What people mess up when installing St. Augustine sod
Some folks try shortcuts, others pay for it later. Laying new sod over old grass is one of them things that sounds easy but mostly ain't that simple. It might seem like you saving time, but truth is, that shortcut can make your lawn look bad or fail altogether. Lotta folks in Texas, especially places like Fort Worth, Mansfield, and Kennedale, end up redoing it again after doing it wrong first time. So let’s talk about the facts and the messes that follow.
What Happens When You Don’t Remove Old Grass
Putting sod on top of old grass blocks oxygen. You suffocate the new roots before they even got a chance. What’s underneath is already struggling—maybe weeds, maybe dry Bermuda that ain’t been watered good. New sod needs to grab into soil, not rot on top of old patchy turf. The roots can’t push through thick dead thatch, and before you know it, you’re dealing with brown patches or mush.
Besides that, when grass starts dying underneath, it breaks down and starts creating heat and gases. That stinks—literally and financially.
Soil Contact Is Non-Negotiable
New Bermuda sod, Zoysia, or St. Augustine ain’t like carpet. You can’t roll it out and just walk off. Roots need contact with actual topsoil to survive. If the base ain't prepped right, even watering it three times a day ain’t gonna help. The soil needs to be loose enough so roots can stretch down, not sideways. You want it biting the dirt, not floating on some dead mat.
A lotta lawn care specialists—including pros at Texas Sod Zilla - won’t even install sod until old vegetation’s fully removed. And they’re right to insist on it. The prep work is where most of the success lies. Not in the laying part.
What About Just Scalping the Lawn?
Scalping or mowing it down low ain't enough. You may think taking your mower deck as low as it goes will “clear” things out. Nope. You still leaving a thick layer of roots, thatch, and compacted organic material underneath. The root zone stays choked. It’ll hold water like a sponge in some areas, dry out like sandpaper in others.
Plus, your soil pH, compactness, and drainage don’t change just cause you mowed low. You’re not correcting underlying problems like grubs, poor drainage, or nutrient imbalance. A soil test could show what’s really wrong, but you can’t test old thatch and expect accuracy.
Do You Need to Till?
Tilling ain't always necessary but sometimes it helps, especially when the soil’s real tight or full of clay. Texas soil, especially near Ellis County or Tarrant County, often got lots of clay. That stuff don’t let water pass easy. If you're laying St. Augustine sod or Zoysia sod, those roots like spreading wide, and compact dirt ain't helping 'em.
Some homeowners skip tilling to save time, but compacted areas will bounce back poorly. You could aerate instead, but that only pokes holes. Tilling actually mixes things and helps your soil breathe better. Just don’t go too deep or you’ll mess up soil layers.
Will the Old Grass Die Off Anyway?
Maybe. But it's a gamble. Old grass doesn’t always die right away, and some types like Bermuda grass got stubborn roots. They come back with heat, water, and sunlight. You think you buried it—but it rises. Then your new lawn got invaders fighting for space. That’s double trouble. Mixing Bermuda with Zoysia, for example, causes mismatched texture and growth rates. Looks patchy, uneven, and can’t be mowed right.
Weed Problems Get Worse, Not Better
Leaving old grass means leaving old weed seed too. You lay sod over it, and it becomes a hotbed for problems. Dandelions, crabgrass, and clover don’t need an invite. With sun, water, and warmth, those dormant seeds germinate right through the seams or edges. New sod don’t stand a chance unless it's thick and well-rooted, which it won’t be if you skipped the prep.
And forget about using herbicides after. You can’t throw down weed killer over fresh sod—roots too tender. So if you messed up early, you kinda stuck waiting until your sod is old enough to treat again. That could be months.
What Should You Actually Do Before Laying Sod?
Here’s what works, plain and straight:
-
Kill the existing lawn completely. Use a non-selective herbicide like glyphosate (applied properly). Then wait 10–14 days and reapply if needed.
-
Scalp it down, then remove the dead grass using a sod cutter or shovel. Don’t just leave it.
-
Till or loosen the top 2–4 inches of soil. Mix in compost or topsoil if it’s too sandy or too clay-heavy.
-
Grade it for drainage. Water should run off properly—not pool in corners.
-
Level it out. No bumps, no dips. Use a landscaping rake.
-
Do a soil test. Add lime or sulfur if your pH is too high or low.
-
Water the area once or twice so the soil settles before laying sod.
This ain’t quick. Takes real effort. But once you do it right, you’re setting the stage for a strong lawn. Your grass installation will last longer, root faster, and handle foot traffic better.
Is There Ever a Time to Lay Over Old Grass?
If you’re flipping a property and just need it to look good for a couple months—maybe. But you’re not growing a lawn. You’re just staging a surface. It’ll green up, sure, but by the next season, it's likely to go patchy. No root anchoring means your sod lifts with a rake.
Some landscapers may tell you to go ahead if the old grass is super thin and dry. Even then, most will still dethatch and loosen topsoil first. Point is, direct sod-to-grass contact rarely works out long term.
Final Thoughts
You can lay new sod over old grass, technically—but you really shouldn’t. It may look good for a week or two, but long-term? The grass fails more often than not. That’s wasted money, time, and effort. Prep work's boring, no doubt. But that’s what makes sod work right.
Do the kill-off. Level the ground. Get the soil prepped. Then and only then, your sod will root right and grow strong. If you want it done professionally, companies like Texas Sod Zilla been handling proper sod installation in Texas for years—they don’t skip corners.
Put in the work now, so you ain't fixing your lawn again in six months. Or sooner.
