compacted base.
This page covers what happens when you skip that, whether bare dirt is any better, and what proper ground prep involves and costs.
Can you put artificial turf over existing grass?
You shouldn’t. The installation instructions for Evergrass turf from MSI Surfaces open by removing 4 to 6 inches of dirt, and a step-by-step installation walkthrough opens by cutting out the grass and vegetation down to bare soil. Neither starts with the lawn left in place.
Why the old lawn causes problems under turf
A living lawn is a layer of roots, thatch and organic matter, and none of it stays put once it’s covered. It breaks down, shrinks and leaves soft spots, which is why leftover roots and organic matter lead to uneven settling under turf.
The clearest evidence comes from a neighboring trade. When Landscape Management asked sod growers about laying new sod over an old lawn, Warren Bell of Biograss Sod Farm said the old surface holds a lot of organic matter and won’t match the new profile, so “Water will never move through the profile efficiently.” Mike Blair of Green Velvet Sod Farms added that decomposing turf can turn acidic or slimy. That article is about sod, not synthetic turf, but the mechanics under a lawn are the same, and so is the pooling water that follows.
Weeds are the other problem. The sod growers pointed out that weeds can grow through a new surface, so they should be eradicated before anything goes down.
Can artificial turf go straight over dirt?
Bare dirt is a better starting point than artificial turf over existing grass, but it still isn’t a finished base. Loose soil settles under foot traffic, and soil on its own drains slowly. That’s why the MSI instructions compact the soil first and then add crushed gravel on top, instead of laying turf on the dirt itself.
The same instructions add a warning worth remembering: don’t put plastic sheeting under the turf, because it traps water and creates new problems. Whatever goes beneath the turf has to let water through.
How to prepare the ground for artificial turf
Good prep is four jobs in order: remove, dig, build the base, and shape the slope. Done properly, it’s most of the work and most of why a turf lawn still looks flat years later.
Remove the grass and dig to the right depth
Cut out the grass with a shovel or sod cutter, and take the roots with it. Then excavate. Installers dig anywhere from 3 to 6 inches below the level you want the finished turf, depending on how thick the base will be, so measure the base first and dig to suit it.
Clear rocks, debris and old roots as you go. If you’re replacing a lawn that has sprinklers, either remove the lines entirely or remove the heads and cap the pipe below the rising, as MSI describes.
Weed barrier: what to use and what to avoid
A permeable weed barrier goes over the compacted soil, with seams overlapped by 6 to 8 inches and secured with landscape staples every few feet. Gopher wire is optional, and worth considering if rodents are common where you live.
Skip solid plastic. For dog areas, the SitePrep walkthrough suggests leaving the barrier out or using a more permeable one, since a barrier can trap odors.
Build and compact the base
The artificial turf base is crushed gravel or road base, laid 2 to 4 inches deep in total. MSI calls for compacting it in layers of 3 to 4 inches with a 5000 lb plate compactor, and says a little water can help it pack down. SitePrep adds that overlapping passes work best and that you should recheck the slope with a level before any turf goes down.
A hand tamper will do on a tiny patch. On anything lawn-sized, a plate compactor is the tool that gets the base firm enough not to settle.
Slope the base so water drains away
Artificial turf drainage depends on a gentle fall, not on the turf itself. Aim for a slope of 1 to 2 percent, about 1 to 2 inches over every 10 feet, running away from the house and toward a drainage area. A flat base leaves water standing, and a base that tilts toward a wall sends it somewhere you don’t want it.
What to check before you dig
Utilities and irrigation sit closer to the surface than most people expect, so a few checks come first.
- Call 811 before digging, since utilities run through residential areas.
- Locate irrigation and any electrical lines under the project area, as MSI warns.
- Decide what happens to sprinkler heads: remove the line or cap it.
- Confirm whether your city needs a permit for the work.
- Plan where the water will go once the base is sloped.
That last check matters because water should never flow toward a building or home, and the slope is far easier to set before the base is compacted than after.
What does ground prep add to the cost?
Photo by Andreas Berget on Pexels
Skipping prep to put artificial turf over existing grass looks cheaper on paper, but prep is a real share of any honest budget, and it’s worth pricing line by line. These per-square-foot ranges come from SitePrep’s artificial grass cost breakdown. They’re national figures, not Bay Area quotes, so use them to compare estimates rather than to predict one.
| Prep step | Cost per square foot | What it buys |
|---|---|---|
| Existing grass removal | $0.50 to $2.00 | Stripping the lawn and roots |
| Excavation and soil removal | $0.75 to $2.50 | Digging to depth and hauling away |
| Base material | $0.50 to $1.50 | Crushed stone or decomposed granite |
| Compaction and grading | $0.25 to $1.00 | A firm, sloped surface |
| Drainage system, when needed | $2 to $5 | Moving water off heavy or flat ground |
The same source says sloped sites add 50 to 75 percent to the cost, metro areas run 20 to 40 percent above national averages, and local permits add $200 to $800. For the full installed price on top of prep, see our breakdown of artificial turf cost per square foot in the Bay Area.
Ask any installer to price removal, base and drainage as separate lines. That’s the only way to compare two quotes fairly.
Should you prepare the ground yourself or hire a pro?
A small, flat, level patch with no irrigation is a reasonable DIY job, as long as you clear the grass first rather than laying artificial turf over existing grass. A full yard with a slope, sprinklers or drainage trouble usually isn’t.
SitePrep puts DIY savings at $3 to $8 per square foot, but it also warns that DIY mistakes often end up needing professional correction. A base that’s too thin or compacted unevenly shows up as ripples and puddles, and by then the turf is down.
If you’d rather not dig, compact and level it yourself, that’s what our artificial turf installation work covers. We’ve got 20+ years of experience, and we return after 30 days to ensure everything is thriving and operating smoothly. If you’re still choosing between surfaces, our comparison of artificial turf versus sod in the Bay Area lays out the trade-offs.
Frequently asked questions
How deep do you dig for artificial turf?
Between 3 and 6 inches below the level you want the finished turf, depending on how thick the base is. MSI Surfaces says to remove 4 to 6 inches, while SitePrep says 3 to 4 inches below finished grade with a 2 to 4 inch base.
What goes under artificial turf?
Everything that replaces artificial turf over existing grass: compacted soil, a permeable weed barrier and a compacted layer of crushed gravel or road base. Decomposed granite is an alternative in warm, dry climates, according to SitePrep.
Do you need a weed barrier under artificial turf?
Most installs use one, laid over the soil with seams overlapped and stapled. In dog areas, skip it or choose a more permeable type, since it can trap odors. Never use solid plastic.
How much slope does artificial turf need?
About 1 to 2 percent, roughly 1 to 2 inches per 10 feet, sloping away from the house toward where the water can drain.
Sources
- Evergrass Artificial Turf Installation Guide — MSI Surfaces
- How to Install Artificial Grass: Step-by-step — SitePrep
- Don’t double up on sod — Landscape Management
- How Much Does Artificial Grass Cost — SitePrep
Cover photo by Jean-Paul Wettstein on Pexels