Can You Lay Sod Over Existing Grass

At TurnKey Lawn Care, sod installation, including clearing the old lawn, is part of the landscaping work we do across the metro. If you’re replacing a tired lawn, request a free estimate and we’ll include the removal and preparation in the price.

This guide explains what happens when sod goes over an existing lawn, what LSU AgCenter recommends instead, how to clear the old grass, and how to handle the special cases, like patching a small area or working around trees.

The short answer

What happens when sod goes over old grass

New sod arrives with a thin layer of soil and a mat of short roots. For the lawn to establish, those roots have to grow down out of that thin layer and into the ground below. When there’s an old lawn in between, several problems stack up:

• The roots hit a mat of old grass and thatch instead of soil, so they struggle to anchor
• The old grass beneath dies and decomposes, leaving an uneven, spongy layer
• Pockets form where the new sod doesn’t touch the ground, and those areas dry out quickly
• Surviving weeds and grasses from the old lawn push up through the seams
• The finished surface ends up higher and lumpier than the surrounding edges

In the New Orleans heat, those dry pockets can brown out within days. Areas that do root in often sit on top of a decaying layer that holds water after storms, which St. Augustine doesn’t tolerate well.

Why weeds are an even bigger problem

Laying sod over a weedy lawn doesn’t bury the weeds. Many common lawn weeds in Louisiana spread by runners or underground stems and will grow straight up through the seams of new sod. Bermuda grass is a classic example. A UF/IFAS Extension tip on installing sod recommends removing any sod pieces infested with Bermuda grass during installation to keep it from taking over a patch of the new lawn. If Bermuda is already growing in the old lawn underneath, it has an even easier path. Clearing the area properly is the only reliable way to start a new lawn without inheriting the old lawn’s weed problems. Our guide to getting rid of weeds in your lawn covers the most common local weeds.

How to remove the old lawn

The LSU guide leaves the method up to you, noting that you can use herbicides or elbow grease and hand tools. The goal is the same either way: bare, clean soil. The main options:

Method	How it works	Good fit for
Hand tools	Cut and lift the old turf with a flat spade	Small areas and patches
Sod cutter	A rented machine slices the turf off in strips	Larger lawns with no major obstacles
Nonselective herbicide	Kill the existing vegetation, then remove the dead material	Lawns with persistent weeds, used strictly per the label

After removal, rake out roots, rocks and debris. An LSU AgCenter article on starting a southern lawn notes that tree roots and stumps left in the ground eventually decay and leave depressions in the lawn, so dig them out rather than burying them.

Prepare the soil after clearing

Removing the old lawn is only half the job. The soil underneath is often compacted and uneven from years of traffic, and it needs preparation before the new sod goes down.

1. Test the soil so any lime or fertilizer is based on what it actually needs.
2. Loosen the soil. The LSU AgCenter home lawn series recommends tilling 4 to 6 inches deep.
3. Add organic matter where the soil is heavy, up to about an inch, as the LSU sod guide suggests.
4. Grade and smooth so water drains away from the house and out of low spots.
5. Firm the surface with a light roller so the sod sits evenly.

Our post on how to prepare soil for sod in Louisiana walks through each of these steps in detail, including how to handle heavy clay.

Working around trees

Tilling close to trees can damage their roots, which is a real concern under the live oaks common in New Orleans yards. The LSU sod guide offers an alternative: near trees where tilling isn’t practical, use a rake to loosen at least the top inch of soil and work in up to an inch of organic matter such as peat moss. It’s also worth asking whether grass is the right choice under a dense canopy. St. Augustine thins in heavy shade over time, and new sod won’t change that. Our guide to the best ground cover for shady yards covers alternatives.

Patching a small area

Patching a dead spot in an otherwise healthy lawn follows the same principle on a smaller scale. An LSU AgCenter article on repairing lawns with sod recommends outlining the damaged area with straight edges, loosening and raking the soil smooth, and removing dead roots and debris before laying the new pieces. The same article makes a point that’s easy to skip: identify what caused the old grass to die and fix it first. It lists possible causes including heavy traffic, deep shade, low or wet spots, freeze, insects, disease or a spill.

• Cut a clean, straight-edged area around the damage
• Remove the dead grass, roots and debris inside it
• Loosen the soil and set it so the new sod sits level with the lawn around it
• Lay the pieces tightly together without stretching or overlapping
• Press them firmly into the soil with a roller or by walking on boards laid over them

LSU recommends watering daily for the first week until the soil beneath is wet but not saturated, then reducing gradually, and keeping traffic off the patch for at least two weeks.

Replace the lawn or repair it

Not every tired lawn needs a full replacement. Sometimes a lawn that looks bad is a healthy stand of grass held back by watering, mowing or feeding problems, and it can recover without new sod. Signs a lawn is worth trying to repair first:

• Most of the area still has living grass, even if it’s thin
• The problem started recently, after a drought, pest outbreak or disease
• Weeds are scattered rather than making up most of the lawn
• The soil drains reasonably well after rain

Signs replacement is the better investment:

• Weeds or an unwanted grass make up most of what’s growing
• Large areas are bare or dead and haven’t responded to better care
• The yard needs regrading or drainage work, which means disturbing the lawn anyway

If you’re unsure which side your lawn falls on, a close look at what’s actually growing usually settles it. A lawn that’s mostly weeds rarely turns around with better care alone.

Budgeting for removal

Removing the old lawn adds to the cost of a sod project, but it’s the part that protects the rest of the spend. National figures in Bob Vila’s sod price guide, based on HomeAdvisor data, put professional sod removal at about $0.50 to $2 per square foot. The same guide lists sod-cutter rental at about $70 to $100 a day for homeowners doing it themselves. Our post on sod cost per square foot in New Orleans covers how removal fits into the overall price of a new lawn.

When is the best time to replace a lawn

The LSU sod guide names April to October as the ideal window for laying sod in Louisiana. The LSU home lawn series adds that sod can be installed year-round but is more prone to drying out and winter injury while dormant, from October to March. Spring and early fall are the most forgiving seasons, since the sod roots in without the full stress of midsummer heat. Our page on the best time to lay sod in Louisiana compares the seasons.

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