Grass Underlayment: What It Is and Why It Matters for Artificial Lawns

When you lay down grass underlayment, a supportive layer installed beneath artificial turf to improve drainage, prevent weeds, and cushion the surface. Also known as turf underlay, it’s not just padding—it’s the foundation that keeps your synthetic lawn flat, clean, and ready for years of use. Skip it, and you’ll deal with uneven patches, muddy spots after rain, or weeds pushing through the fake grass. It’s the difference between a lawn that looks good for a season and one that holds up through winters, parties, and pet accidents.

Think of landscape fabric, a permeable barrier used to block weeds while letting water drain through as one of the most common types of underlayment. It’s not the same as plastic sheeting—you want something that breathes. Then there’s weed barrier, a heavy-duty geotextile designed to stop roots and seeds from growing up into your artificial grass. These aren’t optional extras. They’re what landscapers use when they know they’re installing a lawn that needs to last. You’ll find references to these in posts about weed control and soil prep, because even synthetic lawns need a clean slate underneath.

It’s not just about stopping weeds. A good underlayment also helps with drainage. If your garden gets soggy after rain, or if water pools near your patio, the underlayment works with the base beneath it to move that water away. That’s why posts about hard soil and soil improvement matter—even if you’re not using real grass, the ground underneath still needs to behave. Without proper underlayment, your artificial grass can sink, warp, or trap moisture that breeds mold or attracts pests.

And here’s the thing: most people don’t realize how much the underlayment affects the feel of the grass. A thin or cheap layer makes the turf feel hard underfoot, like walking on a plastic mat. A proper underlayment adds a little give—like natural soil—so it’s comfortable for kids to play on, pets to nap on, and bare feet to walk on. That’s why you’ll see mentions of sand infill in other posts. Sand works on top, but the underlayment works below. They’re a team.

You won’t find a single post here that says, "Just lay the grass on dirt." That’s because the people who wrote these guides know better. From weed-free flower beds to soil softening, every article here points to one truth: the surface you see is only half the story. What’s underneath decides whether it works—or falls apart.

Below, you’ll find real-world advice from people who’ve installed artificial grass, fixed failed installations, and learned the hard way what happens when underlayment is ignored. Whether you’re starting from scratch or fixing a problem you didn’t know you had, the answers are here—not as theory, but as lessons from the ground up.