Eager homeowners often ponder the question – can I simply lay fresh new sod right over my current, lackluster lawn to transform it instantly, or is starting completely from scratch necessary?
The appeal is obvious. Relaying sod promises a rapid makeover turning drab into fab seemingly overnight. But does placing sod over existing grass actually set up the new lawn for success, or cause issues down the line?
While it’s technically possible to lay sod over an existing lawn, it’s generally not recommended. Doing so can lead to problems such as root competition, uneven ground, increased risk of pests and diseases, and water drainage issues. For optimal results and a healthier, long-lasting lawn, it’s best to remove the old grass and prepare the soil before laying new sod.
The Drawbacks and Downsides of Laying New Sod Over Old Lawns
At first glance, skipping the intensive labor of stripping away old grass before laying new sod seems like an expedient, convenient shortcut. Simply unroll the fresh sod like a carpet directly over your tired existing lawn. But this shortcut introduces risks that may jeopardize the new sod’s quality and lifespan through:
Direct Root Competition Between Layers
With two dense layers of grass plants inhabiting the same finite soil space, intense completion arises between existing grass roots and new sod roots seeking water, nutrients, and room to spread out and develop.
This reciprocal root stress often hinders deep anchoring by the new sod, as ample space was already occupied by the old grass root mass. Poor anchoring leads to problems.
Eventual Surface Irregularities and Unevenness
While less noticeable initially, over months to years the slowly decaying old grass underneath gradually decomposes. This creates an inconsistent base of soft, sunken pockets and areas of remaining thatch that can mirror through the new sod above.
This sod subsidence results in visible depressions, pits, bumps, ridges, and sinkholes across the lawn’s surface. This makes smoothly mowing, leveling, and evenly irrigating difficult.
Transfer of Existing Pest and Disease Issues
Any preexisting issues in the old lawn such as chinch bugs, sod webworms, army worms, brown patch fungus, or other pest and disease organisms can remain active in the buried grass layer. Eventually, these may spread upward into the new sod above.
Introduction of these legacy lawn problems can be devastating, wholly defeating the goal of installing fresh sod to start clean. Monitoring and preventive treatments become more difficult with dual layers too.
Water Drainage and Root Zone Moisture Challenges
The old grass decaying into a soggy, partially decomposed layer forms a physical barrier preventing new sod roots from optimally penetrating down into deeper soil layers and absorbing stored moisture reserves.
This can lead to excess moisture getting trapped against the new sod’s bottom, while also reducing accessible water during surface drying. Drainage and moisture consistency issues result.
Laying new sod over intact existing turf imposes challenges from the onset that jeopardize the new lawn’s success. But might certain unique scenarios make sod over grass feasibly work? Let’s examine next…
The Limited Cases Where Laying Sod Over Existing Grass May Succeed
Most turfgrass experts strongly recommend removing existing vegetation entirely before installing new sod whenever possible. However, in a handful of specific situations, laying replacement sod over existing living grass may be possible:
When the Old Turf Layer is Extremely Sparse or Patchy
If old turf coverage is limited to widely spaced individual plants or small bare patchy areas with large sections of exposed dirt between, new sod roots may be able to thread down through the scattering of thin old growth to adequately anchor itself.
Penetration potential depends greatly on the density and mat development of even nominally sparse old grass though. Beware – even patchy layers can still present substantial barriers hindering deep rooting if dense thatch is present.
Over Previously Installed Fast Breakdown Grass Species
Certain warmer season grass species like zoysia break down into thatch and decompose more rapidly under new sod compared to slower rotting cool season grasses. This trait may permit new roots to penetrate down before major decomposition issues arise.
However, zoysia and other tropical grasses remain challenging to fully kill off beforehand. Leaving remnants risks continuous survival struggles between weakly surviving zoysia shoots and the intended new sod.
For Very Short Term Temporary Beautification Goals
In cases where the primary goal is simply greening up an area rapidly for a one-time event like a graduation or wedding using the most expedient method possible, laying sod over weak existing grass may provide a few weeks of temporarily improved aesthetics, after which the sod can be removed.
This very short duration skirting of potential long term lawn health repercussions may satisfy some homeowners willing to trade longevity and quality for a month or two of adequate decorative appearances from their sod.
These scenarios provide some possibility for sod over grass success, but never guarantee it. Next, we’ll examine why most professionals continue to recommend full lawn removal before new sod…
Why Most Turf Experts Still Advise Against Laying New Sod Over Old Lawns
While occasional exceptions exist, most agricultural turfgrass scientists, sod producers, and landscape professionals strongly continue to advise completely removing existing vegetation before installing new sod. Several good reasons underlie this guidance:
New Sod Never Reaches Ideal Root Depths Over Old Grass
Even in sparse grass scenarios, opportunities for new sod roots to penetrate down deeply through the old grass debris base are limited, preventing full anchoring.
This inherently inadequate rooting leaves new sod weakly anchored in place and prone to drying out, shrinking, peeling up under foot traffic, poor nutrient access, and other failures.
High Risk of Wasted Time, Effort, and Investment
If new sod laid over existing grass quickly shows signs of poor health, moisture stress, frequent mowing issues, or sections dying off, homeowners face tear out, stripping everything, and starting over.
This wasted expenditure on failed sod, plus added time and labor to ultimately begin again from scratch, defeats the original goal of shortcutting lawn removal.
Persisting Previous Lawn Problems
From thatch accumulation to chronic pest and disease issues, old lawn problems often continue resurfacing when new sod goes over old growth.
Some challenges like matting, poor drainage, and scrub grass emergence even originate specifically from the dual competing sod layers interfering with each other’s health and performance.
Optimal Conditions Rarely Possible
The particular combination of sod variety, grazing grass density, site grading, irrigation, and other factors required to potentially make sod over lawn work are rarely ideal in real residential settings.
Thus, conditions frequently fall short of the delicate balance required for success, tipping odds toward new sod struggling.
For all these reasons, most professionals continue urging full old lawn removal as the wisest investment before new sod. Now let’s examine that process…
The Ideal Process – Removing Old Grass Entirely Before New Sod
While more labor intensive on the front end, taking time to completely remove existing vegetation and rehabilitate the underlying soil before laying new sod avoids many potential pitfalls and pays off long-term.
Eliminate Existing Grass, Plants, and Weeds
Use smothering, solarizing, or chemical control methods to fully eradicate old grass, weeds, and ornamental vegetation down to bare dirt across the intended sod installation area.
This also provides the ideal opportunity to correct previous issues like heavy thatch, poor drainage, or bad grading affecting the old lawn. Start from square one.
Test and Amend Soil Accordingly
With the blank slate of exposed topsoil, collect samples from around the site and submit them for professional lab analysis. Correct any pH imbalance, lacking nutrients, compaction, or drainage issues through appropriate amendments.
Perform Best Practices for New Sod
Follow the by-the-book sod preparation, installation, watering, and follow-up care protocols for your specific grass type laid on the newly rehabilitated soil base.
With no barriers underneath, the fresh sod roots deeply, establishing a foundation for luscious lawn performance.
Replacing the old lawn completely demands more work up front. But setting this ideal foundation sustains lifetime sod performance, avoiding issues inherent laying sod over existing grass.
Have you faced the sod over existing lawn decision and can share your own experiences and insight? Please comment below to help other homeowners!
